[neo_followup] Tianwen-1 astrometry/ephemerides

[Bill Gray]

Hi folks,

    I've received astrometry for a Tianwen-1 object from Masayaki
Suzuki at (I89) and Guy Wells and Daniel Bamberger at (Z80).  The
latter posted an image and some info at

https://twitter.com/NBObservatories/status/1286470009947131904

    The object has H=27,  roughly what you'd expect for the booster,
but I'm not entirely that it is.  I'm labelling it as TianweA
for the moment (MPC frowns on eight-character designations).

    Cut-and-paste this message,  or at least the astrometry shown
below,  into

https://www.projectpluto.com/fo.htm

    and you can get custom ephemerides for TianweA good to about an
arcminute.  (We also have some astrometry from ATLAS -- they caught
the object early on and put it on NEOCP -- but it confuses Find_Orb
and we really aren't supposed to distribute it anyway... fortunately,
we don't absolutely need it in this case.)

    You'll see at the above Twitter post that NBO also spotted a
second object,  fainter by about three arcminutes,  about 3.6'
west and 3.6' north.  They got one position,  so this is awaiting
confirmation;  it might just be an artifact.

    I also have a report of yet _another_ object,  roughly as
bright as TianweA,  but about 22' west and 25' to the south.  Not
enough astrometry for a reliable orbit,  but I think if you look
at that offset from TianweA,  it should be easy to find.

    Seems there's been some tracking of the signal from the
spacecraft :

https://twitter.com/uhf_satcom
https://twitter.com/df2mz

    which suggests to me that we'll be able to figure out which
is the spacecraft and which is the booster,  and possibly add
some of their data to the mix.

-- Bill

COD I89
CON M. Suzuki, 9-12-17 Kouei-nishi-machi, Kitami-shi, Hokkaido 090-0058, Japan
CON  [mtnsuzuki at nifty.com]
COM Tianwen-1 booster
OBS M. Suzuki
MEA M. Suzuki
TEL 0.15-m f/7.3 refractor + CCD
ACK I89 ART SAT Tianwen-1 booster 2020-07-24 11:39:00 Suzuki
AC2 mtnsuzuki at nifty.com
NET Gaia DR2
COM =      TianweA
Tianwen-1     C2020 07 24.09738 00 46 31.26 +14 59 59.3          15.7 G      I89
Tianwen-1     C2020 07 24.10042 00 46 29.86 +15 00 30.6          15.9 G      I89
Tianwen-1     C2020 07 24.10354 00 46 28.40 +15 01 02.1          15.7 G      I89
Tianwen-1     C2020 07 24.10762 00 46 26.39 +15 01 42.7          15.9 G      I89
----- end -----


COM =      TianweA
# version=2017
# observatory
! mpcCode Z80
! name Northolt Branch Observatory
# submitter
! name D. Bamberger
# observers
! name G. Wells
# measurers
! name D. Bamberger
# telescope
! design Ritchey-Chretien
! aperture 0.25
! fRatio 8.0
! detector CCD
# software
! astrometry Astrometrica 4.12.0.448
! photometry Astrometrica 4.12.0.448
permID |provID     |trkSub  |artSat      |mode|stn |obsTime                |ra         |dec        |rmsRA|rmsDec|astCat  |mag  |rmsMag|band|photCat |photAp|logSNR|seeing|exp |rmsFit|nStars|notes|remarks
        |           |  Probe2|            | CCD|Z80 |2020-07-23T23:42:43.0Z | 11.46081  |+14.40392  |0.23 |0.21  |   Gaia2|15.5 |0.06  |   G|   Gaia2| 7.9  |1.59  |3.9   | 100|0.17  |    74|K    |
        |           |  Probe2|            | CCD|Z80 |2020-07-23T23:44:23.0Z | 11.46280  |+14.40863  |0.25 |0.23  |   Gaia2|15.5 |0.06  |   G|   Gaia2| 7.9  |1.46  |4.0   | 100|0.19  |    76|K    |
        |           |  Probe2|            | CCD|Z80 |2020-07-23T23:46:03.1Z | 11.46494  |+14.41339  |0.23 |0.24  |   Gaia2|15.6 |0.07  |   G|   Gaia2| 7.9  |1.46  |4.0   | 100|0.18  |    81|K    |