From pluto at projectpluto.com  Sat Nov 14 13:31:04 2020
From: pluto at projectpluto.com (Bill Gray)
Date: Sat, 14 Nov 2020 13:31:04 -0500
Subject: [neo_followup] A10sHcN = really close, but missed
Message-ID: <7e117491-9856-64ea-059f-e05a103a6585@projectpluto.com>

Hello all,

    ATLAS got this object last night,  already on its way back
to interplanetary space,  with an orbit that showed it had
missed us by at most a couple of thousand kilometers.  With
follow-up from (Q70) Glenlee Observatory in Queensland,
Australia,  and a couple of detections dug out from (I41)
ZTF data,  we have q=6752 +/- 13 km :

https://www.projectpluto.com/xfer/a10shcn.htm

    At its closest,  at 17:19 UTC,  the object was about
373 km over French Polynesia.  The flyby changed its orbit
from one roughly between Earth and Mars (q=0.99 AU,
Q=1.64 AU) to one roughly between Earth and Venus
(q=0.723 AU,  Q=1.092 AU).  Hope its inhabitants like
warm weather.

    I briefly thought this might be a newly-launched
interplanetary artsat.  When they're launched,  they usually
have perigees just outside the earth's atmosphere,  and this
is a perfect match for that.  However,  this object would
have been launched retrograde (relative to the earth),  at
an inclination of about 128 degrees.  That would be a huge
waste of fuel and,  as far as I know,  has never actually
happened.

    It's currently down around mag 19,  and still on NEOCP.
I assume we'll see some more data come in for it over the
next day or so.

-- Bill



From tony at gravitysimulator.com  Sat Nov 14 14:53:39 2020
From: tony at gravitysimulator.com (Tony Dunn)
Date: Sat, 14 Nov 2020 11:53:39 -0800
Subject: [neo_followup] {MPML} A10sHcN = really close, but missed
In-Reply-To: <7e117491-9856-64ea-059f-e05a103a6585@projectpluto.com>
References: <7e117491-9856-64ea-059f-e05a103a6585@projectpluto.com>
Message-ID: <CABd4VbSkbBUz_Eohps-T4a-smayrD_V-VyZ9n2e5SeV9RvhM4A@mail.gmail.com>

Here's a few animations.
https://twitter.com/tony873004/status/1327699921462386688

On Sat, Nov 14, 2020 at 10:31 AM Bill J. Gray <pluto at projectpluto.com>
wrote:

> Hello all,
>
>     ATLAS got this object last night,  already on its way back
> to interplanetary space,  with an orbit that showed it had
> missed us by at most a couple of thousand kilometers.  With
> follow-up from (Q70) Glenlee Observatory in Queensland,
> Australia,  and a couple of detections dug out from (I41)
> ZTF data,  we have q=6752 +/- 13 km :
>
> https://www.projectpluto.com/xfer/a10shcn.htm
>
>     At its closest,  at 17:19 UTC,  the object was about
> 373 km over French Polynesia.  The flyby changed its orbit
> from one roughly between Earth and Mars (q=0.99 AU,
> Q=1.64 AU) to one roughly between Earth and Venus
> (q=0.723 AU,  Q=1.092 AU).  Hope its inhabitants like
> warm weather.
>
>     I briefly thought this might be a newly-launched
> interplanetary artsat.  When they're launched,  they usually
> have perigees just outside the earth's atmosphere,  and this
> is a perfect match for that.  However,  this object would
> have been launched retrograde (relative to the earth),  at
> an inclination of about 128 degrees.  That would be a huge
> waste of fuel and,  as far as I know,  has never actually
> happened.
>
>     It's currently down around mag 19,  and still on NEOCP.
> I assume we'll see some more data come in for it over the
> next day or so.
>
> -- Bill
>
>
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From planetaryscience at yahoo.com  Sun Nov 15 14:44:33 2020
From: planetaryscience at yahoo.com (Sam Deen)
Date: Sun, 15 Nov 2020 19:44:33 +0000 (UTC)
Subject: [neo_followup] C3X8FH2, likely fragment of 2014 WJ6,
 whizzes by Earth
References: <1960110700.5745250.1605469473601.ref@mail.yahoo.com>
Message-ID: <1960110700.5745250.1605469473601@mail.yahoo.com>

Hi all,

A pretty interesting TJ<3 looking object was added to the NEOCP earlier today, found by MLS with a 2 hour observation arc. Ultimately any orbit with an arc measured in hours is going to not be very robust, but this one passed close enough to us (58,000 +/- 10,000 km) that you can get a decent enough idea of it. Nominally it's this:

   Perihelion 2020 Oct 10.698938 +/- 1.61 TT = 16:46:28 (JD 2459133.198938)
Epoch 2020 Nov 15.0 TT = JDT 2459168.5   Earth MOID: 0.0000   Ju: 0.6612
M   6.80577660 +/- 4.6              (J2000 ecliptic)          Find_Orb
n   0.19279240 +/- 0.133            Peri.  126.60087 +/- 0.6
a   2.96762782 +/- 1.37             Node   232.43714 +/- 0.047
e   0.7231549 +/- 0.133             Incl.    6.23886 +/- 0.8
P   5.11                   H 31.2   G  0.15   U 11.4  
q 0.82157312 +/- 0.021    Q 5.11368252 +/- 3.58
>From 7 observations 2020 Nov. 15 (1.9 hr); mean residual 0".37

Which puts it as a surprisingly small jupiter-crossing asteroid. In fact, if the nominal orbit is true, it would be the only H>30 object ever discovered with an aphelion beyond 5 AU. The chances of recovery aren't too big at the moment though- because of its small size and understandably high velocity, it's already at magnitude 22-23 with an uncertainty of several arcminutes, so unless someone somehow manages to snap the CFHT around on it tonight, this seems to be all the data we're going to get.

Fortunately, I don't think we need a lot more data. Out of curiosity, I performed a search of other asteroids on similar orbits and turned up a surprisingly robust match: 2014 WJ6, an H=27.1 asteroid on a similar enough orbit that I feel confident suggesting that C3X8FH2 is a tiny fragment of it, maybe even a divorced binary- even with the uncertainty in its exact eccentricity.

https://i.imgur.com/zzC5F8S.png

I wonder if there are any other associated asteroids with sizes this small...

~Sam



From pluto at projectpluto.com  Sun Nov 29 12:52:54 2020
From: pluto at projectpluto.com (Bill Gray)
Date: Sun, 29 Nov 2020 12:52:54 -0500
Subject: [neo_followup] 2020 SO observations?
Message-ID: <f4279c97-93c7-18b4-b984-defcd1c8ec16@projectpluto.com>

Hi folks,

    This is actually junk,  the Centaur stage from the Surveyor
2 mission in 1966.

    Apparently,  radar observations are planned for this object.
You'd think (well,  _I_ at least thought) that the current
astrometry would define the orbit nicely.  However,  we're at
the point where you can't fit the orbit well without including
additional non-gravitational forces,  and it's close in (meaning
faster apparent motion and more along-track ephemeris error),
_and_ it's somewhat close to the moon (about nine degrees right
now),  so we aren't getting routine survey data.  As a result,
the ephemeris uncertainty is already several arcseconds.

    All of which is a long-winded way of saying that it'd be a
good idea to get some astrometry on this object,  and/or a
light curve or rotation period (it's getting quite bright...
at mag 17.2 as I write this,  but that's because it's
emerging from the earth's shadow;  it'll be back up to 15.4
in an hour or so.)

    The rotation period is a useful bit of info for radar
observation planning.  The faster it rotates,  the more the
returned signal is "spread out" in frequency,  and it can
help to know that ahead of time.

    Usual comments about the need to be _really_ careful about
timing;  a one-second timing error now would correspond to
roughly a two-arcsecond measurement error,  i.e.,  huge.
We could still use your data,  but only partly ("the object
passed this point",  instead of "the object passed this point
at this time".)

-- Bill