n.falla@btopenworld.com Apr 9, 2009
--- In find_orb@yahoogroups.com, Bill J Gray <pluto@...> wrote:
>
> 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
>