[neo_followup] Improved 1964-054A = OGO-1 data, ephems

[Bill Gray]

    Just got my first post-perigee data.  The object was a few
arcminutes off prediction (8' north, 6' east),  corresponding
to an AMR of 0.046.  So modify my earlier message : if you
turn on SRP and constrain A=0.046,  you'll nail the object
within an arcsecond or two.  More later...

-- Bill

On 8/27/20 11:30 AM, Bill Gray wrote:
> Hello all,
> 
>     I found quite a bit of additional data for this object in
> my inbox this morning (thank you!).  At present,  I've got
> 46 observations from the current orbit :
> 
> https://www.projectpluto.com/temp/ogo1.txt
> 
>     A correction to my previous e-mail : you can just download
> the above file and feed it into Find_Orb,  either "current"
> Windows or Linux,  or on-line,  or the old Windows GUI version,
> and compute ephemerides for your location that should be good
> to within a few arcminutes.  That's about the level of effect
> I expect the upcoming perigee (occurring as I write) to have.
> 
>     You can still turn on solar radiation pressure (by hitting
> the '*' key) and constrain the area/mass ratio to be A=0.03,
> and get suitably adjusted results.  But unless you have a
> small field of view,  the non-SRP version should at least let
> you find the object.
> 
>     The good news is that,  if the nominal AMR makes a five
> arcminute difference (300") and the object is measured to an
> arcsecond,  it means the effects of atmospheric drag during
> that pass will be measured to about one part in 300.  Which
> is pretty good.  And we'll probably get enough data to
> _really_ nail down the re-entry time and location.
> (Currently looks to be at about 21:00 UTC on the 29th over
> French Polynesia,  but a little more or less drag could
> make that prediction look stupid.)
> 
>     This may be a useful exercise to prepare for something
> like the 1972 fireball that zipped through the atmosphere,
> lost lots of speed,  and probably was left in Earth orbit
> and crashed at the next perigee.
> 
> -- Bill