NROL 129 search elements

From: Ted Molczan via Seesat-l <seesat-l_at_satobs.org>
Date: Tue, 28 Jul 2020 13:15:08 -0400
Russell Eberst observed an UNID on 2020 July 26 UTC that "looked like a standard Starlink satellite". Visual magnitude was 5.7.

http://satobs.org/seesat/Jul-2020/0139.html

The observation does not appear to correlate with any objects in orbits that are currently known to us.

I offer the following speculative solution.

Russell's observation was not far from the predicted plane of the NROL 129 launch, which occurred on July 15. I estimated inclination of 50 deg, based on the NOTAMs, and posted search TLEs for 400 km, 500 km and 600 km circular orbits.

The 600 km version was closest to Russell's observation, but too low in declination.

A quasi-54 deg orbit could be forced to fit.

The following search TLE is based on the assumption that the initial trajectory was of 50 deg inclination, but that the fourth stage burned out-of-plane to increase the inclination. I guessed that this occurred 700 s after launch, near 18.5 N, 53 W. Since the burn was not at a node, the RAAN would have shifted a couple of degrees west. The elements were adjusted by trial and error to agree with Russell's observation.

NROL 129 search                                          601 X 603 km
1 79399U 79399A   20197.58171296  .00000000  00000-0  00000-0 0    05
2 79399  53.6300 284.4500 0001000   0.0206 157.0000 14.88740000    03

I consider this a long-shot, but perhaps worth a look to see whether anything is there. Allow for at least several minutes of prediction time uncertainty.

If the object proves to belong to the NROL 129 launch, then it may be the Minotaur 4th stage.

Russell's 310 observations of two Minotaur 4th stages (10048B / 37169 and 10062G / 37228) yield a standard visual magnitude of 6.4 (1000 km, 90 deg phase angle), with co-efficient of phase of 0.837 mag/rad. The prediction interval is +/-1.2 mag, with 95% confidence.

An object with that std mag, in the above orbit, in the circumstances of Russell's observation, would have had predicted mag of 5.7 +/- 1.2. 

Ted Molczan





_______________________________________________
Seesat-l mailing list
http://mailman.satobs.org/mailman/listinfo/seesat-l
Received on Tue Jul 28 2020 - 12:16:20 UTC

This archive was generated by hypermail 2.3.0 : Tue Jul 28 2020 - 17:16:20 UTC