Hi Norman,
"...One tiny point: my display on the impact latitude
lacks a North/South."
Ouch! Thanks for mentioning this. I'll be posting the
fix in a day or two, allowing for any other possible error
reports.
You can get the actual data for 2008 TC3 here:
http://newton.dm.unipi.it/~neodys/mpcobs/2008TC3.rwo
This file is in OrbFit format, but Find_Orb can open
and read it anyway. (This is a useful thing to remember
generally, not just for 2008 TC3. I've made frequent use
of NEODyS and AstDyS for getting astrometric data. I'm
not sure they are really supposed to do this, but I've
often been glad they do.)
Or you can get the original discovery data here:
http://www.cfa.harvard.edu/mpec/K08/K08T50.html
...with follow-up data in a dozen or so subsequent
MPECs (just click on the 'next MPEC' arrow).
My initial determination that 2008 TC3 was a likely
impactor was based on just the (G96) and (854) data from
the above MPEC. At the time, I could only say that it
had about a 90% chance of impacting. With the (D90)
data, things narrowed down quickly to northern Sudan.
And with further data, it was nailed down to within
a kilometer or so.
"...If anybody gets one of these for real, I suggest
that you call it in to MPC ASAP..."
And possibly make a plea for observations on MPML. When I
noticed this was a likely impactor, it had been some time
since the (G96) and (854) observations had been made, and I
was pessimistic about recovery. (Unduly so, as it turned out:
the ephemeris uncertainty when (D90) recovered it was only a
few arcminutes, and never rose above a few arcseconds after
that.) But it would be a shame if another such object was
found and left to languish on NEOCP, with no note made that
very close attention should be paid to it.
Also, such objects might never get noticed. The motion
of 2008 TC3 was not remarkable at discovery. The only reason
I noticed it was that the NEOCP ephemeris showed it moving slowly,
slowly, getting brighter... then suddenly zipping by at
tremendous speed about 17 hours later. So I downloaded the
observations and investigated.
Had impact been, say, 27 hours later, I'd not have noticed
that it was a likely impactor.
-- Bill