[Neocp_artsats] WMAP returning to visibility

[Bill Gray]

Hi folks,

    WMAP (Wilkinson Microwave Anisotropy Probe) spent about nine years 
at the Earth-Sun L2 point,  and was routinely spotted by the asteroid 
surveys.  On 2010 Oct 19,  it did a burn to put it into end-of-life 
heliocentric "graveyard" orbit.

    It's about to come back from the graveyard.  It has completed 13.3 
orbits,  and the earth has completed 14.3 orbits,  and we will catch up 
to it and pass it in early April.  It'll pass almost exactly through 
opposition at a hair under ten million kilometers,  and should reach mag 
21 or 22.

    Details are a little fuzzy.  Horizons has ephemerides,  but not for 
dates/times after the final burn.  I've computed two orbits,  one based 
solely on astrometry after that burn (the object was last observed by 
Peter Birtwhistle at (J95) on 2011 Jan 9 and 19),  and another using 
data from both before and after the burn and solving for the time and 
delta-V of that burn :

https://github.com/Bill-Gray/tles/blob/master/wmap.tle#L58
https://github.com/Bill-Gray/tles/blob/master/wmap2.tle#L58

    Both lead to plausible results that differ by about 45' at closest 
approach.  (And in reality,  non-gravs may make it worse that that.)

    Back when it was active,  I was communicating with three people at 
NASA about it,  and got the "final" ephems for it... which I now can't 
find.  I'd really like to compare the official version to what I'm 
getting from the optical.  (Horizons has WMAP ephems,  but not for 
dates/times after the final burn.)

    Back in 2010,  I was told that "WMAP did its last departure maneuver 
on October 19th 2010 from 20:20:00.0 UTCG to 21:24:11.4 UTCG.  The 
maneuver magnitude was about 27.67 m/s".  I'm getting mid-time of the 
burn at 20:53 and a magnitude of 27.67 +/- 0.02 m/s,  which is 
encouragingly good agreement from totally different datasets and 
procedures.  (Well,  I'm reasonably sure the NASA version didn't use any 
optical data.)

    I've sent in an inquiry to the three e-mail addresses I have.  Two 
bounced (not everybody is still at NASA 14.3 years later).  Fingers 
crossed on the third...  it'd be nice to get a recovery on this object.

    Both of my ephems are available at

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

    (look for the "2001-027A = WMAP (soln 1)" and "2001-027A = WMAP 
(soln 2)" check-boxes.)  If the surveys stumble across it,  and it's 
within three degrees of prediction,  it should get identified.

-- Bill