[neo_followup] A10i6zC = geocentric transfer debris, probably related to ztf01nf

[Bill Gray]

Hi Sam,  all,

On 11/23/19 12:37 PM, Sam Deen wrote:
> the object A10i6zC on the NEOCP is pretty obviously an artsat:

    Yup,  kinda puzzling that it's still on NEOCP.  I assume
MPC will remove it soon as "not a minor planet".

   I ran the object through Sat_ID,  of course,  though without
any success in matching it to a known object that way.

>     Perigee 2019 Nov 20.909404 +/- 0.0275 TT = 21:49:32 (JD 2458808.409404)
> Epoch 2019 Nov 21.0 TT = JDT 2458808.5                        AutoNEOCP
> M  33.13518455 +/- 8                (J2000 equator)
> n 365.74775320 +/- 15.3             Peri.  193.14340 +/- 0.7
> a 41797.3801 +/- 1165               Node    41.26207 +/- 0.21
> e   0.6862850 +/- 0.0149            Incl.   32.72596 +/- 0.15
> P1417.34m/0.984dH  <https://www.minorplanetcenter.net/iau/lists/Sizes.html>  32.7   G  0.15   U 14.6
> q 13112.4616 +/- 1008    Q 70482.2986 +/- 1379
>  From 5 observations 2019 Nov. 21 (46.9 min); mean residual 0".16
> 
> and based on the orbit, I figured I'd check if it was any one of the many geocentric transfer debris we know of. The best fit I could find was ztf01nf, discovered around this time last year:

    You may be on to something there.  It is _very_ difficult
to say,  though.  If this is an "empty trash bag object",  its
current orbit would be a somewhat scrambled version of what it
was a year ago.  There is,  for example,  no real chance of
linking the two (unless,  _maybe_,  more data comes up.)

    However,  as an ETBO,  the change in eccentricity would be
easy to explain.  ETBOs tend to change quickly in inclination
and eccentricity.  (Which can make it nearly impossible to link
apparition A to apparition B,  unless the two apparitions are
closely spaced enough that the orbits still look vaguely similar.)
But it's hard for solar radiation pressure to add to or subtract
from the total energy,  i.e.,  the semimajor axis.  It seems that
anything it gains on half the orbit (withthe sun "at its back"),
it loses on the other half of the orbit ("going into a headwind").

-- Bill

> www.projectpluto.com/pluto/mpecs/ztf01nf.htm <http://www.projectpluto.com/pluto/mpecs/ztf01nf.htm>
> 
>     Perigee 2018 Nov 14.679965 +/- 0.00239 TT = 16:19:09 (JD 2458437.179965)
> Epoch 2018 Nov 15.0 TT = JDT 2458437.5                        Gray
> M 120.40721599 +/- 0.58             (J2000 equator)
> n 376.23157195 +/- 1                Peri.  200.98066 +/- 0.06
> a 41017.2633 +/- 72.9               Node    37.37637 +/- 0.0018
> e   0.7805021 +/- 0.000384          Incl.   32.97280 +/- 0.0054
> P1377.85m/0.957dH  <https://www.minorplanetcenter.net/iau/lists/Sizes.html>  34.4   G  0.15   U 12.7
> q 9003.20195 +/- 28.5    Q 73031.3248 +/- 121
>  From 6 observations 2018 Nov. 15 (3.2 hr); mean residual 0".417
> 
> the main problem with the linkage is that the eccentricity seems to have inexplicably decreased while keeping the semimajor axis roughly the same. Otherwise, the linkage seems pretty solid.
> 
> ~Sam
>