RE: BY C 041214

From: Ted Molczan via Seesat-l <seesat-l_at_satobs.org>
Date: Sun, 13 Apr 2014 03:23:14 -0400
Brad Young wrote:

> If I get time, I'll double check star field of last point for OFEQ 10 Ted had to kick.
> It would really help if all UNIDs would pass between bright, well known pairs and
> asterisms in future. At least the fast retrograde motion made it obvious.

Using the estimated TLE I posted Saturday, I found an asterism similar to the one that you reduced to obtain your third
point, but about 10 s further along-track. I am not certain of the geometry you used in your reduction, but it appears
to have been an appulse; applying approximately the same position angle and angular miss-distance to what I believe was
most likely the correct star, yields the third position below:

39650 14 019A   8336 F 20140412021354430 17 25 1334793+551697 48 S
39650 14 019A   8336 F 20140412021402340 17 25 1307069+620478 18 S
39650 14 019A   8336 G 20140412021441860 17 25 0619031+725444 48 S

I weighted point #1 at 50 percent because the time seemed off by one second or so. Allowing all but eccentricity,
argument of perigee and rate of decay to vary yields:

Ofeq 10                                                  383 X 620 km
1 39650U 14019A   14102.09307870  .00000000  00000-0  00000-0 0    03
2 39650 140.9339 218.7020 0172000  64.0412  16.4919 15.22366469    05
Arc 20140412.09-0412.09 WRMS resid 0.377 totl 0.053 xtrk

This should be accurate to within about 1 minute of time per 24 h from epoch.

You did well to spot it, especially given the inaccuracy of the TLE you relied on, which was based on the wrong time of
launch, and was obsoleted by the apparent subsequent manoeuvre to raise the perigee.

Ted Molczan


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Received on Sun Apr 13 2014 - 02:24:04 UTC

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