From pluto at projectpluto.com Sun Feb 9 10:38:05 2020 From: pluto at projectpluto.com (Bill Gray) Date: Sun, 9 Feb 2020 10:38:05 -0500 Subject: [neo_followup] 2020 CY1 : Arecibo target, astrometry needed Message-ID: <27f88286-2d63-8def-573d-d54de7f94765@projectpluto.com> Hello all, It looks as if the Arecibo folks may be able to get some radar observations of this object about ten hours from "right now" (i.e., it'll be well-placed for them between about 01:40 and 03:40 UTC on 10 Feb). It's a nice, big target that passes right through their field of view. Arecibo can't be steered, so you really need your target to pass within about 18.5 degrees of the zenith. Since they're at latitude 18.3 N, that means the declination should be about zero to +37 degrees. This object will be near dec +21 at the center of the observation window, passing almost overhead. However, the last observations were from (K87) Dettelbach in Germany about a day and a half ago. The ephemeris uncertainties are not huge (they'll be about 15" one-sigma during the Arecibo observing window), but they're large enough that a few more observations would _really_ help. The object is around mag 16.5, so just about anybody can play here, even with a full moon will be only about 30 degrees away. The object is currently moving along at about 2"/second and picking up speed (it'll be nearly twice that by the time Arecibo looks at it). So good timing is of the essence here. In theory, one set of observations ought to do the trick, but I'm sort of hoping for more, just to rule out timing problems. -- Bill From pluto at projectpluto.com Sat Feb 15 13:09:58 2020 From: pluto at projectpluto.com (Bill Gray) Date: Sat, 15 Feb 2020 13:09:58 -0500 Subject: [neo_followup] C26FED2 = interesting object Message-ID: Hi folks, This object might just be a satellite. If so, it's a somewhat unusual one, in a very elongated orbit. It may be lunar ejecta passing by us, perhaps even a temporarily captured object a la 2006 RH120 = 6R10DB9. Or it could be heliocentric junk passing by us, similar to J002E3 or 2018 AV2. Further observations would be a really excellent idea. Thanks! -- Bill From pluto at projectpluto.com Sat Feb 15 19:59:38 2020 From: pluto at projectpluto.com (Bill Gray) Date: Sat, 15 Feb 2020 19:59:38 -0500 Subject: [neo_followup] C26FED2 = interesting object In-Reply-To: References: Message-ID: <1c52e38e-1724-7150-47a2-d53b0df635b2@projectpluto.com> With follow-up from (L01) Vi?njan, it's confirmed that this is a temporarily captured object. Whether it's natural or junk is unknown. I _really_ hope someone gets more data for it. If it's a temporarily captured rock, that's a Really Big Deal. -- Bill On 2/15/20 1:09 PM, Bill Gray wrote: > Hi folks, > > ?? This object might just be a satellite.? If so,? it's a > somewhat unusual one,? in a very elongated orbit.? It may be > lunar ejecta passing by us,? perhaps even a temporarily captured > object a la 2006 RH120 = 6R10DB9.? Or it could be heliocentric > junk passing by us,? similar to J002E3 or 2018 AV2.? Further > observations would be a really excellent idea. > > Thanks!?????????????? -- Bill From planetaryscience at yahoo.com Sun Feb 16 01:20:14 2020 From: planetaryscience at yahoo.com (Sam Deen) Date: Sun, 16 Feb 2020 06:20:14 +0000 (UTC) Subject: [neo_followup] C26FED2 = interesting object In-Reply-To: <1c52e38e-1724-7150-47a2-d53b0df635b2@projectpluto.com> References: <1c52e38e-1724-7150-47a2-d53b0df635b2@projectpluto.com> Message-ID: <1105329370.3618909.1581834014927@mail.yahoo.com> I'm leaning on rock, personally. The current orbit gives an Area/mass ratio of 2.8 +/- 8.0 m^2/kg, which obviously is very far from conclusive, but seems to point towards the object not being artificial. For comparisons, here are a few AMRs according to Bill's distant artsat pseudo-mpec catalog: 6Q0B44E/XL8D89E: 0.028 m^2/kgISO Rk: 0.024 m^2/kg TESS: 0.023 m^2/kg S510923: 0.014 m^2/kg2019-040B: 0.013 m^2/kg1999-066B: 0.012 m^2/kg 2018-103B: 0.012 m^2/kgWT1190F: 0.011 m^2/kg1999-040D: 0.010 m^2/kg IMP-8: 0.010 m^2/kgGeotail: 0.007 m^2/kg S509559: <0.003 m^2/kg Im not sure how to use find_orb to force-fit test AMR values, but I suppose that even with a poorly-defined orbit, being able to demonstrate its AMR is over 0.05 m^2/kg would make it most likely not an artsat in my opinion at least. Additionally, the aphelion of this thing is seriously impressively large. Its aphelion is recorded at 0.0148 +/- 0.0005 AU, which is larger than the radius of Earth's hill sphere at ~0.010004 AU. I assume find_orb wouldn't be giving a geocentric orbit if it was orbiting faster than escape velocity, though. Running the orbit forwards shows it won't be staying in geocentric orbit for long, at least nominally. The radial velocity will reach its minimum around April 7, at which point I assume the gravitational hold of the sun will start to take over, and it will move back into heliocentric orbit. Running the orbit backwards nominally says it's been in orbit since February 13 2018, putting it as having orbited us for around 2 years by now. Of course, that's massively premature to conclude with only half a day's worth of observations. All I can say for sure is that it's orbiting us right now, and was almost surely orbiting us since the November perigee. In regards to ephemerides: C26FED2 would have been above magnitude 23 since February 10, although with a low enough elongation that would have made detection improbable. The first time it really would have been detectable was on February 13 when it peaked around magnitude ~16-17 at an elongation of 124 degrees. It has been slowly dimming ever since, and will remain above magnitude 23 until February 26. I would give it good chances of at least a couple other observatories spotting it over the coming days. It's a shame the orbital period is so long, though. Once it stops being visible on February 26, it won't be coming back.. So, the next few days are all we have to figure out more about this weird object. Hopefully some larger scopes will get pointed at it in that time! ~Sam On Saturday, February 15, 2020, 5:59:52 PM MST, Bill Gray wrote: ? ? With follow-up from (L01) Vi?njan,? it's confirmed that this is a temporarily captured object.? Whether it's natural or junk is unknown.? I _really_ hope someone gets more data for it.? If it's a temporarily captured rock,? that's a Really Big Deal. -- Bill On 2/15/20 1:09 PM, Bill Gray wrote: > Hi folks, > >? ?? This object might just be a satellite.? If so,? it's a > somewhat unusual one,? in a very elongated orbit.? It may be > lunar ejecta passing by us,? perhaps even a temporarily captured > object a la 2006 RH120 = 6R10DB9.? Or it could be heliocentric > junk passing by us,? similar to J002E3 or 2018 AV2.? Further > observations would be a really excellent idea. > > Thanks!?????????????? -- Bill -- neo_followup mailing list neo_followup at projectpluto.com http://projectpluto.com/mailman/listinfo/neo_followup_projectpluto.com -------------- next part -------------- An HTML attachment was scrubbed... URL: From pluto at projectpluto.com Sun Feb 16 10:11:04 2020 From: pluto at projectpluto.com (Bill Gray) Date: Sun, 16 Feb 2020 10:11:04 -0500 Subject: [neo_followup] C26FED2 = interesting object In-Reply-To: <1105329370.3618909.1581834014927@mail.yahoo.com> References: <1c52e38e-1724-7150-47a2-d53b0df635b2@projectpluto.com> <1105329370.3618909.1581834014927@mail.yahoo.com> Message-ID: <1eed3d9c-b357-4360-fcae-731a2252d3c6@projectpluto.com> On 2/16/20 1:20 AM, Sam Deen wrote: > I'm leaning on rock, personally. I expect to remain in the "insufficient data" camp for quite a while. It's unlikely that we'll get enough astrometry to tell. > The current orbit gives an Area/mass ratio of 2.8 +/- 8.0 m^2/kg, which obviously is very far from conclusive, Extremely inconclusive. The object could have the effectively zero AMR of a rock. Or it could have the 5.6 m^2/kg of an empty trash bag object, and the residuals would be the same. Or anywhere in between and still fit the available data. We're up to 19 observations as I write this, which has brought the AMR to 0.13 +/- 0.51. If it's artificial, an AMR of, say, 0.02 would probably be in the right ballpark for a piece of junk this size. I don't think it's an ETBO, because something that light would have a tough time staying in orbit around us; solar radiation pressure would push it out into an heliocentric orbit... actually, then into interstellar space; ETBOs are that light. but seems to point towards the object not being artificial. For comparisons, here are a few AMRs according to Bill's distant artsat pseudo-mpec catalog: Yes, but we also have, for example, ZTF00V9 = ZTF00Vv = ZTF00Y5 = ZTF00Yq, with an area/mass ratio of 107 +/- 3 m^2/kg : https://www.projectpluto.com/pluto/mpecs/ztf00v9.htm#etbo and many in between. I've learned, mostly over the last couple of years, that artsats come with a fairly bewildering range of area/mass ratios. (I'd previously assumed such high AMRs must be bogus, and that I had bad data or data for two or three different objects, or that it was maneuvering. Once I started looking for ETBOs, I realized they were everywhere. One, 'Multijunk', has been a "discovery" on NEOCP at least two dozen times.) > Im not sure how to use find_orb to force-fit test AMR values, You can apply a constraint of, say, "A=0.005", much as you would constrain "e=1" if you thought it was a comet or "a=5.2,e=0" for a circular Jupiter Trojan orbit. but I suppose that even with a poorly-defined orbit, being able to demonstrate its AMR is over 0.05 m^2/kg would make it most likely not an artsat in my opinion at least. If you find, say, AMR = 0.020 +/- 0.001, _then_ you've got evidence it's an artsat, with the uncertainty in the value significantly less than the value itself. Proving something is _not_ an artsat is a lot harder. Tell me you've got AMR = 0.001 +/- 0.010, and I'll just say that an AMR of 0.01 would fit within that uncertainty, so it _could_ be an artsat, roughly as likely as being a rock. Getting an accurate AMR for a rock has happened... in fact, for 2006 RH120 (only confirmed temporarily captured rock), we got AMR = (98.5 +/- 2)E-5 m^2/kg. That object, however, did three orbits over most of a year, and we got a radar observation on it. Unless we get far more precovery data than I expect, astrometry isn't going to tell us if this is a rock or not. Radar data might -- for example, with 2018 AV2, we not only measured a high AMR; Arecibo got a stronger radar echo from it than would be expected for a rock. Or spectroscopy, as happened initially with J002E3 (it had the spectral signature of titanium dioxide paint). Or infrared data; if the albedo is near 100%, you start to think about an object with white TiO2 paint. > > Additionally, the aphelion of this thing is seriously impressively large. Its aphelion is recorded at 0.0148 +/- 0.0005 AU, which is larger than the radius of Earth's hill sphere at ~0.010004 AU. I assume find_orb wouldn't be giving a geocentric orbit if it was orbiting faster than escape velocity, though. It would, but with e > 1. (In Settings, you can choose the reference object. The default 'automatic' setting gets you a geocentric orbit if the object is within the earth's sphere of influence, a selenocentric orbit if it's with the moon's sphere of influence, etc. But you can, for example, insist on a Neptune-centric orbit for an object that is nowhere near Neptune.) Running the orbit forwards shows it won't be staying in geocentric orbit for long, at least nominally. The radial velocity will reach its minimum around April 7, at which point I assume the gravitational hold of the sun will start to take over, and it will move back into heliocentric orbit. Running the orbit backwards nominally says it's been in orbit since February 13 2018, putting it as having orbited us for around 2 years by now. Of course, that's massively premature to conclude with only half a day's worth of observations. All I can say for sure is that it's orbiting us > right now, and was almost surely orbiting us since the November perigee. I think there may have been some previous perigees, but yeah, we don't have enough data yet to say. > > In regards to ephemerides: > > C26FED2 would have been above magnitude 23 since February 10, although with a low enough elongation that would have made detection improbable. The first time it really would have been detectable was on February 13 when it peaked around magnitude ~16-17 at an elongation of 124 degrees. It has been slowly dimming ever since, and will remain above magnitude 23 until February 26. > > I would give it good chances of at least a couple other observatories spotting it over the coming days. It's a shame the orbital period is so long, though. Once it stops being visible on February 26, it won't be coming back.. So, the next few days are all we have to figure out more about this weird object. Hopefully some larger scopes will get pointed at it in that time! > > ~Sam > On Saturday, February 15, 2020, 5:59:52 PM MST, Bill Gray wrote: > > > ? ? With follow-up from (L01) Vi?njan,? it's confirmed that this > is a temporarily captured object.? Whether it's natural or junk > is unknown.? I _really_ hope someone gets more data for it.? If > it's a temporarily captured rock,? that's a Really Big Deal. > > -- Bill > > On 2/15/20 1:09 PM, Bill Gray wrote: > > Hi folks, > > > >? ?? This object might just be a satellite.? If so,? it's a > > somewhat unusual one,? in a very elongated orbit.? It may be > > lunar ejecta passing by us,? perhaps even a temporarily captured > > object a la 2006 RH120 = 6R10DB9.? Or it could be heliocentric > > junk passing by us,? similar to J002E3 or 2018 AV2.? Further > > observations would be a really excellent idea. > > > > Thanks!?????????????? -- Bill > > -- > neo_followup mailing list > neo_followup at projectpluto.com > http://projectpluto.com/mailman/listinfo/neo_followup_projectpluto.com From planetaryscience at yahoo.com Sun Feb 16 12:35:25 2020 From: planetaryscience at yahoo.com (Sam Deen) Date: Sun, 16 Feb 2020 17:35:25 +0000 (UTC) Subject: [neo_followup] {MPML} C26FED2 = interesting object In-Reply-To: <1eed3d9c-b357-4360-fcae-731a2252d3c6@projectpluto.com> References: <1c52e38e-1724-7150-47a2-d53b0df635b2@projectpluto.com> <1105329370.3618909.1581834014927@mail.yahoo.com> <1eed3d9c-b357-4360-fcae-731a2252d3c6@projectpluto.com> Message-ID: <472829551.3716448.1581874525109@mail.yahoo.com> My bad... noticed far too late that a large AMR makes an object empty trash baggy, and not more like a solid object. Ignore my comments on the current AMR estimate, they were definitely far too premature to say much of anything. On Sunday, February 16, 2020, 8:11:17 AM MST, Bill J. Gray wrote: On 2/16/20 1:20 AM, Sam Deen wrote: > I'm leaning on rock, personally. ? ? I expect to remain in the "insufficient data" camp for quite a while.? It's unlikely that we'll get enough astrometry to tell. > The current orbit gives an Area/mass ratio of 2.8 +/- 8.0 m^2/kg, which obviously is very far from conclusive, ? ? Extremely inconclusive.? The object could have the effectively zero AMR of a rock.? Or it could have the 5.6 m^2/kg of an empty trash bag object,? and the residuals would be the same.? Or anywhere in between and still fit the available data. ? ? We're up to 19 observations as I write this,? which has brought the AMR to 0.13 +/- 0.51.? If it's artificial,? an AMR of,? say,? 0.02 would probably be in the right ballpark for a piece of junk this size.? I don't think it's an ETBO, because something that light would have a tough time staying in orbit around us;? solar radiation pressure would push it out into an heliocentric orbit... actually,? then into interstellar space;? ETBOs are that light. but seems to point towards the object not being artificial. For comparisons, here are a few AMRs according to Bill's distant artsat pseudo-mpec catalog: ? ? Yes,? but we also have,? for example,? ZTF00V9 = ZTF00Vv = ZTF00Y5 = ZTF00Yq,? with an area/mass ratio of 107 +/- 3 m^2/kg : https://www.projectpluto.com/pluto/mpecs/ztf00v9.htm#etbo ? ? and many in between.? I've learned,? mostly over the last couple of years,? that artsats come with a fairly bewildering range of area/mass ratios.? (I'd previously assumed such high AMRs must be bogus,? and that I had bad data or data for two or three different objects,? or that it was maneuvering. Once I started looking for ETBOs,? I realized they were everywhere.? One,? 'Multijunk',? has been a "discovery" on NEOCP at least two dozen times.) > Im not sure how to use find_orb to force-fit test AMR values, ? ? You can apply a constraint of,? say,? "A=0.005",? much as you would constrain "e=1" if you thought it was a comet or "a=5.2,e=0" for a circular Jupiter Trojan orbit. ? but I suppose that even with a poorly-defined orbit, being able to demonstrate its AMR is over 0.05 m^2/kg would make it most likely not an artsat in my opinion at least. ? ? If you find,? say,? AMR = 0.020 +/- 0.001,? _then_ you've got evidence it's an artsat,? with the uncertainty in the value significantly less than the value itself.? Proving something is _not_ an artsat is a lot harder.? Tell me you've got AMR = 0.001 +/- 0.010,? and I'll just say that an AMR of 0.01 would fit within that uncertainty,? so it _could_ be an artsat,? roughly as likely as being a rock. ? ? Getting an accurate AMR for a rock has happened... in fact,? for 2006 RH120 (only confirmed temporarily captured rock),? we got AMR = (98.5 +/- 2)E-5 m^2/kg.? That object, however,? did three orbits over most of a year,? and we got a radar observation on it.? Unless we get far more precovery data than I expect,? astrometry isn't going to tell us if this is a rock or not.? Radar data might -- for example, with 2018 AV2,? we not only measured a high AMR;? Arecibo got a stronger radar echo from it than would be expected for a rock.? Or spectroscopy,? as happened initially with J002E3 (it had the spectral signature of titanium dioxide paint).? Or infrared data;? if the albedo is near 100%, you start to think about an object with white TiO2 paint. > > Additionally, the aphelion of this thing is seriously impressively large. Its aphelion is recorded at 0.0148 +/- 0.0005 AU, which is larger than the radius of Earth's hill sphere at ~0.010004 AU. I assume find_orb wouldn't be giving a geocentric orbit if it was orbiting faster than escape velocity, though. ? ? It would,? but with e > 1.? (In Settings,? you can choose the reference object.? The default 'automatic' setting gets you a geocentric orbit if the object is within the earth's sphere of influence,? a selenocentric orbit if it's with the moon's sphere of influence,? etc. But you can,? for example,? insist on a Neptune-centric orbit for an object that is nowhere near Neptune.) ? Running the orbit forwards shows it won't be staying in geocentric orbit for long, at least nominally. The radial velocity will reach its minimum around April 7, at which point I assume the gravitational hold of the sun will start to take over, and it will move back into heliocentric orbit. Running the orbit backwards nominally says it's been in orbit since February 13 2018, putting it as having orbited us for around 2 years by now. Of course, that's massively premature to conclude with only half a day's worth of observations. All I can say for sure is that it's orbiting us > right now, and was almost surely orbiting us since the November perigee. ? ? I think there may have been some previous perigees,? but yeah,? we don't have enough data yet to say. > > In regards to ephemerides: > > C26FED2 would have been above magnitude 23 since February 10, although with a low enough elongation that would have made detection improbable. The first time it really would have been detectable was on February 13 when it peaked around magnitude ~16-17 at an elongation of 124 degrees. It has been slowly dimming ever since, and will remain above magnitude 23 until February 26. > > I would give it good chances of at least a couple other observatories spotting it over the coming days. It's a shame the orbital period is so long, though. Once it stops being visible on February 26, it won't be coming back.. So, the next few days are all we have to figure out more about this weird object. Hopefully some larger scopes will get pointed at it in that time! > > ~Sam > On Saturday, February 15, 2020, 5:59:52 PM MST, Bill Gray wrote: > > >? ? ? With follow-up from (L01) Vi?njan,? it's confirmed that this > is a temporarily captured object.? Whether it's natural or junk > is unknown.? I _really_ hope someone gets more data for it.? If > it's a temporarily captured rock,? that's a Really Big Deal. > > -- Bill > > On 2/15/20 1:09 PM, Bill Gray wrote: >? > Hi folks, >? > >? >? ?? This object might just be a satellite.? If so,? it's a >? > somewhat unusual one,? in a very elongated orbit.? It may be >? > lunar ejecta passing by us,? perhaps even a temporarily captured >? > object a la 2006 RH120 = 6R10DB9.? Or it could be heliocentric >? > junk passing by us,? similar to J002E3 or 2018 AV2.? Further >? > observations would be a really excellent idea. >? > >? > Thanks!?????????????? -- Bill > > -- > neo_followup mailing list > neo_followup at projectpluto.com > http://projectpluto.com/mailman/listinfo/neo_followup_projectpluto.com -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#35363): https://groups.io/g/mpml/message/35363 Mute This Topic: https://groups.io/mt/71319863/2027585 -=-=- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Posts to this list or information found within may be freely used, with the stipulation that MPML and the originating author are cited as the source of the information. -=-=- Group Owner: mpml+owner at groups.io Unsubscribe: https://groups.io/g/mpml/unsub [planetaryscience at yahoo.com] -=-=-=-=-=-=-=-=-=-=-=- -------------- next part -------------- An HTML attachment was scrubbed... URL: From planetaryscience at yahoo.com Mon Feb 17 02:53:33 2020 From: planetaryscience at yahoo.com (Sam Deen) Date: Mon, 17 Feb 2020 07:53:33 +0000 (UTC) Subject: [neo_followup] {MPML} C26FED2 = interesting object In-Reply-To: <15F3F2806A69F552.2600@groups.io> References: <1c52e38e-1724-7150-47a2-d53b0df635b2@projectpluto.com> <1105329370.3618909.1581834014927@mail.yahoo.com> <1eed3d9c-b357-4360-fcae-731a2252d3c6@projectpluto.com> <15F3F2806A69F552.2600@groups.io> Message-ID: <251369318.3921579.1581926013238@mail.yahoo.com> Here's an update on the analysis with ~1.5 days of observations: Regarding the orbital evolution: The following perihelia have definitely, no-question taken place: 2019/03/23 (q = 4,300 +/- 7,600 km, e = 0.999 +/- 0.016) 2019/06/22 (q = 309,000 +/- 11,000 km, e = 0.632 +/- 0.017) 2019/09/03 (q = 341,000 +/- 24,000 km, e = 0.636 +/- 0.014) 2019/11/18 (q = 298,200 +/- 5,900 km, e = 0.7146 +/- 0.0073) 2020/02/13 (q = 47,061 +/- 22 km, e = 0.959661 +/- 0.000064)[ejected by April 2020] The object has definitely been orbiting us since the 2019/03/23 perigee at least, but unfortunately a close approach with the Moon between then and the next perigee combined with the resultant retroactive low perigee creates a gravitational keyhole that makes it really difficult to figure out what happened before. I very much doubt any of the orbits having it launching from Earth are true, since there's no way an object would be launched from the surface directly to a barely-bound orbit without any kind of reports on it. Not to mention that nothing above geosynchronous orbit was launched in March 2019. Beresheet was launched on 22 February to the Moon, but the projected orbit of this object doesn't really fit with a Feb 22 launch at all. I could analyze its possible "launch" path, but I expect it wouldn't be very helpful at all. Regarding the AMR and telling if it's an artsat or not: The AMR has been constrained to a somewhat nonsensical -0.016 +/- 0.067 m^2/kg (read: <0.051 m^2/kg) which rules out it being one of Bill's so-called ETBOs, but still leaves it firmly in the realm of possible artsat bits. Also, although the object has only been observed between elongations of ~128 and ~133 degrees, I suppose it's worth mentioning that it hasn't displayed any massive differences in brightness with phase or with time. The most consistent observer, L01, recorded its brightness as varying by only 0.2 magnitudes over the 5 observations made of it on 02/16 over 15 minutes, and 0.4 magnitudes over the 3 observations made of it on 02/17 over 20 minutes. Of course depending on the exact exposure length, this seems to imply that C26FED2 does not have a drastic, chaotic light curve like tumbling artsats tend to have. Just as a disclaimer, though, all of this is very preliminary and absolutely subject to being incorrect. Many thanks to all of the people who have gone to the effort of observing this object in recent days! Hopefully a handful more over the next few days should let us peer past the 2019/03/23 keyhole and see if it's been here a while, or just got captured. ~Sam On Sunday, February 16, 2020, 10:35:30 AM MST, Sam Deen via Groups.Io wrote: My bad... noticed far too late that a large AMR makes an object empty trash baggy, and not more like a solid object. Ignore my comments on the current AMR estimate, they were definitely far too premature to say much of anything. On Sunday, February 16, 2020, 8:11:17 AM MST, Bill J. Gray wrote: On 2/16/20 1:20 AM, Sam Deen wrote: > I'm leaning on rock, personally. ? ? I expect to remain in the "insufficient data" camp for quite a while.? It's unlikely that we'll get enough astrometry to tell. > The current orbit gives an Area/mass ratio of 2.8 +/- 8.0 m^2/kg, which obviously is very far from conclusive, ? ? Extremely inconclusive.? The object could have the effectively zero AMR of a rock.? Or it could have the 5.6 m^2/kg of an empty trash bag object,? and the residuals would be the same.? Or anywhere in between and still fit the available data. ? ? We're up to 19 observations as I write this,? which has brought the AMR to 0.13 +/- 0.51.? If it's artificial,? an AMR of,? say,? 0.02 would probably be in the right ballpark for a piece of junk this size.? I don't think it's an ETBO, because something that light would have a tough time staying in orbit around us;? solar radiation pressure would push it out into an heliocentric orbit... actually,? then into interstellar space;? ETBOs are that light. but seems to point towards the object not being artificial. For comparisons, here are a few AMRs according to Bill's distant artsat pseudo-mpec catalog: ? ? Yes,? but we also have,? for example,? ZTF00V9 = ZTF00Vv = ZTF00Y5 = ZTF00Yq,? with an area/mass ratio of 107 +/- 3 m^2/kg : https://www.projectpluto.com/pluto/mpecs/ztf00v9.htm#etbo ? ? and many in between.? I've learned,? mostly over the last couple of years,? that artsats come with a fairly bewildering range of area/mass ratios.? (I'd previously assumed such high AMRs must be bogus,? and that I had bad data or data for two or three different objects,? or that it was maneuvering. Once I started looking for ETBOs,? I realized they were everywhere.? One,? 'Multijunk',? has been a "discovery" on NEOCP at least two dozen times.) > Im not sure how to use find_orb to force-fit test AMR values, ? ? You can apply a constraint of,? say,? "A=0.005",? much as you would constrain "e=1" if you thought it was a comet or "a=5.2,e=0" for a circular Jupiter Trojan orbit. ? but I suppose that even with a poorly-defined orbit, being able to demonstrate its AMR is over 0.05 m^2/kg would make it most likely not an artsat in my opinion at least. ? ? If you find,? say,? AMR = 0.020 +/- 0.001,? _then_ you've got evidence it's an artsat,? with the uncertainty in the value significantly less than the value itself.? Proving something is _not_ an artsat is a lot harder.? Tell me you've got AMR = 0.001 +/- 0.010,? and I'll just say that an AMR of 0.01 would fit within that uncertainty,? so it _could_ be an artsat,? roughly as likely as being a rock. ? ? Getting an accurate AMR for a rock has happened... in fact,? for 2006 RH120 (only confirmed temporarily captured rock),? we got AMR = (98.5 +/- 2)E-5 m^2/kg.? That object, however,? did three orbits over most of a year,? and we got a radar observation on it.? Unless we get far more precovery data than I expect,? astrometry isn't going to tell us if this is a rock or not.? Radar data might -- for example, with 2018 AV2,? we not only measured a high AMR;? Arecibo got a stronger radar echo from it than would be expected for a rock.? Or spectroscopy,? as happened initially with J002E3 (it had the spectral signature of titanium dioxide paint).? Or infrared data;? if the albedo is near 100%, you start to think about an object with white TiO2 paint. > > Additionally, the aphelion of this thing is seriously impressively large. Its aphelion is recorded at 0.0148 +/- 0.0005 AU, which is larger than the radius of Earth's hill sphere at ~0.010004 AU. I assume find_orb wouldn't be giving a geocentric orbit if it was orbiting faster than escape velocity, though. ? ? It would,? but with e > 1.? (In Settings,? you can choose the reference object.? The default 'automatic' setting gets you a geocentric orbit if the object is within the earth's sphere of influence,? a selenocentric orbit if it's with the moon's sphere of influence,? etc. But you can,? for example,? insist on a Neptune-centric orbit for an object that is nowhere near Neptune.) ? Running the orbit forwards shows it won't be staying in geocentric orbit for long, at least nominally. The radial velocity will reach its minimum around April 7, at which point I assume the gravitational hold of the sun will start to take over, and it will move back into heliocentric orbit. Running the orbit backwards nominally says it's been in orbit since February 13 2018, putting it as having orbited us for around 2 years by now. Of course, that's massively premature to conclude with only half a day's worth of observations. All I can say for sure is that it's orbiting us > right now, and was almost surely orbiting us since the November perigee. ? ? I think there may have been some previous perigees,? but yeah,? we don't have enough data yet to say. > > In regards to ephemerides: > > C26FED2 would have been above magnitude 23 since February 10, although with a low enough elongation that would have made detection improbable. The first time it really would have been detectable was on February 13 when it peaked around magnitude ~16-17 at an elongation of 124 degrees. It has been slowly dimming ever since, and will remain above magnitude 23 until February 26. > > I would give it good chances of at least a couple other observatories spotting it over the coming days. It's a shame the orbital period is so long, though. Once it stops being visible on February 26, it won't be coming back.. So, the next few days are all we have to figure out more about this weird object. Hopefully some larger scopes will get pointed at it in that time! > > ~Sam > On Saturday, February 15, 2020, 5:59:52 PM MST, Bill Gray wrote: > > >? ? ? With follow-up from (L01) Vi?njan,? it's confirmed that this > is a temporarily captured object.? Whether it's natural or junk > is unknown.? I _really_ hope someone gets more data for it.? If > it's a temporarily captured rock,? that's a Really Big Deal. > > -- Bill > > On 2/15/20 1:09 PM, Bill Gray wrote: >? > Hi folks, >? > >? >? ?? This object might just be a satellite.? If so,? it's a >? > somewhat unusual one,? in a very elongated orbit.? It may be >? > lunar ejecta passing by us,? perhaps even a temporarily captured >? > object a la 2006 RH120 = 6R10DB9.? Or it could be heliocentric >? > junk passing by us,? similar to J002E3 or 2018 AV2.? Further >? > observations would be a really excellent idea. >? > >? > Thanks!?????????????? -- Bill > > -- > neo_followup mailing list > neo_followup at projectpluto.com > http://projectpluto.com/mailman/listinfo/neo_followup_projectpluto.com _._,_._,_Groups.io Links: You receive all messages sent to this group. View/Reply Online (#35364) | Reply To Sender | Reply To Group| Mute This Topic| New Topic ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Posts to this list or information found within may be freely used, with the stipulation that MPML and the originating author are cited as the source of the information.Your Subscription |Contact Group Owner |Unsubscribe [planetaryscience at yahoo.com] _._,_._,_ -------------- next part -------------- An HTML attachment was scrubbed... URL: From planetaryscience at yahoo.com Tue Feb 18 15:14:01 2020 From: planetaryscience at yahoo.com (Sam Deen) Date: Tue, 18 Feb 2020 20:14:01 +0000 (UTC) Subject: [neo_followup] {MPML} C26FED2 = interesting object In-Reply-To: <15F4215553713F89.5373@groups.io> References: <1c52e38e-1724-7150-47a2-d53b0df635b2@projectpluto.com> <1105329370.3618909.1581834014927@mail.yahoo.com> <1eed3d9c-b357-4360-fcae-731a2252d3c6@projectpluto.com> <15F3F2806A69F552.2600@groups.io> <15F4215553713F89.5373@groups.io> Message-ID: <1838777901.4764841.1582056841157@mail.yahoo.com> With the newest data, it's starting to look like C26FED2 might be an artsat, due to an interesting reason. I've been trying to peer past the March (now April) perigee for a while now, and something interesting has appeared with the most recent observations. Currently, the nominal perigee distance (including free SRP parameter) is 7200 +/- 5800 km. Furthermore, find_orb has started measuring the size/mass ratio with a significance of >1 sigma, at 0.031 +/- 0.021 m^2/kg. However, with the perigee distance constrained, the size/mass ratio becomes constrained as well. q=3800 (S22.91590 W84.36982) 0.023 +/- 0.015 m^2/kg q=4000 (S26.15681 W54.32953) 0.023 +/- 0.015 m^2/kg q=4200 (S29.53229 W167.13331) 0.024 +/- 0.014 m^2/kg q=4400 (S33.03794 E95.82559) 0.024 +/- 0.014 m^2/kg q=4600 (S36.68628 E9.64050) 0.025 +/- 0.014 m^2/kg q=4800 (S40.49965 W68.35291) 0.025 +/- 0.014 m^2/kg q=5000 (S44.51065 W139.79428) 0.026 +/- 0.014 m^2/kg q=5200 (S48.76527 E154.22276) 0.027 +/- 0.014 m^2/kg q=5400 (S53.33045 E93.06067) 0.027 +/- 0.014 m^2/kg q=5600 (S58.30737 E36.38756) 0.027 +/- 0.014 m^2/kg q=5800 (S63.86060 W15.62502) 0.028 +/- 0.014 m^2/kg q=6000 (S70.28076 W61.49060) 0.028 +/- 0.014 m^2/kg q=6200 (S78.02334 W92.00780) 0.029 +/- 0.014 m^2/kg q=6300 (S81.65253 W79.61484) 0.029 +/- 0.014 m^2/kg q=6350 (S80.24785 W46.75104) 0.029 +/- 0.014 m^2/kg q=6371 (S77.71472 W35.97998) 0.029 +/- 0.014 m^2/kg q=6400 0.029 +/- 0.014 m^2/kg q=6600 0.030 +/- 0.014 m^2/kg q=6800 0.030 +/- 0.014 m^2/kg q=7000 0.031 +/- 0.014 m^2/kg Obviously the area/mass ratio is a fairly poorly constrained even for objects observed over multiple months or years, but there seems to be something to be said about the fact that higher, more reasonable perigee solution it has, the more non-gravitational movement is required. It's erratic enough that I wouldn't be certain it's artificial at this point, but the fact that for it to be a rock, it would have to come awfully, nearly impossibly, close to Earth. At any rate, assuming nothing too funky happened around the April approach, now there's a few more certain orbits before April: 2019/04/04 q = 7200 +/- 5800 km, e = 0.9927 +/- 0.00572019/01/18 q = 120,000 +/- 110,000 km, e = 0.885 +/- 0.0792018/10/25 q = 360,000 +/- 360,000 km, e = 0.65 +/- 0.30 (at which point it could have either entered Earth orbit, or been orbiting before.) ~Sam On Monday, February 17, 2020, 12:53:42 AM MST, Sam Deen via Groups.Io wrote: Here's an update on the analysis with ~1.5 days of observations: Regarding the orbital evolution: The following perihelia have definitely, no-question taken place: 2019/03/23 (q = 4,300 +/- 7,600 km, e = 0.999 +/- 0.016) 2019/06/22 (q = 309,000 +/- 11,000 km, e = 0.632 +/- 0.017) 2019/09/03 (q = 341,000 +/- 24,000 km, e = 0.636 +/- 0.014) 2019/11/18 (q = 298,200 +/- 5,900 km, e = 0.7146 +/- 0.0073) 2020/02/13 (q = 47,061 +/- 22 km, e = 0.959661 +/- 0.000064)[ejected by April 2020] The object has definitely been orbiting us since the 2019/03/23 perigee at least, but unfortunately a close approach with the Moon between then and the next perigee combined with the resultant retroactive low perigee creates a gravitational keyhole that makes it really difficult to figure out what happened before. I very much doubt any of the orbits having it launching from Earth are true, since there's no way an object would be launched from the surface directly to a barely-bound orbit without any kind of reports on it. Not to mention that nothing above geosynchronous orbit was launched in March 2019. Beresheet was launched on 22 February to the Moon, but the projected orbit of this object doesn't really fit with a Feb 22 launch at all. I could analyze its possible "launch" path, but I expect it wouldn't be very helpful at all. Regarding the AMR and telling if it's an artsat or not: The AMR has been constrained to a somewhat nonsensical -0.016 +/- 0.067 m^2/kg (read: <0.051 m^2/kg) which rules out it being one of Bill's so-called ETBOs, but still leaves it firmly in the realm of possible artsat bits. Also, although the object has only been observed between elongations of ~128 and ~133 degrees, I suppose it's worth mentioning that it hasn't displayed any massive differences in brightness with phase or with time. The most consistent observer, L01, recorded its brightness as varying by only 0.2 magnitudes over the 5 observations made of it on 02/16 over 15 minutes, and 0.4 magnitudes over the 3 observations made of it on 02/17 over 20 minutes. Of course depending on the exact exposure length, this seems to imply that C26FED2 does not have a drastic, chaotic light curve like tumbling artsats tend to have. Just as a disclaimer, though, all of this is very preliminary and absolutely subject to being incorrect. Many thanks to all of the people who have gone to the effort of observing this object in recent days! Hopefully a handful more over the next few days should let us peer past the 2019/03/23 keyhole and see if it's been here a while, or just got captured. ~Sam On Sunday, February 16, 2020, 10:35:30 AM MST, Sam Deen via Groups.Io wrote: My bad... noticed far too late that a large AMR makes an object empty trash baggy, and not more like a solid object. Ignore my comments on the current AMR estimate, they were definitely far too premature to say much of anything. On Sunday, February 16, 2020, 8:11:17 AM MST, Bill J. Gray wrote: On 2/16/20 1:20 AM, Sam Deen wrote: > I'm leaning on rock, personally. ? ? I expect to remain in the "insufficient data" camp for quite a while.? It's unlikely that we'll get enough astrometry to tell. > The current orbit gives an Area/mass ratio of 2.8 +/- 8.0 m^2/kg, which obviously is very far from conclusive, ? ? Extremely inconclusive.? The object could have the effectively zero AMR of a rock.? Or it could have the 5.6 m^2/kg of an empty trash bag object,? and the residuals would be the same.? Or anywhere in between and still fit the available data. ? ? We're up to 19 observations as I write this,? which has brought the AMR to 0.13 +/- 0.51.? If it's artificial,? an AMR of,? say,? 0.02 would probably be in the right ballpark for a piece of junk this size.? I don't think it's an ETBO, because something that light would have a tough time staying in orbit around us;? solar radiation pressure would push it out into an heliocentric orbit... actually,? then into interstellar space;? ETBOs are that light. but seems to point towards the object not being artificial. For comparisons, here are a few AMRs according to Bill's distant artsat pseudo-mpec catalog: ? ? Yes,? but we also have,? for example,? ZTF00V9 = ZTF00Vv = ZTF00Y5 = ZTF00Yq,? with an area/mass ratio of 107 +/- 3 m^2/kg : https://www.projectpluto.com/pluto/mpecs/ztf00v9.htm#etbo ? ? and many in between.? I've learned,? mostly over the last couple of years,? that artsats come with a fairly bewildering range of area/mass ratios.? (I'd previously assumed such high AMRs must be bogus,? and that I had bad data or data for two or three different objects,? or that it was maneuvering. Once I started looking for ETBOs,? I realized they were everywhere.? One,? 'Multijunk',? has been a "discovery" on NEOCP at least two dozen times.) > Im not sure how to use find_orb to force-fit test AMR values, ? ? You can apply a constraint of,? say,? "A=0.005",? much as you would constrain "e=1" if you thought it was a comet or "a=5.2,e=0" for a circular Jupiter Trojan orbit. ? but I suppose that even with a poorly-defined orbit, being able to demonstrate its AMR is over 0.05 m^2/kg would make it most likely not an artsat in my opinion at least. ? ? If you find,? say,? AMR = 0.020 +/- 0.001,? _then_ you've got evidence it's an artsat,? with the uncertainty in the value significantly less than the value itself.? Proving something is _not_ an artsat is a lot harder.? Tell me you've got AMR = 0.001 +/- 0.010,? and I'll just say that an AMR of 0.01 would fit within that uncertainty,? so it _could_ be an artsat,? roughly as likely as being a rock. ? ? Getting an accurate AMR for a rock has happened... in fact,? for 2006 RH120 (only confirmed temporarily captured rock),? we got AMR = (98.5 +/- 2)E-5 m^2/kg.? That object, however,? did three orbits over most of a year,? and we got a radar observation on it.? Unless we get far more precovery data than I expect,? astrometry isn't going to tell us if this is a rock or not.? Radar data might -- for example, with 2018 AV2,? we not only measured a high AMR;? Arecibo got a stronger radar echo from it than would be expected for a rock.? Or spectroscopy,? as happened initially with J002E3 (it had the spectral signature of titanium dioxide paint).? Or infrared data;? if the albedo is near 100%, you start to think about an object with white TiO2 paint. > > Additionally, the aphelion of this thing is seriously impressively large. Its aphelion is recorded at 0.0148 +/- 0.0005 AU, which is larger than the radius of Earth's hill sphere at ~0.010004 AU. I assume find_orb wouldn't be giving a geocentric orbit if it was orbiting faster than escape velocity, though. ? ? It would,? but with e > 1.? (In Settings,? you can choose the reference object.? The default 'automatic' setting gets you a geocentric orbit if the object is within the earth's sphere of influence,? a selenocentric orbit if it's with the moon's sphere of influence,? etc. But you can,? for example,? insist on a Neptune-centric orbit for an object that is nowhere near Neptune.) ? Running the orbit forwards shows it won't be staying in geocentric orbit for long, at least nominally. The radial velocity will reach its minimum around April 7, at which point I assume the gravitational hold of the sun will start to take over, and it will move back into heliocentric orbit. Running the orbit backwards nominally says it's been in orbit since February 13 2018, putting it as having orbited us for around 2 years by now. Of course, that's massively premature to conclude with only half a day's worth of observations. All I can say for sure is that it's orbiting us > right now, and was almost surely orbiting us since the November perigee. ? ? I think there may have been some previous perigees,? but yeah,? we don't have enough data yet to say. > > In regards to ephemerides: > > C26FED2 would have been above magnitude 23 since February 10, although with a low enough elongation that would have made detection improbable. The first time it really would have been detectable was on February 13 when it peaked around magnitude ~16-17 at an elongation of 124 degrees. It has been slowly dimming ever since, and will remain above magnitude 23 until February 26. > > I would give it good chances of at least a couple other observatories spotting it over the coming days. It's a shame the orbital period is so long, though. Once it stops being visible on February 26, it won't be coming back.. So, the next few days are all we have to figure out more about this weird object. Hopefully some larger scopes will get pointed at it in that time! > > ~Sam > On Saturday, February 15, 2020, 5:59:52 PM MST, Bill Gray wrote: > > >? ? ? With follow-up from (L01) Vi?njan,? it's confirmed that this > is a temporarily captured object.? Whether it's natural or junk > is unknown.? I _really_ hope someone gets more data for it.? If > it's a temporarily captured rock,? that's a Really Big Deal. > > -- Bill > > On 2/15/20 1:09 PM, Bill Gray wrote: >? > Hi folks, >? > >? >? ?? This object might just be a satellite.? If so,? it's a >? > somewhat unusual one,? in a very elongated orbit.? It may be >? > lunar ejecta passing by us,? perhaps even a temporarily captured >? > object a la 2006 RH120 = 6R10DB9.? Or it could be heliocentric >? > junk passing by us,? similar to J002E3 or 2018 AV2.? Further >? > observations would be a really excellent idea. >? > >? > Thanks!?????????????? -- Bill > > -- > neo_followup mailing list > neo_followup at projectpluto.com > http://projectpluto.com/mailman/listinfo/neo_followup_projectpluto.com _._,_._,_Groups.io Links: You receive all messages sent to this group. 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URL: From peter at birtwhistle.org.uk Tue Feb 18 18:38:57 2020 From: peter at birtwhistle.org.uk (Peter Birtwhistle) Date: Tue, 18 Feb 2020 23:38:57 +0000 Subject: [neo_followup] {MPML} C26FED2 = interesting object In-Reply-To: <1838777901.4764841.1582056841157@mail.yahoo.com> References: <1c52e38e-1724-7150-47a2-d53b0df635b2@projectpluto.com> <1105329370.3618909.1581834014927@mail.yahoo.com> <1eed3d9c-b357-4360-fcae-731a2252d3c6@projectpluto.com> <15F3F2806A69F552.2600@groups.io> <15F4215553713F89.5373@groups.io> <1838777901.4764841.1582056841157@mail.yahoo.com> Message-ID: <41fe3fe8-34ef-836d-8018-fcd9d7c7894d@birtwhistle.org.uk> Hi Sam, At around mag +21 my four J95 positions are treated rather optimistically in the standard FindOrb sigma.txt file. Setting their Sigma's to 0.5" (which is still probably smaller than reality) and using 36 of the 37 available observations, I get an AMR of 0.009 +/- 0.023 m^2/kg, which looks to me like rock is still very possible. I'm a little surprised it's already been pulled from the NEOCP as a "was not a minor planet". Peter J95 On 18/02/2020 20:14, Sam Deen via Groups.Io wrote: > With the newest data, it's starting to look like C26FED2 might be an > artsat, due to an interesting reason. > > I've been trying to peer past the March (now April) perigee for a > while now, and something interesting has appeared with the most recent > observations. > > Currently, the nominal perigee distance (including free SRP parameter) > is 7200 +/- 5800 km. Furthermore, find_orb has started measuring the > size/mass ratio with a significance of >1 sigma, at 0.031 +/- 0.021 > m^2/kg. However, with the perigee distance constrained, the size/mass > ratio becomes constrained as well. > > q=3800 (S22.91590 W84.36982) 0.023 +/- 0.015 m^2/kg > q=4000 (S26.15681 W54.32953) 0.023 +/- 0.015 m^2/kg > q=4200 (S29.53229 W167.13331) 0.024 +/- 0.014 m^2/kg > q=4400 (S33.03794 E95.82559) 0.024 +/- 0.014 m^2/kg > q=4600 (S36.68628 E9.64050) 0.025 +/- 0.014 m^2/kg > q=4800 (S40.49965 W68.35291) 0.025 +/- 0.014 m^2/kg > q=5000 (S44.51065 W139.79428) 0.026 +/- 0.014 m^2/kg > q=5200 (S48.76527 E154.22276) 0.027 +/- 0.014 m^2/kg > q=5400 (S53.33045 E93.06067) 0.027 +/- 0.014 m^2/kg > q=5600 (S58.30737 E36.38756) 0.027 +/- 0.014 m^2/kg > q=5800 (S63.86060 W15.62502) 0.028 +/- 0.014 m^2/kg > q=6000 (S70.28076 W61.49060) 0.028 +/- 0.014 m^2/kg > q=6200 (S78.02334 W92.00780) 0.029 +/- 0.014 m^2/kg > q=6300 (S81.65253 W79.61484) 0.029 +/- 0.014 m^2/kg > q=6350 (S80.24785 W46.75104) 0.029 +/- 0.014 m^2/kg > q=6371 (S77.71472 W35.97998) 0.029 +/- 0.014 m^2/kg > q=6400 0.029 +/- 0.014 m^2/kg > q=6600 0.030 +/- 0.014 m^2/kg > q=6800 0.030 +/- 0.014 m^2/kg > q=7000 0.031 +/- 0.014 m^2/kg > > Obviously the area/mass ratio is a fairly poorly constrained even for > objects observed over multiple months or years, but there seems to be > something to be said about the fact that higher, more reasonable > perigee solution it has, the more non-gravitational movement is > required. It's erratic enough that I wouldn't be certain it's > artificial at this point, but the fact that for it to be a rock, it > would have to come awfully, nearly impossibly, close to Earth. > > At any rate, assuming nothing too funky happened around the April > approach, now there's a few more certain orbits before April: > > 2019/04/04 q = 7200 +/- 5800 km, e = 0.9927 +/- 0.0057 > 2019/01/18 q = 120,000 +/- 110,000 km, e = 0.885 +/- 0.079 > 2018/10/25 q = 360,000 +/- 360,000 km, e = 0.65 +/- 0.30 (at which > point it could have either entered Earth orbit, or been orbiting before.) > > ~Sam > On Monday, February 17, 2020, 12:53:42 AM MST, Sam Deen via Groups.Io > wrote: > > > Here's an update on the analysis with ~1.5 days of observations: > > Regarding the orbital evolution: > > The following perihelia have definitely, no-question taken place: > > 2019/03/23 (q = 4,300 +/- 7,600 km, e = 0.999 +/- 0.016) > 2019/06/22 (q = 309,000 +/- 11,000 km, e = 0.632 +/- 0.017) > 2019/09/03 (q = 341,000 +/- 24,000 km, e = 0.636 +/- 0.014) > 2019/11/18 (q = 298,200 +/- 5,900 km, e = 0.7146 +/- 0.0073) > 2020/02/13 (q = 47,061 +/- 22 km, e = 0.959661 +/- 0.000064) > [ejected by April 2020] > > The object has definitely been orbiting us since the 2019/03/23 > perigee at least, but unfortunately a close approach with the Moon > between then and the next perigee combined with the resultant > retroactive low perigee creates a gravitational keyhole that makes it > really difficult to figure out what happened before. > > I very much doubt any of the orbits having it launching from Earth are > true, since there's no way an object would be launched from the > surface directly to a barely-bound orbit without any kind of reports > on it. Not to mention that nothing above geosynchronous orbit was > launched in March 2019. Beresheet was launched on 22 February to the > Moon, but the projected orbit of this object doesn't really fit with a > Feb 22 launch at all. I could analyze its possible "launch" path, but > I expect it wouldn't be very helpful at all. > > Regarding the AMR and telling if it's an artsat or not: > > The AMR has been constrained to a somewhat nonsensical -0.016 +/- > 0.067 m^2/kg (read: <0.051 m^2/kg) which rules out it being one of > Bill's so-called ETBOs, but still leaves it firmly in the realm of > possible artsat bits. Also, although the object has only been observed > between elongations of ~128 and ~133 degrees, I suppose it's worth > mentioning that it hasn't displayed any massive differences in > brightness with phase or with time. The most consistent observer, L01, > recorded its brightness as varying by only 0.2 magnitudes over the 5 > observations made of it on 02/16 over 15 minutes, and 0.4 magnitudes > over the 3 observations made of it on 02/17 over 20 minutes. Of course > depending on the exact exposure length, this seems to imply that > C26FED2 does not have a drastic, chaotic light curve like tumbling > artsats tend to have. Just as a disclaimer, though, all of this is > very preliminary and absolutely subject to being incorrect. > > Many thanks to all of the people who have gone to the effort of > observing this object in recent days! Hopefully a handful more over > the next few days should let us peer past the 2019/03/23 keyhole and > see if it's been here a while, or just got captured. > > ~Sam > On Sunday, February 16, 2020, 10:35:30 AM MST, Sam Deen via Groups.Io > wrote: > > > My bad... noticed far too late that a large AMR makes an object empty > trash baggy, and not more like a solid object. Ignore my comments on > the current AMR estimate, they were definitely far too premature to > say much of anything. > > On Sunday, February 16, 2020, 8:11:17 AM MST, Bill J. Gray > wrote: > > > On 2/16/20 1:20 AM, Sam Deen wrote: > > I'm leaning on rock, personally. > > ? ? I expect to remain in the "insufficient data" camp for > quite a while.? It's unlikely that we'll get enough > astrometry to tell. > > > The current orbit gives an Area/mass ratio of 2.8 +/- 8.0 m^2/kg, > which obviously is very far from conclusive, > > ? ? Extremely inconclusive.? The object could have the effectively > zero AMR of a rock.? Or it could have the 5.6 m^2/kg of an empty > trash bag object,? and the residuals would be the same.? Or > anywhere in between and still fit the available data. > > ? ? We're up to 19 observations as I write this,? which has > brought the AMR to 0.13 +/- 0.51. If it's artificial,? an > AMR of,? say,? 0.02 would probably be in the right ballpark > for a piece of junk this size.? I don't think it's an ETBO, > because something that light would have a tough time staying > in orbit around us;? solar radiation pressure would push > it out into an heliocentric orbit... actually,? then into > interstellar space;? ETBOs are that light. > > but seems to point towards the object not being artificial. For > comparisons, here are a few AMRs according to Bill's distant artsat > pseudo-mpec catalog: > > ? ? Yes,? but we also have,? for example,? ZTF00V9 = ZTF00Vv > = ZTF00Y5 = ZTF00Yq,? with an area/mass ratio of 107 +/- 3 > m^2/kg : > > https://www.projectpluto.com/pluto/mpecs/ztf00v9.htm#etbo > > ? ? and many in between.? I've learned,? mostly over the last > couple of years,? that artsats come with a fairly bewildering > range of area/mass ratios.? (I'd previously assumed such high > AMRs must be bogus,? and that I had bad data or data for > two or three different objects, or that it was maneuvering. > Once I started looking for ETBOs, I realized they were > everywhere.? One,? 'Multijunk', has been a "discovery" on > NEOCP at least two dozen times.) > > > Im not sure how to use find_orb to force-fit test AMR values, > > ? ? You can apply a constraint of,? say,? "A=0.005",? much as > you would constrain "e=1" if you thought it was a comet or > "a=5.2,e=0" for a circular Jupiter Trojan orbit. > > ? but I suppose that even with a poorly-defined orbit, being able to > demonstrate its AMR is over 0.05 m^2/kg would make it most likely not > an artsat in my opinion at least. > > ? ? If you find,? say,? AMR = 0.020 +/- 0.001,? _then_ you've > got evidence it's an artsat,? with the uncertainty in the > value significantly less than the value itself.? Proving > something is _not_ an artsat is a lot harder.? Tell me > you've got AMR = 0.001 +/- 0.010, and I'll just say that > an AMR of 0.01 would fit within that uncertainty,? so it > _could_ be an artsat,? roughly as likely as being a rock. > > ? ? Getting an accurate AMR for a rock has happened... in > fact,? for 2006 RH120 (only confirmed temporarily captured > rock),? we got AMR = (98.5 +/- 2)E-5 m^2/kg.? That object, > however,? did three orbits over most of a year,? and we got > a radar observation on it.? Unless we get far more precovery > data than I expect,? astrometry isn't going to tell us if > this is a rock or not.? Radar data might -- for example, > with 2018 AV2,? we not only measured a high AMR;? Arecibo > got a stronger radar echo from it than would be expected > for a rock.? Or spectroscopy,? as happened initially with > J002E3 (it had the spectral signature of titanium dioxide > paint).? Or infrared data;? if the albedo is near 100%, > you start to think about an object with white TiO2 paint. > > > > > Additionally, the aphelion of this thing is seriously impressively > large. Its aphelion is recorded at 0.0148 +/- 0.0005 AU, which is > larger than the radius of Earth's hill sphere at ~0.010004 AU. I > assume find_orb wouldn't be giving a geocentric orbit if it was > orbiting faster than escape velocity, though. > > ? ? It would,? but with e > 1. (In Settings,? you can > choose the reference object.? The default 'automatic' > setting gets you a geocentric orbit if the object is > within the earth's sphere of influence,? a selenocentric > orbit if it's with the moon's sphere of influence,? etc. > But you can,? for example,? insist on a Neptune-centric > orbit for an object that is nowhere near Neptune.) > > ? Running the orbit forwards shows it won't be staying in geocentric > orbit for long, at least nominally. The radial velocity will reach its > minimum around April 7, at which point I assume the gravitational hold > of the sun will start to take over, and it will move back into > heliocentric orbit. Running the orbit backwards nominally says it's > been in orbit since February 13 2018, putting it as having orbited us > for around 2 years by now. Of course, that's massively premature to > conclude with only half a day's worth of observations. All I can say > for sure is that it's orbiting us > > right now, and was almost surely orbiting us since the November perigee. > > ? ? I think there may have been some previous perigees,? but > yeah,? we don't have enough data yet to say. > > > > > In regards to ephemerides: > > > > C26FED2 would have been above magnitude 23 since February 10, > although with a low enough elongation that would have made detection > improbable. The first time it really would have been detectable was on > February 13 when it peaked around magnitude ~16-17 at an elongation of > 124 degrees. It has been slowly dimming ever since, and will remain > above magnitude 23 until February 26. > > > > I would give it good chances of at least a couple other > observatories spotting it over the coming days. It's a shame the > orbital period is so long, though. Once it stops being visible on > February 26, it won't be coming back.. So, the next few days are all > we have to figure out more about this weird object. Hopefully some > larger scopes will get pointed at it in that time! > > > > ~Sam > > On Saturday, February 15, 2020, 5:59:52 PM MST, Bill Gray > > wrote: > > > > > >? ? ? With follow-up from (L01) Vi?njan,? it's confirmed that this > > is a temporarily captured object.? Whether it's natural or junk > > is unknown.? I _really_ hope someone gets more data for it.? If > > it's a temporarily captured rock,? that's a Really Big Deal. > > > > -- Bill > > > > On 2/15/20 1:09 PM, Bill Gray wrote: > >? > Hi folks, > >? > > >? >? ?? This object might just be a satellite.? If so,? it's a > >? > somewhat unusual one, in a very elongated orbit.? It may be > >? > lunar ejecta passing by us,? perhaps even a temporarily captured > >? > object a la 2006 RH120 = 6R10DB9.? Or it could be heliocentric > >? > junk passing by us, similar to J002E3 or 2018 AV2. Further > >? > observations would be a really excellent idea. > >? > > >? > Thanks! -- Bill > > > > -- > > neo_followup mailing list > > neo_followup at projectpluto.com > > > > > http://projectpluto.com/mailman/listinfo/neo_followup_projectpluto.com > > > > > _._,_._,_ > ------------------------------------------------------------------------ > Groups.io Links: > > You receive all messages sent to this group. > > View/Reply Online (#35366) | > Reply To Sender > > | Reply To Group > > | Mute This Topic | New Topic > > > ------------------------------------------------------------------------ > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Posts to this list or information found within may be freely used, > with the stipulation that MPML and the originating author are cited as > the source of the information. > ------------------------------------------------------------------------ > Your Subscription | Contact > Group Owner | Unsubscribe > [peter at birtwhistle.org.uk] > _._,_._,_ From pluto at projectpluto.com Tue Feb 18 22:09:04 2020 From: pluto at projectpluto.com (Bill Gray) Date: Tue, 18 Feb 2020 22:09:04 -0500 Subject: [neo_followup] {MPML} C26FED2 = interesting object In-Reply-To: <1586394251.4891932.1582072587541@mail.yahoo.com> References: <1c52e38e-1724-7150-47a2-d53b0df635b2@projectpluto.com> <1105329370.3618909.1581834014927@mail.yahoo.com> <1eed3d9c-b357-4360-fcae-731a2252d3c6@projectpluto.com> <15F3F2806A69F552.2600@groups.io> <15F4215553713F89.5373@groups.io> <1838777901.4764841.1582056841157@mail.yahoo.com> <41fe3fe8-34ef-836d-8018-fcd9d7c7894d@birtwhistle.org.uk> <1586394251.4891932.1582072587541@mail.yahoo.com> Message-ID: <6cd90ae5-061c-ac41-21e0-7472984e804c@projectpluto.com> Hi Sam, I'd second the request that observations be passed on. I, for one, have definitely not lost interest in this object. Far from it. MPC is quite possibly right about this object being junk. The nominal AMR I get, with 36 of 37 observations, is 0.014 +/- 0.021 m^2/kg, which really doesn't tell you if it's a rock or not. (It mostly just rules out it being, say, a loose scrap of insulation.) If it's a rock, we can run the orbit back a few orbits with some degree of confidence that the uncertainties reflect reality. If it's junk, we really have almost no idea where it was very far back. Junk does not (usually) fit the simple SRP model over those time spans. The answer will come from more data, and I do fear that that flow of data may cease now that MPC has dropped the object from NEOCP. We may have to follow this guy all the way down to V=24 to definitively get the AMR determined. (Though there will be some hope of getting precovery observations, especially if it's a rock.) I have an inquiry in to MPC about this, but haven't heard back yet. They do, I expect, have some access to information that I lack. Such as the ability to ask around NASA and ESA and JPL folks and say, "Do you know anything about this?". They may have done so and had someone reply, "Oh yeah, we know what that is." -- Bill On 2/18/20 7:36 PM, Sam Deen wrote: > Hi Peter, > > Many thanks for the info. I had been assuming the uncertainties in all of the measurements, and probably in a handful of cases slightly underestimating them. To re-emphasize what I should have been clearer about in the original post: all of this is extremely preliminary, and prone to inaccuracy. I definitely wouldn't claim at this point that this object is certainly an artsat, it just seems to be generally leading towards being one. > > That said, if anyone has further observations of this object over the next few days, please send them here, publicly or privately! I'd like to get to the bottom of this object if at all possible, and there's still many lingering questions that I don't believe have been adequately answered by the time the MPC pulled it from the NEOCP. > > ~Sam > On Tuesday, February 18, 2020, 4:39:05 PM MST, Peter Birtwhistle wrote: > > > Hi Sam, > > At around mag +21 my four J95 positions are treated rather > optimistically in the standard FindOrb sigma.txt file. Setting their > Sigma's to 0.5" (which is still probably smaller than reality) and using > 36 of the 37 available observations, I get an AMR of 0.009 +/- 0.023 > m^2/kg, which looks to me like rock is still very possible. I'm a little > surprised it's already been pulled from the NEOCP as a "was not a minor > planet". > > Peter > J95 > > On 18/02/2020 20:14, Sam Deen via Groups.Io wrote: > > With the newest data, it's starting to look like C26FED2 might be an > > artsat, due to an interesting reason. > > > > I've been trying to peer past the March (now April) perigee for a > > while now, and something interesting has appeared with the most recent > > observations. > > > > Currently, the nominal perigee distance (including free SRP parameter) > > is 7200 +/- 5800 km. Furthermore, find_orb has started measuring the > > size/mass ratio with a significance of >1 sigma, at 0.031 +/- 0.021 > > m^2/kg. However, with the perigee distance constrained, the size/mass > > ratio becomes constrained as well. > > > > q=3800 (S22.91590 W84.36982) 0.023 +/- 0.015 m^2/kg > > q=4000 (S26.15681 W54.32953) 0.023 +/- 0.015 m^2/kg > > q=4200 (S29.53229 W167.13331) 0.024 +/- 0.014 m^2/kg > > q=4400 (S33.03794 E95.82559) 0.024 +/- 0.014 m^2/kg > > q=4600 (S36.68628 E9.64050) 0.025 +/- 0.014 m^2/kg > > q=4800 (S40.49965 W68.35291) 0.025 +/- 0.014 m^2/kg > > q=5000 (S44.51065 W139.79428) 0.026 +/- 0.014 m^2/kg > > q=5200 (S48.76527 E154.22276) 0.027 +/- 0.014 m^2/kg > > q=5400 (S53.33045 E93.06067) 0.027 +/- 0.014 m^2/kg > > q=5600 (S58.30737 E36.38756) 0.027 +/- 0.014 m^2/kg > > q=5800 (S63.86060 W15.62502) 0.028 +/- 0.014 m^2/kg > > q=6000 (S70.28076 W61.49060) 0.028 +/- 0.014 m^2/kg > > q=6200 (S78.02334 W92.00780) 0.029 +/- 0.014 m^2/kg > > q=6300 (S81.65253 W79.61484) 0.029 +/- 0.014 m^2/kg > > q=6350 (S80.24785 W46.75104) 0.029 +/- 0.014 m^2/kg > > q=6371 (S77.71472 W35.97998) 0.029 +/- 0.014 m^2/kg > > q=6400 0.029 +/- 0.014 m^2/kg > > q=6600 0.030 +/- 0.014 m^2/kg > > q=6800 0.030 +/- 0.014 m^2/kg > > q=7000 0.031 +/- 0.014 m^2/kg > > > > Obviously the area/mass ratio is a fairly poorly constrained even for > > objects observed over multiple months or years, but there seems to be > > something to be said about the fact that higher, more reasonable > > perigee solution it has, the more non-gravitational movement is > > required. It's erratic enough that I wouldn't be certain it's > > artificial at this point, but the fact that for it to be a rock, it > > would have to come awfully, nearly impossibly, close to Earth. > > > > At any rate, assuming nothing too funky happened around the April > > approach, now there's a few more certain orbits before April: > > > > 2019/04/04 q = 7200 +/- 5800 km, e = 0.9927 +/- 0.0057 > > 2019/01/18 q = 120,000 +/- 110,000 km, e = 0.885 +/- 0.079 > > 2018/10/25 q = 360,000 +/- 360,000 km, e = 0.65 +/- 0.30 (at which > > point it could have either entered Earth orbit, or been orbiting before.) > > > > ~Sam > > On Monday, February 17, 2020, 12:53:42 AM MST, Sam Deen via Groups.Io > > > wrote: > > > > > > Here's an update on the analysis with ~1.5 days of observations: > > > > Regarding the orbital evolution: > > > > The following perihelia have definitely, no-question taken place: > > > > 2019/03/23 (q = 4,300 +/- 7,600 km, e = 0.999 +/- 0.016) > > 2019/06/22 (q = 309,000 +/- 11,000 km, e = 0.632 +/- 0.017) > > 2019/09/03 (q = 341,000 +/- 24,000 km, e = 0.636 +/- 0.014) > > 2019/11/18 (q = 298,200 +/- 5,900 km, e = 0.7146 +/- 0.0073) > > 2020/02/13 (q = 47,061 +/- 22 km, e = 0.959661 +/- 0.000064) > > [ejected by April 2020] > > > > The object has definitely been orbiting us since the 2019/03/23 > > perigee at least, but unfortunately a close approach with the Moon > > between then and the next perigee combined with the resultant > > retroactive low perigee creates a gravitational keyhole that makes it > > really difficult to figure out what happened before. > > > > I very much doubt any of the orbits having it launching from Earth are > > true, since there's no way an object would be launched from the > > surface directly to a barely-bound orbit without any kind of reports > > on it. Not to mention that nothing above geosynchronous orbit was > > launched in March 2019. Beresheet was launched on 22 February to the > > Moon, but the projected orbit of this object doesn't really fit with a > > Feb 22 launch at all. I could analyze its possible "launch" path, but > > I expect it wouldn't be very helpful at all. > > > > Regarding the AMR and telling if it's an artsat or not: > > > > The AMR has been constrained to a somewhat nonsensical -0.016 +/- > > 0.067 m^2/kg (read: <0.051 m^2/kg) which rules out it being one of > > Bill's so-called ETBOs, but still leaves it firmly in the realm of > > possible artsat bits. Also, although the object has only been observed > > between elongations of ~128 and ~133 degrees, I suppose it's worth > > mentioning that it hasn't displayed any massive differences in > > brightness with phase or with time. The most consistent observer, L01, > > recorded its brightness as varying by only 0.2 magnitudes over the 5 > > observations made of it on 02/16 over 15 minutes, and 0.4 magnitudes > > over the 3 observations made of it on 02/17 over 20 minutes. Of course > > depending on the exact exposure length, this seems to imply that > > C26FED2 does not have a drastic, chaotic light curve like tumbling > > artsats tend to have. Just as a disclaimer, though, all of this is > > very preliminary and absolutely subject to being incorrect. > > > > Many thanks to all of the people who have gone to the effort of > > observing this object in recent days! Hopefully a handful more over > > the next few days should let us peer past the 2019/03/23 keyhole and > > see if it's been here a while, or just got captured. > > > > ~Sam > > On Sunday, February 16, 2020, 10:35:30 AM MST, Sam Deen via Groups.Io > > > wrote: > > > > > > My bad... noticed far too late that a large AMR makes an object empty > > trash baggy, and not more like a solid object. Ignore my comments on > > the current AMR estimate, they were definitely far too premature to > > say much of anything. > > > > On Sunday, February 16, 2020, 8:11:17 AM MST, Bill J. Gray > > > wrote: > > > > > > On 2/16/20 1:20 AM, Sam Deen wrote: > > > I'm leaning on rock, personally. > > > > ? ? I expect to remain in the "insufficient data" camp for > > quite a while.? It's unlikely that we'll get enough > > astrometry to tell. > > > > > The current orbit gives an Area/mass ratio of 2.8 +/- 8.0 m^2/kg, > > which obviously is very far from conclusive, > > > > ? ? Extremely inconclusive.? The object could have the effectively > > zero AMR of a rock.? Or it could have the 5.6 m^2/kg of an empty > > trash bag object,? and the residuals would be the same.? Or > > anywhere in between and still fit the available data. > > > > ? ? We're up to 19 observations as I write this,? which has > > brought the AMR to 0.13 +/- 0.51. If it's artificial,? an > > AMR of,? say,? 0.02 would probably be in the right ballpark > > for a piece of junk this size.? I don't think it's an ETBO, > > because something that light would have a tough time staying > > in orbit around us;? solar radiation pressure would push > > it out into an heliocentric orbit... actually,? then into > > interstellar space;? ETBOs are that light. > > > > but seems to point towards the object not being artificial. For > > comparisons, here are a few AMRs according to Bill's distant artsat > > pseudo-mpec catalog: > > > > ? ? Yes,? but we also have,? for example,? ZTF00V9 = ZTF00Vv > > = ZTF00Y5 = ZTF00Yq,? with an area/mass ratio of 107 +/- 3 > > m^2/kg : > > > > https://www.projectpluto.com/pluto/mpecs/ztf00v9.htm#etbo > > > > ? ? and many in between.? I've learned,? mostly over the last > > couple of years,? that artsats come with a fairly bewildering > > range of area/mass ratios.? (I'd previously assumed such high > > AMRs must be bogus,? and that I had bad data or data for > > two or three different objects, or that it was maneuvering. > > Once I started looking for ETBOs, I realized they were > > everywhere.? One,? 'Multijunk', has been a "discovery" on > > NEOCP at least two dozen times.) > > > > > Im not sure how to use find_orb to force-fit test AMR values, > > > > ? ? You can apply a constraint of,? say,? "A=0.005",? much as > > you would constrain "e=1" if you thought it was a comet or > > "a=5.2,e=0" for a circular Jupiter Trojan orbit. > > > > ? but I suppose that even with a poorly-defined orbit, being able to > > demonstrate its AMR is over 0.05 m^2/kg would make it most likely not > > an artsat in my opinion at least. > > > > ? ? If you find,? say,? AMR = 0.020 +/- 0.001,? _then_ you've > > got evidence it's an artsat,? with the uncertainty in the > > value significantly less than the value itself.? Proving > > something is _not_ an artsat is a lot harder.? Tell me > > you've got AMR = 0.001 +/- 0.010, and I'll just say that > > an AMR of 0.01 would fit within that uncertainty,? so it > > _could_ be an artsat,? roughly as likely as being a rock. > > > > ? ? Getting an accurate AMR for a rock has happened... in > > fact,? for 2006 RH120 (only confirmed temporarily captured > > rock),? we got AMR = (98.5 +/- 2)E-5 m^2/kg.? That object, > > however,? did three orbits over most of a year,? and we got > > a radar observation on it.? Unless we get far more precovery > > data than I expect,? astrometry isn't going to tell us if > > this is a rock or not.? Radar data might -- for example, > > with 2018 AV2,? we not only measured a high AMR;? Arecibo > > got a stronger radar echo from it than would be expected > > for a rock.? Or spectroscopy,? as happened initially with > > J002E3 (it had the spectral signature of titanium dioxide > > paint).? Or infrared data;? if the albedo is near 100%, > > you start to think about an object with white TiO2 paint. > > > > > > > > Additionally, the aphelion of this thing is seriously impressively > > large. Its aphelion is recorded at 0.0148 +/- 0.0005 AU, which is > > larger than the radius of Earth's hill sphere at ~0.010004 AU. I > > assume find_orb wouldn't be giving a geocentric orbit if it was > > orbiting faster than escape velocity, though. > > > > ? ? It would,? but with e > 1. (In Settings,? you can > > choose the reference object.? The default 'automatic' > > setting gets you a geocentric orbit if the object is > > within the earth's sphere of influence,? a selenocentric > > orbit if it's with the moon's sphere of influence,? etc. > > But you can,? for example,? insist on a Neptune-centric > > orbit for an object that is nowhere near Neptune.) > > > > ? Running the orbit forwards shows it won't be staying in geocentric > > orbit for long, at least nominally. The radial velocity will reach its > > minimum around April 7, at which point I assume the gravitational hold > > of the sun will start to take over, and it will move back into > > heliocentric orbit. Running the orbit backwards nominally says it's > > been in orbit since February 13 2018, putting it as having orbited us > > for around 2 years by now. Of course, that's massively premature to > > conclude with only half a day's worth of observations. All I can say > > for sure is that it's orbiting us > > > right now, and was almost surely orbiting us since the November perigee. > > > > ? ? I think there may have been some previous perigees,? but > > yeah,? we don't have enough data yet to say. > > > > > > > > In regards to ephemerides: > > > > > > C26FED2 would have been above magnitude 23 since February 10, > > although with a low enough elongation that would have made detection > > improbable. The first time it really would have been detectable was on > > February 13 when it peaked around magnitude ~16-17 at an elongation of > > 124 degrees. It has been slowly dimming ever since, and will remain > > above magnitude 23 until February 26. > > > > > > I would give it good chances of at least a couple other > > observatories spotting it over the coming days. It's a shame the > > orbital period is so long, though. Once it stops being visible on > > February 26, it won't be coming back.. So, the next few days are all > > we have to figure out more about this weird object. Hopefully some > > larger scopes will get pointed at it in that time! > > > > > > ~Sam > > > On Saturday, February 15, 2020, 5:59:52 PM MST, Bill Gray > > >> wrote: > > > > > > > > >? ? ? With follow-up from (L01) Vi?njan,? it's confirmed that this > > > is a temporarily captured object.? Whether it's natural or junk > > > is unknown.? I _really_ hope someone gets more data for it.? If > > > it's a temporarily captured rock,? that's a Really Big Deal. > > > > > > -- Bill > > > > > > On 2/15/20 1:09 PM, Bill Gray wrote: > > >? > Hi folks, > > >? > > > >? >? ?? This object might just be a satellite.? If so,? it's a > > >? > somewhat unusual one, in a very elongated orbit.? It may be > > >? > lunar ejecta passing by us,? perhaps even a temporarily captured > > >? > object a la 2006 RH120 = 6R10DB9.? Or it could be heliocentric > > >? > junk passing by us, similar to J002E3 or 2018 AV2. Further > > >? > observations would be a really excellent idea. > > >? > > > >? > Thanks! -- Bill > > > > > > -- > > > neo_followup mailing list > > > neo_followup at projectpluto.com > > > > > >> > > > > > http://projectpluto.com/mailman/listinfo/neo_followup_projectpluto.com > > > > > > > > > > > > > -=-=-=-=-=-=-=-=-=-=-=- > Groups.io Links: You receive all messages sent to this group. > > View/Reply Online (#35370): https://groups.io/g/mpml/message/35370 > Mute This Topic: https://groups.io/mt/71319863/2027585 > -=-=- > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Posts to this list or information found within may be freely used, with the stipulation that MPML and the originating author are cited as the source of the information. > -=-=- > Group Owner: mpml+owner at groups.io > Unsubscribe: https://groups.io/g/mpml/unsub [planetaryscience at yahoo.com ] > > -=-=-=-=-=-=-=-=-=-=-=- > From pluto at projectpluto.com Wed Feb 19 12:20:07 2020 From: pluto at projectpluto.com (Bill Gray) Date: Wed, 19 Feb 2020 12:20:07 -0500 Subject: [neo_followup] {MPML} C26FED2 = interesting object In-Reply-To: References: <1c52e38e-1724-7150-47a2-d53b0df635b2@projectpluto.com> <1105329370.3618909.1581834014927@mail.yahoo.com> <1eed3d9c-b357-4360-fcae-731a2252d3c6@projectpluto.com> <15F3F2806A69F552.2600@groups.io> <15F4215553713F89.5373@groups.io> <1838777901.4764841.1582056841157@mail.yahoo.com> <41fe3fe8-34ef-836d-8018-fcd9d7c7894d@birtwhistle.org.uk> <1586394251.4891932.1582072587541@mail.yahoo.com> <6cd90ae5-061c-ac41-21e0-7472984e804c@projectpluto.com> Message-ID: <27b9074f-8714-3a13-1778-3da1ba1716fa@projectpluto.com> Hi Kacper, Thank you (and thanks also to MPC for reinstating this object.) At 40 observations, I'm getting AMR = -0.009 +/- 0.015 m^2/kg, still unable to distinguish rock from junk on that basis. (With variations depending on what outliers I toss. None of the observations are really all that bad, though.) If it's junk, it's not especially lightweight junk. At, say, AMR = 0.01 m^2/kg, and assuming it's a couple of square meters in cross-section (a rock-like albedo), it would mass a couple of hundred kilograms. Entirely possible, but we may be able to rule out at least some candidate bits of junk. -- Bill On 2/19/20 12:35 AM, Wierzchos, Kacper W - (kwierzchos) wrote: > Hi Bill, all, > The object is back on the NEOCP. We will target it tonight and in the next several nights weather permitting. > Kacper > > ----------------------------------------- > Kacper Wierzchos > Catalina Sky Survey > Lunar & Planetary Laboratory > University of Arizona > Tucson, Arizona 85721 > ----------------------------------------- > >> On Feb 18, 2020, at 8:09 PM, Bill J. Gray > wrote: >> >> Hi Sam, >> >> ??I'd second the request that observations be passed on. ?I, >> for one, ?have definitely not lost interest in this object. >> Far from it. >> >> ??MPC is quite possibly right about this object being junk. >> The nominal AMR I get, ?with 36 of 37 observations, ?is >> 0.014 +/- 0.021 m^2/kg, ?which really doesn't tell you if it's >> a rock or not. ?(It mostly just rules out it being, ?say, ?a loose >> scrap of insulation.) ?If it's a rock, ?we can run the orbit back >> a few orbits with some degree of confidence that the uncertainties >> reflect reality. ?If it's junk, ?we really have almost no idea >> where it was very far back. ?Junk does not (usually) fit the simple >> SRP model over those time spans. >> >> ??The answer will come from more data, ?and I do fear that that >> flow of data may cease now that MPC has dropped the object from >> NEOCP. ?We may have to follow this guy all the way down to V=24 >> to definitively get the AMR determined. ?(Though there will be some >> hope of getting precovery observations, ?especially if it's a rock.) >> >> ??I have an inquiry in to MPC about this, ?but haven't heard back >> yet. ?They do, ?I expect, ?have some access to information that I >> lack. ?Such as the ability to ask around NASA and ESA and JPL folks >> and say, ?"Do you know anything about this?". ?They may have done >> so and had someone reply, ?"Oh yeah, ?we know what that is." >> >> -- Bill >> >> On 2/18/20 7:36 PM, Sam Deen wrote: >>> Hi Peter, >>> Many thanks for the info. I had been assuming the uncertainties in all of the measurements, and probably in a handful of cases slightly underestimating them. To re-emphasize what I should have been clearer about in the original post: all of this is extremely preliminary, and prone to inaccuracy. I definitely wouldn't claim at this point that this object is certainly an artsat, it just seems to be generally leading towards being one. >>> That said, if anyone has further observations of this object over the next few days, please send them here, publicly or privately! I'd like to get to the bottom of this object if at all possible, and there's still many lingering questions that I don't believe have been adequately answered by the time the MPC pulled it from the NEOCP. >>> ~Sam >>> On Tuesday, February 18, 2020, 4:39:05 PM MST, Peter Birtwhistle > wrote: >>> Hi Sam, >>> At around mag +21 my four J95 positions are treated rather >>> optimistically in the standard FindOrb sigma.txt file. Setting their >>> Sigma's to 0.5" (which is still probably smaller than reality) and using >>> 36 of the 37 available observations, I get an AMR of 0.009 +/- 0.023 >>> m^2/kg, which looks to me like rock is still very possible. I'm a little >>> surprised it's already been pulled from the NEOCP as a "was not a minor >>> planet". >>> Peter >>> J95 >>> On 18/02/2020 20:14, Sam Deen via Groups.Io wrote: >>> > With the newest data, it's starting to look like C26FED2 might be an >>> > artsat, due to an interesting reason. >>> > >>> > I've been trying to peer past the March (now April) perigee for a >>> > while now, and something interesting has appeared with the most recent >>> > observations. >>> > >>> > Currently, the nominal perigee distance (including free SRP parameter) >>> > is 7200 +/- 5800 km. Furthermore, find_orb has started measuring the >>> > size/mass ratio with a significance of >1 sigma, at 0.031 +/- 0.021 >>> > m^2/kg. However, with the perigee distance constrained, the size/mass >>> > ratio becomes constrained as well. >>> > >>> > q=3800 (S22.91590 W84.36982) 0.023 +/- 0.015 m^2/kg >>> > q=4000 (S26.15681 W54.32953) 0.023 +/- 0.015 m^2/kg >>> > q=4200 (S29.53229 W167.13331) 0.024 +/- 0.014 m^2/kg >>> > q=4400 (S33.03794 E95.82559) 0.024 +/- 0.014 m^2/kg >>> > q=4600 (S36.68628 E9.64050) 0.025 +/- 0.014 m^2/kg >>> > q=4800 (S40.49965 W68.35291) 0.025 +/- 0.014 m^2/kg >>> > q=5000 (S44.51065 W139.79428) 0.026 +/- 0.014 m^2/kg >>> > q=5200 (S48.76527 E154.22276) 0.027 +/- 0.014 m^2/kg >>> > q=5400 (S53.33045 E93.06067) 0.027 +/- 0.014 m^2/kg >>> > q=5600 (S58.30737 E36.38756) 0.027 +/- 0.014 m^2/kg >>> > q=5800 (S63.86060 W15.62502) 0.028 +/- 0.014 m^2/kg >>> > q=6000 (S70.28076 W61.49060) 0.028 +/- 0.014 m^2/kg >>> > q=6200 (S78.02334 W92.00780) 0.029 +/- 0.014 m^2/kg >>> > q=6300 (S81.65253 W79.61484) 0.029 +/- 0.014 m^2/kg >>> > q=6350 (S80.24785 W46.75104) 0.029 +/- 0.014 m^2/kg >>> > q=6371 (S77.71472 W35.97998) 0.029 +/- 0.014 m^2/kg >>> > q=6400 0.029 +/- 0.014 m^2/kg >>> > q=6600 0.030 +/- 0.014 m^2/kg >>> > q=6800 0.030 +/- 0.014 m^2/kg >>> > q=7000 0.031 +/- 0.014 m^2/kg >>> > >>> > Obviously the area/mass ratio is a fairly poorly constrained even for >>> > objects observed over multiple months or years, but there seems to be >>> > something to be said about the fact that higher, more reasonable >>> > perigee solution it has, the more non-gravitational movement is >>> > required. It's erratic enough that I wouldn't be certain it's >>> > artificial at this point, but the fact that for it to be a rock, it >>> > would have to come awfully, nearly impossibly, close to Earth. >>> > >>> > At any rate, assuming nothing too funky happened around the April >>> > approach, now there's a few more certain orbits before April: >>> > >>> > 2019/04/04 q = 7200 +/- 5800 km, e = 0.9927 +/- 0.0057 >>> > 2019/01/18 q = 120,000 +/- 110,000 km, e = 0.885 +/- 0.079 >>> > 2018/10/25 q = 360,000 +/- 360,000 km, e = 0.65 +/- 0.30 (at which >>> > point it could have either entered Earth orbit, or been orbiting before.) >>> > >>> > ~Sam >>> > On Monday, February 17, 2020, 12:53:42 AM MST, Sam Deen via Groups.Io >>> > > wrote: >>> > >>> > >>> > Here's an update on the analysis with ~1.5 days of observations: >>> > >>> > Regarding the orbital evolution: >>> > >>> > The following perihelia have definitely, no-question taken place: >>> > >>> > 2019/03/23 (q = 4,300 +/- 7,600 km, e = 0.999 +/- 0.016) >>> > 2019/06/22 (q = 309,000 +/- 11,000 km, e = 0.632 +/- 0.017) >>> > 2019/09/03 (q = 341,000 +/- 24,000 km, e = 0.636 +/- 0.014) >>> > 2019/11/18 (q = 298,200 +/- 5,900 km, e = 0.7146 +/- 0.0073) >>> > 2020/02/13 (q = 47,061 +/- 22 km, e = 0.959661 +/- 0.000064) >>> > [ejected by April 2020] >>> > >>> > The object has definitely been orbiting us since the 2019/03/23 >>> > perigee at least, but unfortunately a close approach with the Moon >>> > between then and the next perigee combined with the resultant >>> > retroactive low perigee creates a gravitational keyhole that makes it >>> > really difficult to figure out what happened before. >>> > >>> > I very much doubt any of the orbits having it launching from Earth are >>> > true, since there's no way an object would be launched from the >>> > surface directly to a barely-bound orbit without any kind of reports >>> > on it. Not to mention that nothing above geosynchronous orbit was >>> > launched in March 2019. Beresheet was launched on 22 February to the >>> > Moon, but the projected orbit of this object doesn't really fit with a >>> > Feb 22 launch at all. I could analyze its possible "launch" path, but >>> > I expect it wouldn't be very helpful at all. >>> > >>> > Regarding the AMR and telling if it's an artsat or not: >>> > >>> > The AMR has been constrained to a somewhat nonsensical -0.016 +/- >>> > 0.067 m^2/kg (read: <0.051 m^2/kg) which rules out it being one of >>> > Bill's so-called ETBOs, but still leaves it firmly in the realm of >>> > possible artsat bits. Also, although the object has only been observed >>> > between elongations of ~128 and ~133 degrees, I suppose it's worth >>> > mentioning that it hasn't displayed any massive differences in >>> > brightness with phase or with time. The most consistent observer, L01, >>> > recorded its brightness as varying by only 0.2 magnitudes over the 5 >>> > observations made of it on 02/16 over 15 minutes, and 0.4 magnitudes >>> > over the 3 observations made of it on 02/17 over 20 minutes. Of course >>> > depending on the exact exposure length, this seems to imply that >>> > C26FED2 does not have a drastic, chaotic light curve like tumbling >>> > artsats tend to have. Just as a disclaimer, though, all of this is >>> > very preliminary and absolutely subject to being incorrect. >>> > >>> > Many thanks to all of the people who have gone to the effort of >>> > observing this object in recent days! Hopefully a handful more over >>> > the next few days should let us peer past the 2019/03/23 keyhole and >>> > see if it's been here a while, or just got captured. >>> > >>> > ~Sam >>> > On Sunday, February 16, 2020, 10:35:30 AM MST, Sam Deen via Groups.Io >>> > > wrote: >>> > >>> > >>> > My bad... noticed far too late that a large AMR makes an object empty >>> > trash baggy, and not more like a solid object. Ignore my comments on >>> > the current AMR estimate, they were definitely far too premature to >>> > say much of anything. >>> > >>> > On Sunday, February 16, 2020, 8:11:17 AM MST, Bill J. Gray >>> > > wrote: >>> > >>> > >>> > On 2/16/20 1:20 AM, Sam Deen wrote: >>> > > I'm leaning on rock, personally. >>> > >>> > ? ? I expect to remain in the "insufficient data" camp for >>> > quite a while.? It's unlikely that we'll get enough >>> > astrometry to tell. >>> > >>> > > The current orbit gives an Area/mass ratio of 2.8 +/- 8.0 m^2/kg, >>> > which obviously is very far from conclusive, >>> > >>> > ? ? Extremely inconclusive.? The object could have the effectively >>> > zero AMR of a rock.? Or it could have the 5.6 m^2/kg of an empty >>> > trash bag object,? and the residuals would be the same.? Or >>> > anywhere in between and still fit the available data. >>> > >>> > ? ? We're up to 19 observations as I write this,? which has >>> > brought the AMR to 0.13 +/- 0.51. If it's artificial,? an >>> > AMR of,? say,? 0.02 would probably be in the right ballpark >>> > for a piece of junk this size.? I don't think it's an ETBO, >>> > because something that light would have a tough time staying >>> > in orbit around us;? solar radiation pressure would push >>> > it out into an heliocentric orbit... actually,? then into >>> > interstellar space;? ETBOs are that light. >>> > >>> > but seems to point towards the object not being artificial. For >>> > comparisons, here are a few AMRs according to Bill's distant artsat >>> > pseudo-mpec catalog: >>> > >>> > ? ? Yes,? but we also have,? for example,? ZTF00V9 = ZTF00Vv >>> > = ZTF00Y5 = ZTF00Yq,? with an area/mass ratio of 107 +/- 3 >>> > m^2/kg : >>> > >>> >https://www.projectpluto.com/pluto/mpecs/ztf00v9.htm#etbo >>> > >>> > ? ? and many in between.? I've learned,? mostly over the last >>> > couple of years,? that artsats come with a fairly bewildering >>> > range of area/mass ratios.? (I'd previously assumed such high >>> > AMRs must be bogus,? and that I had bad data or data for >>> > two or three different objects, or that it was maneuvering. >>> > Once I started looking for ETBOs, I realized they were >>> > everywhere.? One,? 'Multijunk', has been a "discovery" on >>> > NEOCP at least two dozen times.) >>> > >>> > > Im not sure how to use find_orb to force-fit test AMR values, >>> > >>> > ? ? You can apply a constraint of,? say,? "A=0.005",? much as >>> > you would constrain "e=1" if you thought it was a comet or >>> > "a=5.2,e=0" for a circular Jupiter Trojan orbit. >>> > >>> > ? but I suppose that even with a poorly-defined orbit, being able to >>> > demonstrate its AMR is over 0.05 m^2/kg would make it most likely not >>> > an artsat in my opinion at least. >>> > >>> > ? ? If you find,? say,? AMR = 0.020 +/- 0.001,? _then_ you've >>> > got evidence it's an artsat,? with the uncertainty in the >>> > value significantly less than the value itself.? Proving >>> > something is _not_ an artsat is a lot harder.? Tell me >>> > you've got AMR = 0.001 +/- 0.010, and I'll just say that >>> > an AMR of 0.01 would fit within that uncertainty,? so it >>> > _could_ be an artsat,? roughly as likely as being a rock. >>> > >>> > ? ? Getting an accurate AMR for a rock has happened... in >>> > fact,? for 2006 RH120 (only confirmed temporarily captured >>> > rock),? we got AMR = (98.5 +/- 2)E-5 m^2/kg.? That object, >>> > however,? did three orbits over most of a year,? and we got >>> > a radar observation on it.? Unless we get far more precovery >>> > data than I expect,? astrometry isn't going to tell us if >>> > this is a rock or not.? Radar data might -- for example, >>> > with 2018 AV2,? we not only measured a high AMR;? Arecibo >>> > got a stronger radar echo from it than would be expected >>> > for a rock.? Or spectroscopy,? as happened initially with >>> > J002E3 (it had the spectral signature of titanium dioxide >>> > paint).? Or infrared data;? if the albedo is near 100%, >>> > you start to think about an object with white TiO2 paint. >>> > >>> > > >>> > > Additionally, the aphelion of this thing is seriously impressively >>> > large. Its aphelion is recorded at 0.0148 +/- 0.0005 AU, which is >>> > larger than the radius of Earth's hill sphere at ~0.010004 AU. I >>> > assume find_orb wouldn't be giving a geocentric orbit if it was >>> > orbiting faster than escape velocity, though. >>> > >>> > ? ? It would,? but with e > 1. (In Settings,? you can >>> > choose the reference object.? The default 'automatic' >>> > setting gets you a geocentric orbit if the object is >>> > within the earth's sphere of influence,? a selenocentric >>> > orbit if it's with the moon's sphere of influence,? etc. >>> > But you can,? for example,? insist on a Neptune-centric >>> > orbit for an object that is nowhere near Neptune.) >>> > >>> > ? Running the orbit forwards shows it won't be staying in geocentric >>> > orbit for long, at least nominally. The radial velocity will reach its >>> > minimum around April 7, at which point I assume the gravitational hold >>> > of the sun will start to take over, and it will move back into >>> > heliocentric orbit. Running the orbit backwards nominally says it's >>> > been in orbit since February 13 2018, putting it as having orbited us >>> > for around 2 years by now. Of course, that's massively premature to >>> > conclude with only half a day's worth of observations. All I can say >>> > for sure is that it's orbiting us >>> > > right now, and was almost surely orbiting us since the November perigee. >>> > >>> > ? ? I think there may have been some previous perigees,? but >>> > yeah,? we don't have enough data yet to say. >>> > >>> > > >>> > > In regards to ephemerides: >>> > > >>> > > C26FED2 would have been above magnitude 23 since February 10, >>> > although with a low enough elongation that would have made detection >>> > improbable. The first time it really would have been detectable was on >>> > February 13 when it peaked around magnitude ~16-17 at an elongation of >>> > 124 degrees. It has been slowly dimming ever since, and will remain >>> > above magnitude 23 until February 26. >>> > > >>> > > I would give it good chances of at least a couple other >>> > observatories spotting it over the coming days. It's a shame the >>> > orbital period is so long, though. Once it stops being visible on >>> > February 26, it won't be coming back.. So, the next few days are all >>> > we have to figure out more about this weird object. Hopefully some >>> > larger scopes will get pointed at it in that time! >>> > > >>> > > ~Sam >>> > > On Saturday, February 15, 2020, 5:59:52 PM MST, Bill Gray >>> > >> wrote: >>> > > >>> > > >>> > >? ? ? With follow-up from (L01) Vi?njan,? it's confirmed that this >>> > > is a temporarily captured object.? Whether it's natural or junk >>> > > is unknown.? I _really_ hope someone gets more data for it.? If >>> > > it's a temporarily captured rock,? that's a Really Big Deal. >>> > > >>> > > -- Bill >>> > > >>> > > On 2/15/20 1:09 PM, Bill Gray wrote: >>> > >? > Hi folks, >>> > >? > >>> > >? >? ?? This object might just be a satellite.? If so,? it's a >>> > >? > somewhat unusual one, in a very elongated orbit.? It may be >>> > >? > lunar ejecta passing by us,? perhaps even a temporarily captured >>> > >? > object a la 2006 RH120 = 6R10DB9.? Or it could be heliocentric >>> > >? > junk passing by us, similar to J002E3 or 2018 AV2. Further >>> > >? > observations would be a really excellent idea. >>> > >? > >>> > >? > Thanks! -- Bill >>> > > >>> > > -- >>> > > neo_followup mailing list >>> > >neo_followup at projectpluto.com > >>> > >>> > >> >>> > >>> > >http://projectpluto.com/mailman/listinfo/neo_followup_projectpluto.com >>> > >>> > >>> > >>> > >>> > >> > > _._,_._,_ > ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ > Groups.io Links: > > You receive all messages sent to this group. > > View/Reply Online (#35373) | Reply To Sender | Reply To Group | Mute This Topic | New Topic > > ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Posts to this list or information found within may be freely used, with the stipulation that MPML and the originating author are cited as the source of the information. > ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ > Your Subscription | Contact Group Owner | Unsubscribe [pluto at projectpluto.com] > _._,_._,_ From planet4589 at gmail.com Tue Feb 18 15:32:44 2020 From: planet4589 at gmail.com (Jonathan McDowell) Date: Tue, 18 Feb 2020 15:32:44 -0500 Subject: [neo_followup] {MPML} C26FED2 = interesting object In-Reply-To: <1838777901.4764841.1582056841157@mail.yahoo.com> References: <1c52e38e-1724-7150-47a2-d53b0df635b2@projectpluto.com> <1105329370.3618909.1581834014927@mail.yahoo.com> <1eed3d9c-b357-4360-fcae-731a2252d3c6@projectpluto.com> <15F3F2806A69F552.2600@groups.io> <15F4215553713F89.5373@groups.io> <1838777901.4764841.1582056841157@mail.yahoo.com> Message-ID: Interesting. 2018 Oct 25 would track with the BepiColombo launch, but all the objects from that should have had well above escape velocity. 2019 Apr 4 is the date of the Beresheet lunar orbit insertion - its perigee was 1700 km on Mar 31. Again, we don't expect that any objects fell off Beresheet at that time, but the coincidence in time is interesting. On Tue, 18 Feb 2020 at 15:14, Sam Deen via Groups.Io wrote: > With the newest data, it's starting to look like C26FED2 might be an > artsat, due to an interesting reason. > > I've been trying to peer past the March (now April) perigee for a while > now, and something interesting has appeared with the most recent > observations. > > Currently, the nominal perigee distance (including free SRP parameter) is > 7200 +/- 5800 km. Furthermore, find_orb has started measuring the size/mass > ratio with a significance of >1 sigma, at 0.031 +/- 0.021 m^2/kg. However, > with the perigee distance constrained, the size/mass ratio becomes > constrained as well. > > q=3800 (S22.91590 W84.36982) 0.023 +/- 0.015 m^2/kg > q=4000 (S26.15681 W54.32953) 0.023 +/- 0.015 m^2/kg > q=4200 (S29.53229 W167.13331) 0.024 +/- 0.014 m^2/kg > q=4400 (S33.03794 E95.82559) 0.024 +/- 0.014 m^2/kg > q=4600 (S36.68628 E9.64050) 0.025 +/- 0.014 m^2/kg > q=4800 (S40.49965 W68.35291) 0.025 +/- 0.014 m^2/kg > q=5000 (S44.51065 W139.79428) 0.026 +/- 0.014 m^2/kg > q=5200 (S48.76527 E154.22276) 0.027 +/- 0.014 m^2/kg > q=5400 (S53.33045 E93.06067) 0.027 +/- 0.014 m^2/kg > q=5600 (S58.30737 E36.38756) 0.027 +/- 0.014 m^2/kg > q=5800 (S63.86060 W15.62502) 0.028 +/- 0.014 m^2/kg > q=6000 (S70.28076 W61.49060) 0.028 +/- 0.014 m^2/kg > q=6200 (S78.02334 W92.00780) 0.029 +/- 0.014 m^2/kg > q=6300 (S81.65253 W79.61484) 0.029 +/- 0.014 m^2/kg > q=6350 (S80.24785 W46.75104) 0.029 +/- 0.014 m^2/kg > q=6371 (S77.71472 W35.97998) 0.029 +/- 0.014 m^2/kg > q=6400 0.029 +/- 0.014 m^2/kg > q=6600 0.030 +/- 0.014 m^2/kg > q=6800 0.030 +/- 0.014 m^2/kg > q=7000 0.031 +/- 0.014 m^2/kg > > Obviously the area/mass ratio is a fairly poorly constrained even for > objects observed over multiple months or years, but there seems to be > something to be said about the fact that higher, more reasonable perigee > solution it has, the more non-gravitational movement is required. It's > erratic enough that I wouldn't be certain it's artificial at this point, > but the fact that for it to be a rock, it would have to come awfully, > nearly impossibly, close to Earth. > > At any rate, assuming nothing too funky happened around the April > approach, now there's a few more certain orbits before April: > > 2019/04/04 q = 7200 +/- 5800 km, e = 0.9927 +/- 0.0057 > 2019/01/18 q = 120,000 +/- 110,000 km, e = 0.885 +/- 0.079 > 2018/10/25 q = 360,000 +/- 360,000 km, e = 0.65 +/- 0.30 (at which point > it could have either entered Earth orbit, or been orbiting before.) > > ~Sam > On Monday, February 17, 2020, 12:53:42 AM MST, Sam Deen via Groups.Io > wrote: > > > Here's an update on the analysis with ~1.5 days of observations: > > Regarding the orbital evolution: > > The following perihelia have definitely, no-question taken place: > > 2019/03/23 (q = 4,300 +/- 7,600 km, e = 0.999 +/- 0.016) > 2019/06/22 (q = 309,000 +/- 11,000 km, e = 0.632 +/- 0.017) > 2019/09/03 (q = 341,000 +/- 24,000 km, e = 0.636 +/- 0.014) > 2019/11/18 (q = 298,200 +/- 5,900 km, e = 0.7146 +/- 0.0073) > 2020/02/13 (q = 47,061 +/- 22 km, e = 0.959661 +/- 0.000064) > [ejected by April 2020] > > The object has definitely been orbiting us since the 2019/03/23 perigee at > least, but unfortunately a close approach with the Moon between then and > the next perigee combined with the resultant retroactive low perigee > creates a gravitational keyhole that makes it really difficult to figure > out what happened before. > > I very much doubt any of the orbits having it launching from Earth are > true, since there's no way an object would be launched from the surface > directly to a barely-bound orbit without any kind of reports on it. Not to > mention that nothing above geosynchronous orbit was launched in March 2019. > Beresheet was launched on 22 February to the Moon, but the projected orbit > of this object doesn't really fit with a Feb 22 launch at all. I could > analyze its possible "launch" path, but I expect it wouldn't be very > helpful at all. > > Regarding the AMR and telling if it's an artsat or not: > > The AMR has been constrained to a somewhat nonsensical -0.016 +/- 0.067 > m^2/kg (read: <0.051 m^2/kg) which rules out it being one of Bill's > so-called ETBOs, but still leaves it firmly in the realm of possible artsat > bits. Also, although the object has only been observed between elongations > of ~128 and ~133 degrees, I suppose it's worth mentioning that it hasn't > displayed any massive differences in brightness with phase or with time. > The most consistent observer, L01, recorded its brightness as varying by > only 0.2 magnitudes over the 5 observations made of it on 02/16 over 15 > minutes, and 0.4 magnitudes over the 3 observations made of it on 02/17 > over 20 minutes. Of course depending on the exact exposure length, this > seems to imply that C26FED2 does not have a drastic, chaotic light curve > like tumbling artsats tend to have. Just as a disclaimer, though, all of > this is very preliminary and absolutely subject to being incorrect. > > Many thanks to all of the people who have gone to the effort of observing > this object in recent days! Hopefully a handful more over the next few days > should let us peer past the 2019/03/23 keyhole and see if it's been here a > while, or just got captured. > > ~Sam > On Sunday, February 16, 2020, 10:35:30 AM MST, Sam Deen via Groups.Io > wrote: > > > My bad... noticed far too late that a large AMR makes an object empty > trash baggy, and not more like a solid object. Ignore my comments on the > current AMR estimate, they were definitely far too premature to say much of > anything. > > On Sunday, February 16, 2020, 8:11:17 AM MST, Bill J. Gray < > pluto at projectpluto.com> wrote: > > > On 2/16/20 1:20 AM, Sam Deen wrote: > > I'm leaning on rock, personally. > > I expect to remain in the "insufficient data" camp for > quite a while. It's unlikely that we'll get enough > astrometry to tell. > > > The current orbit gives an Area/mass ratio of 2.8 +/- 8.0 m^2/kg, which > obviously is very far from conclusive, > > Extremely inconclusive. The object could have the effectively > zero AMR of a rock. Or it could have the 5.6 m^2/kg of an empty > trash bag object, and the residuals would be the same. Or > anywhere in between and still fit the available data. > > We're up to 19 observations as I write this, which has > brought the AMR to 0.13 +/- 0.51. If it's artificial, an > AMR of, say, 0.02 would probably be in the right ballpark > for a piece of junk this size. I don't think it's an ETBO, > because something that light would have a tough time staying > in orbit around us; solar radiation pressure would push > it out into an heliocentric orbit... actually, then into > interstellar space; ETBOs are that light. > > but seems to point towards the object not being artificial. For > comparisons, here are a few AMRs according to Bill's distant artsat > pseudo-mpec catalog: > > Yes, but we also have, for example, ZTF00V9 = ZTF00Vv > = ZTF00Y5 = ZTF00Yq, with an area/mass ratio of 107 +/- 3 > m^2/kg : > > https://www.projectpluto.com/pluto/mpecs/ztf00v9.htm#etbo > > and many in between. I've learned, mostly over the last > couple of years, that artsats come with a fairly bewildering > range of area/mass ratios. (I'd previously assumed such high > AMRs must be bogus, and that I had bad data or data for > two or three different objects, or that it was maneuvering. > Once I started looking for ETBOs, I realized they were > everywhere. One, 'Multijunk', has been a "discovery" on > NEOCP at least two dozen times.) > > > Im not sure how to use find_orb to force-fit test AMR values, > > You can apply a constraint of, say, "A=0.005", much as > you would constrain "e=1" if you thought it was a comet or > "a=5.2,e=0" for a circular Jupiter Trojan orbit. > > but I suppose that even with a poorly-defined orbit, being able to > demonstrate its AMR is over 0.05 m^2/kg would make it most likely not an > artsat in my opinion at least. > > If you find, say, AMR = 0.020 +/- 0.001, _then_ you've > got evidence it's an artsat, with the uncertainty in the > value significantly less than the value itself. Proving > something is _not_ an artsat is a lot harder. Tell me > you've got AMR = 0.001 +/- 0.010, and I'll just say that > an AMR of 0.01 would fit within that uncertainty, so it > _could_ be an artsat, roughly as likely as being a rock. > > Getting an accurate AMR for a rock has happened... in > fact, for 2006 RH120 (only confirmed temporarily captured > rock), we got AMR = (98.5 +/- 2)E-5 m^2/kg. That object, > however, did three orbits over most of a year, and we got > a radar observation on it. Unless we get far more precovery > data than I expect, astrometry isn't going to tell us if > this is a rock or not. Radar data might -- for example, > with 2018 AV2, we not only measured a high AMR; Arecibo > got a stronger radar echo from it than would be expected > for a rock. Or spectroscopy, as happened initially with > J002E3 (it had the spectral signature of titanium dioxide > paint). Or infrared data; if the albedo is near 100%, > you start to think about an object with white TiO2 paint. > > > > > Additionally, the aphelion of this thing is seriously impressively > large. Its aphelion is recorded at 0.0148 +/- 0.0005 AU, which is larger > than the radius of Earth's hill sphere at ~0.010004 AU. I assume find_orb > wouldn't be giving a geocentric orbit if it was orbiting faster than escape > velocity, though. > > It would, but with e > 1. (In Settings, you can > choose the reference object. The default 'automatic' > setting gets you a geocentric orbit if the object is > within the earth's sphere of influence, a selenocentric > orbit if it's with the moon's sphere of influence, etc. > But you can, for example, insist on a Neptune-centric > orbit for an object that is nowhere near Neptune.) > > Running the orbit forwards shows it won't be staying in geocentric orbit > for long, at least nominally. The radial velocity will reach its minimum > around April 7, at which point I assume the gravitational hold of the sun > will start to take over, and it will move back into heliocentric orbit. > Running the orbit backwards nominally says it's been in orbit since > February 13 2018, putting it as having orbited us for around 2 years by > now. Of course, that's massively premature to conclude with only half a > day's worth of observations. All I can say for sure is that it's orbiting us > > right now, and was almost surely orbiting us since the November perigee. > > I think there may have been some previous perigees, but > yeah, we don't have enough data yet to say. > > > > > In regards to ephemerides: > > > > C26FED2 would have been above magnitude 23 since February 10, although > with a low enough elongation that would have made detection improbable. The > first time it really would have been detectable was on February 13 when it > peaked around magnitude ~16-17 at an elongation of 124 degrees. It has been > slowly dimming ever since, and will remain above magnitude 23 until > February 26. > > > > I would give it good chances of at least a couple other observatories > spotting it over the coming days. It's a shame the orbital period is so > long, though. Once it stops being visible on February 26, it won't be > coming back.. So, the next few days are all we have to figure out more > about this weird object. Hopefully some larger scopes will get pointed at > it in that time! > > > > ~Sam > > On Saturday, February 15, 2020, 5:59:52 PM MST, Bill Gray < > pluto at projectpluto.com> wrote: > > > > > > With follow-up from (L01) Vi?njan, it's confirmed that this > > is a temporarily captured object. Whether it's natural or junk > > is unknown. I _really_ hope someone gets more data for it. If > > it's a temporarily captured rock, that's a Really Big Deal. > > > > -- Bill > > > > On 2/15/20 1:09 PM, Bill Gray wrote: > > > Hi folks, > > > > > > This object might just be a satellite. If so, it's a > > > somewhat unusual one, in a very elongated orbit. It may be > > > lunar ejecta passing by us, perhaps even a temporarily captured > > > object a la 2006 RH120 = 6R10DB9. Or it could be heliocentric > > > junk passing by us, similar to J002E3 or 2018 AV2. Further > > > observations would be a really excellent idea. > > > > > > Thanks! -- Bill > > > > -- > > neo_followup mailing list > > neo_followup at projectpluto.com > > > http://projectpluto.com/mailman/listinfo/neo_followup_projectpluto.com > > > > > _._,_._,_ > ------------------------------ > Groups.io Links: > > You receive all messages sent to this group. > > View/Reply Online (#35366) | Reply > To Sender > > | Reply To Group > > | Mute This Topic | New Topic > > ------------------------------ > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Posts to this list or information found within may be freely used, with > the stipulation that MPML and the originating author are cited as the > source of the information. > ------------------------------ > Your Subscription | Contact > Group Owner | Unsubscribe > [planet4589 at gmail.com] > _._,_._,_ > > -------------- next part -------------- An HTML attachment was scrubbed... URL: From tony at gravitysimulator.com Tue Feb 18 17:31:51 2020 From: tony at gravitysimulator.com (Tony Dunn) Date: Tue, 18 Feb 2020 14:31:51 -0800 Subject: [neo_followup] {MPML} C26FED2 = interesting object In-Reply-To: References: <1c52e38e-1724-7150-47a2-d53b0df635b2@projectpluto.com> <1105329370.3618909.1581834014927@mail.yahoo.com> <1eed3d9c-b357-4360-fcae-731a2252d3c6@projectpluto.com> <15F3F2806A69F552.2600@groups.io> <15F4215553713F89.5373@groups.io> <1838777901.4764841.1582056841157@mail.yahoo.com> Message-ID: The object is not on NEOCP anymore. On Tue, Feb 18, 2020 at 1:25 PM Jonathan McDowell wrote: > Interesting. > 2018 Oct 25 would track with the BepiColombo launch, but all the objects > from that should have had well above escape velocity. > 2019 Apr 4 is the date of the Beresheet lunar orbit insertion - its > perigee was 1700 km on Mar 31. Again, we don't expect that any objects fell > off Beresheet > at that time, but the coincidence in time is interesting. > > On Tue, 18 Feb 2020 at 15:14, Sam Deen via Groups.Io yahoo.com at groups.io> wrote: > >> With the newest data, it's starting to look like C26FED2 might be an >> artsat, due to an interesting reason. >> >> I've been trying to peer past the March (now April) perigee for a while >> now, and something interesting has appeared with the most recent >> observations. >> >> Currently, the nominal perigee distance (including free SRP parameter) is >> 7200 +/- 5800 km. Furthermore, find_orb has started measuring the size/mass >> ratio with a significance of >1 sigma, at 0.031 +/- 0.021 m^2/kg. However, >> with the perigee distance constrained, the size/mass ratio becomes >> constrained as well. >> >> q=3800 (S22.91590 W84.36982) 0.023 +/- 0.015 m^2/kg >> q=4000 (S26.15681 W54.32953) 0.023 +/- 0.015 m^2/kg >> q=4200 (S29.53229 W167.13331) 0.024 +/- 0.014 m^2/kg >> q=4400 (S33.03794 E95.82559) 0.024 +/- 0.014 m^2/kg >> q=4600 (S36.68628 E9.64050) 0.025 +/- 0.014 m^2/kg >> q=4800 (S40.49965 W68.35291) 0.025 +/- 0.014 m^2/kg >> q=5000 (S44.51065 W139.79428) 0.026 +/- 0.014 m^2/kg >> q=5200 (S48.76527 E154.22276) 0.027 +/- 0.014 m^2/kg >> q=5400 (S53.33045 E93.06067) 0.027 +/- 0.014 m^2/kg >> q=5600 (S58.30737 E36.38756) 0.027 +/- 0.014 m^2/kg >> q=5800 (S63.86060 W15.62502) 0.028 +/- 0.014 m^2/kg >> q=6000 (S70.28076 W61.49060) 0.028 +/- 0.014 m^2/kg >> q=6200 (S78.02334 W92.00780) 0.029 +/- 0.014 m^2/kg >> q=6300 (S81.65253 W79.61484) 0.029 +/- 0.014 m^2/kg >> q=6350 (S80.24785 W46.75104) 0.029 +/- 0.014 m^2/kg >> q=6371 (S77.71472 W35.97998) 0.029 +/- 0.014 m^2/kg >> q=6400 0.029 +/- 0.014 m^2/kg >> q=6600 0.030 +/- 0.014 m^2/kg >> q=6800 0.030 +/- 0.014 m^2/kg >> q=7000 0.031 +/- 0.014 m^2/kg >> >> Obviously the area/mass ratio is a fairly poorly constrained even for >> objects observed over multiple months or years, but there seems to be >> something to be said about the fact that higher, more reasonable perigee >> solution it has, the more non-gravitational movement is required. It's >> erratic enough that I wouldn't be certain it's artificial at this point, >> but the fact that for it to be a rock, it would have to come awfully, >> nearly impossibly, close to Earth. >> >> At any rate, assuming nothing too funky happened around the April >> approach, now there's a few more certain orbits before April: >> >> 2019/04/04 q = 7200 +/- 5800 km, e = 0.9927 +/- 0.0057 >> 2019/01/18 q = 120,000 +/- 110,000 km, e = 0.885 +/- 0.079 >> 2018/10/25 q = 360,000 +/- 360,000 km, e = 0.65 +/- 0.30 (at which point >> it could have either entered Earth orbit, or been orbiting before.) >> >> ~Sam >> On Monday, February 17, 2020, 12:53:42 AM MST, Sam Deen via Groups.Io >> wrote: >> >> >> Here's an update on the analysis with ~1.5 days of observations: >> >> Regarding the orbital evolution: >> >> The following perihelia have definitely, no-question taken place: >> >> 2019/03/23 (q = 4,300 +/- 7,600 km, e = 0.999 +/- 0.016) >> 2019/06/22 (q = 309,000 +/- 11,000 km, e = 0.632 +/- 0.017) >> 2019/09/03 (q = 341,000 +/- 24,000 km, e = 0.636 +/- 0.014) >> 2019/11/18 (q = 298,200 +/- 5,900 km, e = 0.7146 +/- 0.0073) >> 2020/02/13 (q = 47,061 +/- 22 km, e = 0.959661 +/- 0.000064) >> [ejected by April 2020] >> >> The object has definitely been orbiting us since the 2019/03/23 perigee >> at least, but unfortunately a close approach with the Moon between then and >> the next perigee combined with the resultant retroactive low perigee >> creates a gravitational keyhole that makes it really difficult to figure >> out what happened before. >> >> I very much doubt any of the orbits having it launching from Earth are >> true, since there's no way an object would be launched from the surface >> directly to a barely-bound orbit without any kind of reports on it. Not to >> mention that nothing above geosynchronous orbit was launched in March 2019. >> Beresheet was launched on 22 February to the Moon, but the projected orbit >> of this object doesn't really fit with a Feb 22 launch at all. I could >> analyze its possible "launch" path, but I expect it wouldn't be very >> helpful at all. >> >> Regarding the AMR and telling if it's an artsat or not: >> >> The AMR has been constrained to a somewhat nonsensical -0.016 +/- 0.067 >> m^2/kg (read: <0.051 m^2/kg) which rules out it being one of Bill's >> so-called ETBOs, but still leaves it firmly in the realm of possible artsat >> bits. Also, although the object has only been observed between elongations >> of ~128 and ~133 degrees, I suppose it's worth mentioning that it hasn't >> displayed any massive differences in brightness with phase or with time. >> The most consistent observer, L01, recorded its brightness as varying by >> only 0.2 magnitudes over the 5 observations made of it on 02/16 over 15 >> minutes, and 0.4 magnitudes over the 3 observations made of it on 02/17 >> over 20 minutes. Of course depending on the exact exposure length, this >> seems to imply that C26FED2 does not have a drastic, chaotic light curve >> like tumbling artsats tend to have. Just as a disclaimer, though, all of >> this is very preliminary and absolutely subject to being incorrect. >> >> Many thanks to all of the people who have gone to the effort of observing >> this object in recent days! Hopefully a handful more over the next few days >> should let us peer past the 2019/03/23 keyhole and see if it's been here a >> while, or just got captured. >> >> ~Sam >> On Sunday, February 16, 2020, 10:35:30 AM MST, Sam Deen via Groups.Io >> wrote: >> >> >> My bad... noticed far too late that a large AMR makes an object empty >> trash baggy, and not more like a solid object. Ignore my comments on the >> current AMR estimate, they were definitely far too premature to say much of >> anything. >> >> On Sunday, February 16, 2020, 8:11:17 AM MST, Bill J. Gray < >> pluto at projectpluto.com> wrote: >> >> >> On 2/16/20 1:20 AM, Sam Deen wrote: >> > I'm leaning on rock, personally. >> >> I expect to remain in the "insufficient data" camp for >> quite a while. It's unlikely that we'll get enough >> astrometry to tell. >> >> > The current orbit gives an Area/mass ratio of 2.8 +/- 8.0 m^2/kg, which >> obviously is very far from conclusive, >> >> Extremely inconclusive. The object could have the effectively >> zero AMR of a rock. Or it could have the 5.6 m^2/kg of an empty >> trash bag object, and the residuals would be the same. Or >> anywhere in between and still fit the available data. >> >> We're up to 19 observations as I write this, which has >> brought the AMR to 0.13 +/- 0.51. If it's artificial, an >> AMR of, say, 0.02 would probably be in the right ballpark >> for a piece of junk this size. I don't think it's an ETBO, >> because something that light would have a tough time staying >> in orbit around us; solar radiation pressure would push >> it out into an heliocentric orbit... actually, then into >> interstellar space; ETBOs are that light. >> >> but seems to point towards the object not being artificial. For >> comparisons, here are a few AMRs according to Bill's distant artsat >> pseudo-mpec catalog: >> >> Yes, but we also have, for example, ZTF00V9 = ZTF00Vv >> = ZTF00Y5 = ZTF00Yq, with an area/mass ratio of 107 +/- 3 >> m^2/kg : >> >> https://www.projectpluto.com/pluto/mpecs/ztf00v9.htm#etbo >> >> and many in between. I've learned, mostly over the last >> couple of years, that artsats come with a fairly bewildering >> range of area/mass ratios. (I'd previously assumed such high >> AMRs must be bogus, and that I had bad data or data for >> two or three different objects, or that it was maneuvering. >> Once I started looking for ETBOs, I realized they were >> everywhere. One, 'Multijunk', has been a "discovery" on >> NEOCP at least two dozen times.) >> >> > Im not sure how to use find_orb to force-fit test AMR values, >> >> You can apply a constraint of, say, "A=0.005", much as >> you would constrain "e=1" if you thought it was a comet or >> "a=5.2,e=0" for a circular Jupiter Trojan orbit. >> >> but I suppose that even with a poorly-defined orbit, being able to >> demonstrate its AMR is over 0.05 m^2/kg would make it most likely not an >> artsat in my opinion at least. >> >> If you find, say, AMR = 0.020 +/- 0.001, _then_ you've >> got evidence it's an artsat, with the uncertainty in the >> value significantly less than the value itself. Proving >> something is _not_ an artsat is a lot harder. Tell me >> you've got AMR = 0.001 +/- 0.010, and I'll just say that >> an AMR of 0.01 would fit within that uncertainty, so it >> _could_ be an artsat, roughly as likely as being a rock. >> >> Getting an accurate AMR for a rock has happened... in >> fact, for 2006 RH120 (only confirmed temporarily captured >> rock), we got AMR = (98.5 +/- 2)E-5 m^2/kg. That object, >> however, did three orbits over most of a year, and we got >> a radar observation on it. Unless we get far more precovery >> data than I expect, astrometry isn't going to tell us if >> this is a rock or not. Radar data might -- for example, >> with 2018 AV2, we not only measured a high AMR; Arecibo >> got a stronger radar echo from it than would be expected >> for a rock. Or spectroscopy, as happened initially with >> J002E3 (it had the spectral signature of titanium dioxide >> paint). Or infrared data; if the albedo is near 100%, >> you start to think about an object with white TiO2 paint. >> >> > >> > Additionally, the aphelion of this thing is seriously impressively >> large. Its aphelion is recorded at 0.0148 +/- 0.0005 AU, which is larger >> than the radius of Earth's hill sphere at ~0.010004 AU. I assume find_orb >> wouldn't be giving a geocentric orbit if it was orbiting faster than escape >> velocity, though. >> >> It would, but with e > 1. (In Settings, you can >> choose the reference object. The default 'automatic' >> setting gets you a geocentric orbit if the object is >> within the earth's sphere of influence, a selenocentric >> orbit if it's with the moon's sphere of influence, etc. >> But you can, for example, insist on a Neptune-centric >> orbit for an object that is nowhere near Neptune.) >> >> Running the orbit forwards shows it won't be staying in geocentric >> orbit for long, at least nominally. The radial velocity will reach its >> minimum around April 7, at which point I assume the gravitational hold of >> the sun will start to take over, and it will move back into heliocentric >> orbit. Running the orbit backwards nominally says it's been in orbit since >> February 13 2018, putting it as having orbited us for around 2 years by >> now. Of course, that's massively premature to conclude with only half a >> day's worth of observations. All I can say for sure is that it's orbiting us >> > right now, and was almost surely orbiting us since the November perigee. >> >> I think there may have been some previous perigees, but >> yeah, we don't have enough data yet to say. >> >> > >> > In regards to ephemerides: >> > >> > C26FED2 would have been above magnitude 23 since February 10, although >> with a low enough elongation that would have made detection improbable. The >> first time it really would have been detectable was on February 13 when it >> peaked around magnitude ~16-17 at an elongation of 124 degrees. It has been >> slowly dimming ever since, and will remain above magnitude 23 until >> February 26. >> > >> > I would give it good chances of at least a couple other observatories >> spotting it over the coming days. It's a shame the orbital period is so >> long, though. Once it stops being visible on February 26, it won't be >> coming back.. So, the next few days are all we have to figure out more >> about this weird object. Hopefully some larger scopes will get pointed at >> it in that time! >> > >> > ~Sam >> > On Saturday, February 15, 2020, 5:59:52 PM MST, Bill Gray < >> pluto at projectpluto.com> wrote: >> > >> > >> > With follow-up from (L01) Vi?njan, it's confirmed that this >> > is a temporarily captured object. Whether it's natural or junk >> > is unknown. I _really_ hope someone gets more data for it. If >> > it's a temporarily captured rock, that's a Really Big Deal. >> > >> > -- Bill >> > >> > On 2/15/20 1:09 PM, Bill Gray wrote: >> > > Hi folks, >> > > >> > > This object might just be a satellite. If so, it's a >> > > somewhat unusual one, in a very elongated orbit. It may be >> > > lunar ejecta passing by us, perhaps even a temporarily captured >> > > object a la 2006 RH120 = 6R10DB9. Or it could be heliocentric >> > > junk passing by us, similar to J002E3 or 2018 AV2. Further >> > > observations would be a really excellent idea. >> > > >> > > Thanks! -- Bill >> > >> > -- >> > neo_followup mailing list >> > neo_followup at projectpluto.com >> >> > http://projectpluto.com/mailman/listinfo/neo_followup_projectpluto.com >> >> >> >> >> _._,_._,_ > ------------------------------ > Groups.io Links: > > You receive all messages sent to this group. > > View/Reply Online (#35367) | Reply > To Sender > > | Reply To Group > > | Mute This Topic | New Topic > > ------------------------------ > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > Posts to this list or information found within may be freely used, with > the stipulation that MPML and the originating author are cited as the > source of the information. > ------------------------------ > Your Subscription | Contact > Group Owner | Unsubscribe > [tony at gravitysimulator.com] > _._,_._,_ > > -------------- next part -------------- An HTML attachment was scrubbed... URL: From planetaryscience at yahoo.com Tue Feb 18 19:36:27 2020 From: planetaryscience at yahoo.com (Sam Deen) Date: Wed, 19 Feb 2020 00:36:27 +0000 (UTC) Subject: [neo_followup] {MPML} C26FED2 = interesting object In-Reply-To: <41fe3fe8-34ef-836d-8018-fcd9d7c7894d@birtwhistle.org.uk> References: <1c52e38e-1724-7150-47a2-d53b0df635b2@projectpluto.com> <1105329370.3618909.1581834014927@mail.yahoo.com> <1eed3d9c-b357-4360-fcae-731a2252d3c6@projectpluto.com> <15F3F2806A69F552.2600@groups.io> <15F4215553713F89.5373@groups.io> <1838777901.4764841.1582056841157@mail.yahoo.com> <41fe3fe8-34ef-836d-8018-fcd9d7c7894d@birtwhistle.org.uk> Message-ID: <1586394251.4891932.1582072587541@mail.yahoo.com> Hi Peter, Many thanks for the info. I had been assuming the uncertainties in all of the measurements, and probably in a handful of cases slightly underestimating them. To re-emphasize what I should have been clearer about in the original post: all of this is extremely preliminary, and prone to inaccuracy. I definitely wouldn't claim at this point that this object is certainly an artsat, it just seems to be generally leading towards being one. That said, if anyone has further observations of this object over the next few days, please send them here, publicly or privately! I'd like to get to the bottom of this object if at all possible, and there's still many lingering questions that I don't believe have been adequately answered by the time the MPC pulled it from the NEOCP. ~Sam On Tuesday, February 18, 2020, 4:39:05 PM MST, Peter Birtwhistle wrote: Hi Sam, At around mag +21 my four J95 positions are treated rather optimistically in the standard FindOrb sigma.txt file. Setting their Sigma's to 0.5" (which is still probably smaller than reality) and using 36 of the 37 available observations, I get an AMR of 0.009 +/- 0.023 m^2/kg, which looks to me like rock is still very possible. I'm a little surprised it's already been pulled from the NEOCP as a "was not a minor planet". Peter J95 On 18/02/2020 20:14, Sam Deen via Groups.Io wrote: > With the newest data, it's starting to look like C26FED2 might be an > artsat, due to an interesting reason. > > I've been trying to peer past the March (now April) perigee for a > while now, and something interesting has appeared with the most recent > observations. > > Currently, the nominal perigee distance (including free SRP parameter) > is 7200 +/- 5800 km. Furthermore, find_orb has started measuring the > size/mass ratio with a significance of >1 sigma, at 0.031 +/- 0.021 > m^2/kg. However, with the perigee distance constrained, the size/mass > ratio becomes constrained as well. > > q=3800 (S22.91590 W84.36982) 0.023 +/- 0.015 m^2/kg > q=4000 (S26.15681 W54.32953) 0.023 +/- 0.015 m^2/kg > q=4200 (S29.53229 W167.13331) 0.024 +/- 0.014 m^2/kg > q=4400 (S33.03794 E95.82559) 0.024 +/- 0.014 m^2/kg > q=4600 (S36.68628 E9.64050) 0.025 +/- 0.014 m^2/kg > q=4800 (S40.49965 W68.35291) 0.025 +/- 0.014 m^2/kg > q=5000 (S44.51065 W139.79428) 0.026 +/- 0.014 m^2/kg > q=5200 (S48.76527 E154.22276) 0.027 +/- 0.014 m^2/kg > q=5400 (S53.33045 E93.06067) 0.027 +/- 0.014 m^2/kg > q=5600 (S58.30737 E36.38756) 0.027 +/- 0.014 m^2/kg > q=5800 (S63.86060 W15.62502) 0.028 +/- 0.014 m^2/kg > q=6000 (S70.28076 W61.49060) 0.028 +/- 0.014 m^2/kg > q=6200 (S78.02334 W92.00780) 0.029 +/- 0.014 m^2/kg > q=6300 (S81.65253 W79.61484) 0.029 +/- 0.014 m^2/kg > q=6350 (S80.24785 W46.75104) 0.029 +/- 0.014 m^2/kg > q=6371 (S77.71472 W35.97998) 0.029 +/- 0.014 m^2/kg > q=6400 0.029 +/- 0.014 m^2/kg > q=6600 0.030 +/- 0.014 m^2/kg > q=6800 0.030 +/- 0.014 m^2/kg > q=7000 0.031 +/- 0.014 m^2/kg > > Obviously the area/mass ratio is a fairly poorly constrained even for > objects observed over multiple months or years, but there seems to be > something to be said about the fact that higher, more reasonable > perigee solution it has, the more non-gravitational movement is > required. It's erratic enough that I wouldn't be certain it's > artificial at this point, but the fact that for it to be a rock, it > would have to come awfully, nearly impossibly, close to Earth. > > At any rate, assuming nothing too funky happened around the April > approach, now there's a few more certain orbits before April: > > 2019/04/04 q = 7200 +/- 5800 km, e = 0.9927 +/- 0.0057 > 2019/01/18 q = 120,000 +/- 110,000 km, e = 0.885 +/- 0.079 > 2018/10/25 q = 360,000 +/- 360,000 km, e = 0.65 +/- 0.30 (at which > point it could have either entered Earth orbit, or been orbiting before.) > > ~Sam > On Monday, February 17, 2020, 12:53:42 AM MST, Sam Deen via Groups.Io > wrote: > > > Here's an update on the analysis with ~1.5 days of observations: > > Regarding the orbital evolution: > > The following perihelia have definitely, no-question taken place: > > 2019/03/23 (q = 4,300 +/- 7,600 km, e = 0.999 +/- 0.016) > 2019/06/22 (q = 309,000 +/- 11,000 km, e = 0.632 +/- 0.017) > 2019/09/03 (q = 341,000 +/- 24,000 km, e = 0.636 +/- 0.014) > 2019/11/18 (q = 298,200 +/- 5,900 km, e = 0.7146 +/- 0.0073) > 2020/02/13 (q = 47,061 +/- 22 km, e = 0.959661 +/- 0.000064) > [ejected by April 2020] > > The object has definitely been orbiting us since the 2019/03/23 > perigee at least, but unfortunately a close approach with the Moon > between then and the next perigee combined with the resultant > retroactive low perigee creates a gravitational keyhole that makes it > really difficult to figure out what happened before. > > I very much doubt any of the orbits having it launching from Earth are > true, since there's no way an object would be launched from the > surface directly to a barely-bound orbit without any kind of reports > on it. Not to mention that nothing above geosynchronous orbit was > launched in March 2019. Beresheet was launched on 22 February to the > Moon, but the projected orbit of this object doesn't really fit with a > Feb 22 launch at all. I could analyze its possible "launch" path, but > I expect it wouldn't be very helpful at all. > > Regarding the AMR and telling if it's an artsat or not: > > The AMR has been constrained to a somewhat nonsensical -0.016 +/- > 0.067 m^2/kg (read: <0.051 m^2/kg) which rules out it being one of > Bill's so-called ETBOs, but still leaves it firmly in the realm of > possible artsat bits. Also, although the object has only been observed > between elongations of ~128 and ~133 degrees, I suppose it's worth > mentioning that it hasn't displayed any massive differences in > brightness with phase or with time. The most consistent observer, L01, > recorded its brightness as varying by only 0.2 magnitudes over the 5 > observations made of it on 02/16 over 15 minutes, and 0.4 magnitudes > over the 3 observations made of it on 02/17 over 20 minutes. Of course > depending on the exact exposure length, this seems to imply that > C26FED2 does not have a drastic, chaotic light curve like tumbling > artsats tend to have. Just as a disclaimer, though, all of this is > very preliminary and absolutely subject to being incorrect. > > Many thanks to all of the people who have gone to the effort of > observing this object in recent days! Hopefully a handful more over > the next few days should let us peer past the 2019/03/23 keyhole and > see if it's been here a while, or just got captured. > > ~Sam > On Sunday, February 16, 2020, 10:35:30 AM MST, Sam Deen via Groups.Io > wrote: > > > My bad... noticed far too late that a large AMR makes an object empty > trash baggy, and not more like a solid object. Ignore my comments on > the current AMR estimate, they were definitely far too premature to > say much of anything. > > On Sunday, February 16, 2020, 8:11:17 AM MST, Bill J. Gray > wrote: > > > On 2/16/20 1:20 AM, Sam Deen wrote: > > I'm leaning on rock, personally. > > ? ? I expect to remain in the "insufficient data" camp for > quite a while.? It's unlikely that we'll get enough > astrometry to tell. > > > The current orbit gives an Area/mass ratio of 2.8 +/- 8.0 m^2/kg, > which obviously is very far from conclusive, > > ? ? Extremely inconclusive.? The object could have the effectively > zero AMR of a rock.? Or it could have the 5.6 m^2/kg of an empty > trash bag object,? and the residuals would be the same.? Or > anywhere in between and still fit the available data. > > ? ? We're up to 19 observations as I write this,? which has > brought the AMR to 0.13 +/- 0.51. If it's artificial,? an > AMR of,? say,? 0.02 would probably be in the right ballpark > for a piece of junk this size.? I don't think it's an ETBO, > because something that light would have a tough time staying > in orbit around us;? solar radiation pressure would push > it out into an heliocentric orbit... actually,? then into > interstellar space;? ETBOs are that light. > > but seems to point towards the object not being artificial. For > comparisons, here are a few AMRs according to Bill's distant artsat > pseudo-mpec catalog: > > ? ? Yes,? but we also have,? for example,? ZTF00V9 = ZTF00Vv > = ZTF00Y5 = ZTF00Yq,? with an area/mass ratio of 107 +/- 3 > m^2/kg : > > https://www.projectpluto.com/pluto/mpecs/ztf00v9.htm#etbo > > ? ? and many in between.? I've learned,? mostly over the last > couple of years,? that artsats come with a fairly bewildering > range of area/mass ratios.? (I'd previously assumed such high > AMRs must be bogus,? and that I had bad data or data for > two or three different objects, or that it was maneuvering. > Once I started looking for ETBOs, I realized they were > everywhere.? One,? 'Multijunk', has been a "discovery" on > NEOCP at least two dozen times.) > > > Im not sure how to use find_orb to force-fit test AMR values, > > ? ? You can apply a constraint of,? say,? "A=0.005",? much as > you would constrain "e=1" if you thought it was a comet or > "a=5.2,e=0" for a circular Jupiter Trojan orbit. > > ? but I suppose that even with a poorly-defined orbit, being able to > demonstrate its AMR is over 0.05 m^2/kg would make it most likely not > an artsat in my opinion at least. > > ? ? If you find,? say,? AMR = 0.020 +/- 0.001,? _then_ you've > got evidence it's an artsat,? with the uncertainty in the > value significantly less than the value itself.? Proving > something is _not_ an artsat is a lot harder.? Tell me > you've got AMR = 0.001 +/- 0.010, and I'll just say that > an AMR of 0.01 would fit within that uncertainty,? so it > _could_ be an artsat,? roughly as likely as being a rock. > > ? ? Getting an accurate AMR for a rock has happened... in > fact,? for 2006 RH120 (only confirmed temporarily captured > rock),? we got AMR = (98.5 +/- 2)E-5 m^2/kg.? That object, > however,? did three orbits over most of a year,? and we got > a radar observation on it.? Unless we get far more precovery > data than I expect,? astrometry isn't going to tell us if > this is a rock or not.? Radar data might -- for example, > with 2018 AV2,? we not only measured a high AMR;? Arecibo > got a stronger radar echo from it than would be expected > for a rock.? Or spectroscopy,? as happened initially with > J002E3 (it had the spectral signature of titanium dioxide > paint).? Or infrared data;? if the albedo is near 100%, > you start to think about an object with white TiO2 paint. > > > > > Additionally, the aphelion of this thing is seriously impressively > large. Its aphelion is recorded at 0.0148 +/- 0.0005 AU, which is > larger than the radius of Earth's hill sphere at ~0.010004 AU. I > assume find_orb wouldn't be giving a geocentric orbit if it was > orbiting faster than escape velocity, though. > > ? ? It would,? but with e > 1. (In Settings,? you can > choose the reference object.? The default 'automatic' > setting gets you a geocentric orbit if the object is > within the earth's sphere of influence,? a selenocentric > orbit if it's with the moon's sphere of influence,? etc. > But you can,? for example,? insist on a Neptune-centric > orbit for an object that is nowhere near Neptune.) > > ? Running the orbit forwards shows it won't be staying in geocentric > orbit for long, at least nominally. The radial velocity will reach its > minimum around April 7, at which point I assume the gravitational hold > of the sun will start to take over, and it will move back into > heliocentric orbit. Running the orbit backwards nominally says it's > been in orbit since February 13 2018, putting it as having orbited us > for around 2 years by now. Of course, that's massively premature to > conclude with only half a day's worth of observations. All I can say > for sure is that it's orbiting us > > right now, and was almost surely orbiting us since the November perigee. > > ? ? I think there may have been some previous perigees,? but > yeah,? we don't have enough data yet to say. > > > > > In regards to ephemerides: > > > > C26FED2 would have been above magnitude 23 since February 10, > although with a low enough elongation that would have made detection > improbable. The first time it really would have been detectable was on > February 13 when it peaked around magnitude ~16-17 at an elongation of > 124 degrees. It has been slowly dimming ever since, and will remain > above magnitude 23 until February 26. > > > > I would give it good chances of at least a couple other > observatories spotting it over the coming days. It's a shame the > orbital period is so long, though. Once it stops being visible on > February 26, it won't be coming back.. So, the next few days are all > we have to figure out more about this weird object. Hopefully some > larger scopes will get pointed at it in that time! > > > > ~Sam > > On Saturday, February 15, 2020, 5:59:52 PM MST, Bill Gray > > wrote: > > > > > >? ? ? With follow-up from (L01) Vi?njan,? it's confirmed that this > > is a temporarily captured object.? Whether it's natural or junk > > is unknown.? I _really_ hope someone gets more data for it.? If > > it's a temporarily captured rock,? that's a Really Big Deal. > > > > -- Bill > > > > On 2/15/20 1:09 PM, Bill Gray wrote: > >? > Hi folks, > >? > > >? >? ?? This object might just be a satellite.? If so,? it's a > >? > somewhat unusual one, in a very elongated orbit.? It may be > >? > lunar ejecta passing by us,? perhaps even a temporarily captured > >? > object a la 2006 RH120 = 6R10DB9.? Or it could be heliocentric > >? > junk passing by us, similar to J002E3 or 2018 AV2. Further > >? > observations would be a really excellent idea. > >? > > >? > Thanks! -- Bill > > > > -- > > neo_followup mailing list > > neo_followup at projectpluto.com > > > > > http://projectpluto.com/mailman/listinfo/neo_followup_projectpluto.com > > > > > -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#35370): https://groups.io/g/mpml/message/35370 Mute This Topic: https://groups.io/mt/71319863/2027585 -=-=- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Posts to this list or information found within may be freely used, with the stipulation that MPML and the originating author are cited as the source of the information. -=-=- Group Owner: mpml+owner at groups.io Unsubscribe: https://groups.io/g/mpml/unsub [planetaryscience at yahoo.com] -=-=-=-=-=-=-=-=-=-=-=- -------------- next part -------------- An HTML attachment was scrubbed... URL: From kwierzchos at email.arizona.edu Wed Feb 19 00:35:41 2020 From: kwierzchos at email.arizona.edu (Wierzchos, Kacper W - (kwierzchos)) Date: Wed, 19 Feb 2020 05:35:41 +0000 Subject: [neo_followup] {MPML} C26FED2 = interesting object In-Reply-To: <6cd90ae5-061c-ac41-21e0-7472984e804c@projectpluto.com> References: <1c52e38e-1724-7150-47a2-d53b0df635b2@projectpluto.com> <1105329370.3618909.1581834014927@mail.yahoo.com> <1eed3d9c-b357-4360-fcae-731a2252d3c6@projectpluto.com> <15F3F2806A69F552.2600@groups.io> <15F4215553713F89.5373@groups.io> <1838777901.4764841.1582056841157@mail.yahoo.com> <41fe3fe8-34ef-836d-8018-fcd9d7c7894d@birtwhistle.org.uk> <1586394251.4891932.1582072587541@mail.yahoo.com> <6cd90ae5-061c-ac41-21e0-7472984e804c@projectpluto.com> Message-ID: Hi Bill, all, The object is back on the NEOCP. We will target it tonight and in the next several nights weather permitting. Kacper ----------------------------------------- Kacper Wierzchos Catalina Sky Survey Lunar & Planetary Laboratory University of Arizona Tucson, Arizona 85721 ----------------------------------------- On Feb 18, 2020, at 8:09 PM, Bill J. Gray > wrote: Hi Sam, I'd second the request that observations be passed on. I, for one, have definitely not lost interest in this object. Far from it. MPC is quite possibly right about this object being junk. The nominal AMR I get, with 36 of 37 observations, is 0.014 +/- 0.021 m^2/kg, which really doesn't tell you if it's a rock or not. (It mostly just rules out it being, say, a loose scrap of insulation.) If it's a rock, we can run the orbit back a few orbits with some degree of confidence that the uncertainties reflect reality. If it's junk, we really have almost no idea where it was very far back. Junk does not (usually) fit the simple SRP model over those time spans. The answer will come from more data, and I do fear that that flow of data may cease now that MPC has dropped the object from NEOCP. We may have to follow this guy all the way down to V=24 to definitively get the AMR determined. (Though there will be some hope of getting precovery observations, especially if it's a rock.) I have an inquiry in to MPC about this, but haven't heard back yet. They do, I expect, have some access to information that I lack. Such as the ability to ask around NASA and ESA and JPL folks and say, "Do you know anything about this?". They may have done so and had someone reply, "Oh yeah, we know what that is." -- Bill On 2/18/20 7:36 PM, Sam Deen wrote: Hi Peter, Many thanks for the info. I had been assuming the uncertainties in all of the measurements, and probably in a handful of cases slightly underestimating them. To re-emphasize what I should have been clearer about in the original post: all of this is extremely preliminary, and prone to inaccuracy. I definitely wouldn't claim at this point that this object is certainly an artsat, it just seems to be generally leading towards being one. That said, if anyone has further observations of this object over the next few days, please send them here, publicly or privately! I'd like to get to the bottom of this object if at all possible, and there's still many lingering questions that I don't believe have been adequately answered by the time the MPC pulled it from the NEOCP. ~Sam On Tuesday, February 18, 2020, 4:39:05 PM MST, Peter Birtwhistle > wrote: Hi Sam, At around mag +21 my four J95 positions are treated rather optimistically in the standard FindOrb sigma.txt file. Setting their Sigma's to 0.5" (which is still probably smaller than reality) and using 36 of the 37 available observations, I get an AMR of 0.009 +/- 0.023 m^2/kg, which looks to me like rock is still very possible. I'm a little surprised it's already been pulled from the NEOCP as a "was not a minor planet". Peter J95 On 18/02/2020 20:14, Sam Deen via Groups.Io wrote: > With the newest data, it's starting to look like C26FED2 might be an > artsat, due to an interesting reason. > > I've been trying to peer past the March (now April) perigee for a > while now, and something interesting has appeared with the most recent > observations. > > Currently, the nominal perigee distance (including free SRP parameter) > is 7200 +/- 5800 km. Furthermore, find_orb has started measuring the > size/mass ratio with a significance of >1 sigma, at 0.031 +/- 0.021 > m^2/kg. However, with the perigee distance constrained, the size/mass > ratio becomes constrained as well. > > q=3800 (S22.91590 W84.36982) 0.023 +/- 0.015 m^2/kg > q=4000 (S26.15681 W54.32953) 0.023 +/- 0.015 m^2/kg > q=4200 (S29.53229 W167.13331) 0.024 +/- 0.014 m^2/kg > q=4400 (S33.03794 E95.82559) 0.024 +/- 0.014 m^2/kg > q=4600 (S36.68628 E9.64050) 0.025 +/- 0.014 m^2/kg > q=4800 (S40.49965 W68.35291) 0.025 +/- 0.014 m^2/kg > q=5000 (S44.51065 W139.79428) 0.026 +/- 0.014 m^2/kg > q=5200 (S48.76527 E154.22276) 0.027 +/- 0.014 m^2/kg > q=5400 (S53.33045 E93.06067) 0.027 +/- 0.014 m^2/kg > q=5600 (S58.30737 E36.38756) 0.027 +/- 0.014 m^2/kg > q=5800 (S63.86060 W15.62502) 0.028 +/- 0.014 m^2/kg > q=6000 (S70.28076 W61.49060) 0.028 +/- 0.014 m^2/kg > q=6200 (S78.02334 W92.00780) 0.029 +/- 0.014 m^2/kg > q=6300 (S81.65253 W79.61484) 0.029 +/- 0.014 m^2/kg > q=6350 (S80.24785 W46.75104) 0.029 +/- 0.014 m^2/kg > q=6371 (S77.71472 W35.97998) 0.029 +/- 0.014 m^2/kg > q=6400 0.029 +/- 0.014 m^2/kg > q=6600 0.030 +/- 0.014 m^2/kg > q=6800 0.030 +/- 0.014 m^2/kg > q=7000 0.031 +/- 0.014 m^2/kg > > Obviously the area/mass ratio is a fairly poorly constrained even for > objects observed over multiple months or years, but there seems to be > something to be said about the fact that higher, more reasonable > perigee solution it has, the more non-gravitational movement is > required. It's erratic enough that I wouldn't be certain it's > artificial at this point, but the fact that for it to be a rock, it > would have to come awfully, nearly impossibly, close to Earth. > > At any rate, assuming nothing too funky happened around the April > approach, now there's a few more certain orbits before April: > > 2019/04/04 q = 7200 +/- 5800 km, e = 0.9927 +/- 0.0057 > 2019/01/18 q = 120,000 +/- 110,000 km, e = 0.885 +/- 0.079 > 2018/10/25 q = 360,000 +/- 360,000 km, e = 0.65 +/- 0.30 (at which > point it could have either entered Earth orbit, or been orbiting before.) > > ~Sam > On Monday, February 17, 2020, 12:53:42 AM MST, Sam Deen via Groups.Io > > wrote: > > > Here's an update on the analysis with ~1.5 days of observations: > > Regarding the orbital evolution: > > The following perihelia have definitely, no-question taken place: > > 2019/03/23 (q = 4,300 +/- 7,600 km, e = 0.999 +/- 0.016) > 2019/06/22 (q = 309,000 +/- 11,000 km, e = 0.632 +/- 0.017) > 2019/09/03 (q = 341,000 +/- 24,000 km, e = 0.636 +/- 0.014) > 2019/11/18 (q = 298,200 +/- 5,900 km, e = 0.7146 +/- 0.0073) > 2020/02/13 (q = 47,061 +/- 22 km, e = 0.959661 +/- 0.000064) > [ejected by April 2020] > > The object has definitely been orbiting us since the 2019/03/23 > perigee at least, but unfortunately a close approach with the Moon > between then and the next perigee combined with the resultant > retroactive low perigee creates a gravitational keyhole that makes it > really difficult to figure out what happened before. > > I very much doubt any of the orbits having it launching from Earth are > true, since there's no way an object would be launched from the > surface directly to a barely-bound orbit without any kind of reports > on it. Not to mention that nothing above geosynchronous orbit was > launched in March 2019. Beresheet was launched on 22 February to the > Moon, but the projected orbit of this object doesn't really fit with a > Feb 22 launch at all. I could analyze its possible "launch" path, but > I expect it wouldn't be very helpful at all. > > Regarding the AMR and telling if it's an artsat or not: > > The AMR has been constrained to a somewhat nonsensical -0.016 +/- > 0.067 m^2/kg (read: <0.051 m^2/kg) which rules out it being one of > Bill's so-called ETBOs, but still leaves it firmly in the realm of > possible artsat bits. Also, although the object has only been observed > between elongations of ~128 and ~133 degrees, I suppose it's worth > mentioning that it hasn't displayed any massive differences in > brightness with phase or with time. The most consistent observer, L01, > recorded its brightness as varying by only 0.2 magnitudes over the 5 > observations made of it on 02/16 over 15 minutes, and 0.4 magnitudes > over the 3 observations made of it on 02/17 over 20 minutes. Of course > depending on the exact exposure length, this seems to imply that > C26FED2 does not have a drastic, chaotic light curve like tumbling > artsats tend to have. Just as a disclaimer, though, all of this is > very preliminary and absolutely subject to being incorrect. > > Many thanks to all of the people who have gone to the effort of > observing this object in recent days! Hopefully a handful more over > the next few days should let us peer past the 2019/03/23 keyhole and > see if it's been here a while, or just got captured. > > ~Sam > On Sunday, February 16, 2020, 10:35:30 AM MST, Sam Deen via Groups.Io > > wrote: > > > My bad... noticed far too late that a large AMR makes an object empty > trash baggy, and not more like a solid object. Ignore my comments on > the current AMR estimate, they were definitely far too premature to > say much of anything. > > On Sunday, February 16, 2020, 8:11:17 AM MST, Bill J. Gray > > wrote: > > > On 2/16/20 1:20 AM, Sam Deen wrote: > > I'm leaning on rock, personally. > > I expect to remain in the "insufficient data" camp for > quite a while. It's unlikely that we'll get enough > astrometry to tell. > > > The current orbit gives an Area/mass ratio of 2.8 +/- 8.0 m^2/kg, > which obviously is very far from conclusive, > > Extremely inconclusive. The object could have the effectively > zero AMR of a rock. Or it could have the 5.6 m^2/kg of an empty > trash bag object, and the residuals would be the same. Or > anywhere in between and still fit the available data. > > We're up to 19 observations as I write this, which has > brought the AMR to 0.13 +/- 0.51. If it's artificial, an > AMR of, say, 0.02 would probably be in the right ballpark > for a piece of junk this size. I don't think it's an ETBO, > because something that light would have a tough time staying > in orbit around us; solar radiation pressure would push > it out into an heliocentric orbit... actually, then into > interstellar space; ETBOs are that light. > > but seems to point towards the object not being artificial. For > comparisons, here are a few AMRs according to Bill's distant artsat > pseudo-mpec catalog: > > Yes, but we also have, for example, ZTF00V9 = ZTF00Vv > = ZTF00Y5 = ZTF00Yq, with an area/mass ratio of 107 +/- 3 > m^2/kg : > > https://www.projectpluto.com/pluto/mpecs/ztf00v9.htm#etbo > > and many in between. I've learned, mostly over the last > couple of years, that artsats come with a fairly bewildering > range of area/mass ratios. (I'd previously assumed such high > AMRs must be bogus, and that I had bad data or data for > two or three different objects, or that it was maneuvering. > Once I started looking for ETBOs, I realized they were > everywhere. One, 'Multijunk', has been a "discovery" on > NEOCP at least two dozen times.) > > > Im not sure how to use find_orb to force-fit test AMR values, > > You can apply a constraint of, say, "A=0.005", much as > you would constrain "e=1" if you thought it was a comet or > "a=5.2,e=0" for a circular Jupiter Trojan orbit. > > but I suppose that even with a poorly-defined orbit, being able to > demonstrate its AMR is over 0.05 m^2/kg would make it most likely not > an artsat in my opinion at least. > > If you find, say, AMR = 0.020 +/- 0.001, _then_ you've > got evidence it's an artsat, with the uncertainty in the > value significantly less than the value itself. Proving > something is _not_ an artsat is a lot harder. Tell me > you've got AMR = 0.001 +/- 0.010, and I'll just say that > an AMR of 0.01 would fit within that uncertainty, so it > _could_ be an artsat, roughly as likely as being a rock. > > Getting an accurate AMR for a rock has happened... in > fact, for 2006 RH120 (only confirmed temporarily captured > rock), we got AMR = (98.5 +/- 2)E-5 m^2/kg. That object, > however, did three orbits over most of a year, and we got > a radar observation on it. Unless we get far more precovery > data than I expect, astrometry isn't going to tell us if > this is a rock or not. Radar data might -- for example, > with 2018 AV2, we not only measured a high AMR; Arecibo > got a stronger radar echo from it than would be expected > for a rock. Or spectroscopy, as happened initially with > J002E3 (it had the spectral signature of titanium dioxide > paint). Or infrared data; if the albedo is near 100%, > you start to think about an object with white TiO2 paint. > > > > > Additionally, the aphelion of this thing is seriously impressively > large. Its aphelion is recorded at 0.0148 +/- 0.0005 AU, which is > larger than the radius of Earth's hill sphere at ~0.010004 AU. I > assume find_orb wouldn't be giving a geocentric orbit if it was > orbiting faster than escape velocity, though. > > It would, but with e > 1. (In Settings, you can > choose the reference object. The default 'automatic' > setting gets you a geocentric orbit if the object is > within the earth's sphere of influence, a selenocentric > orbit if it's with the moon's sphere of influence, etc. > But you can, for example, insist on a Neptune-centric > orbit for an object that is nowhere near Neptune.) > > Running the orbit forwards shows it won't be staying in geocentric > orbit for long, at least nominally. The radial velocity will reach its > minimum around April 7, at which point I assume the gravitational hold > of the sun will start to take over, and it will move back into > heliocentric orbit. Running the orbit backwards nominally says it's > been in orbit since February 13 2018, putting it as having orbited us > for around 2 years by now. Of course, that's massively premature to > conclude with only half a day's worth of observations. All I can say > for sure is that it's orbiting us > > right now, and was almost surely orbiting us since the November perigee. > > I think there may have been some previous perigees, but > yeah, we don't have enough data yet to say. > > > > > In regards to ephemerides: > > > > C26FED2 would have been above magnitude 23 since February 10, > although with a low enough elongation that would have made detection > improbable. The first time it really would have been detectable was on > February 13 when it peaked around magnitude ~16-17 at an elongation of > 124 degrees. It has been slowly dimming ever since, and will remain > above magnitude 23 until February 26. > > > > I would give it good chances of at least a couple other > observatories spotting it over the coming days. It's a shame the > orbital period is so long, though. Once it stops being visible on > February 26, it won't be coming back.. So, the next few days are all > we have to figure out more about this weird object. Hopefully some > larger scopes will get pointed at it in that time! > > > > ~Sam > > On Saturday, February 15, 2020, 5:59:52 PM MST, Bill Gray > >> wrote: > > > > > > With follow-up from (L01) Vi?njan, it's confirmed that this > > is a temporarily captured object. Whether it's natural or junk > > is unknown. I _really_ hope someone gets more data for it. If > > it's a temporarily captured rock, that's a Really Big Deal. > > > > -- Bill > > > > On 2/15/20 1:09 PM, Bill Gray wrote: > > > Hi folks, > > > > > > This object might just be a satellite. If so, it's a > > > somewhat unusual one, in a very elongated orbit. It may be > > > lunar ejecta passing by us, perhaps even a temporarily captured > > > object a la 2006 RH120 = 6R10DB9. Or it could be heliocentric > > > junk passing by us, similar to J002E3 or 2018 AV2. Further > > > observations would be a really excellent idea. > > > > > > Thanks! -- Bill > > > > -- > > neo_followup mailing list > > neo_followup at projectpluto.com > > > >> > > > http://projectpluto.com/mailman/listinfo/neo_followup_projectpluto.com > > > > > -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. 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