Re: NROL-101 manoeuvre imaged from Joshua Tree?

From: Bob Christy via Seesat-l <>
Date: Sun, 15 Nov 2020 13:52:53 +0000
It isn't inconsistent with HEO but it would imply injection into HEO transfer orbit at ~01:30 UTC near southern apex of rev 2 rather than the expected rev 0.

I've based this on the assumption that the photographer's "6:30ish" means ~02:30 UTC.

Bob Christy

> On 15 Nov 2020, at 09:31, C. Bassa via Seesat-l <> wrote:
> ´╗┐Hi all,
> The image and video that Marco and Scott discovered provide some
> interesting clues to the NROL-101 orbit. If we assume this is the fuel
> dump of the Centaur upper stage, I think they seem to rule out the
> Molniya hypothesis, as both images suggest the fuel dump was visible
> around 02:30UTC, about 4 hours after launch.
> For a Molniya orbit, the burn from the parking orbit to Molniya would
> occur around 23:36UTC, and on geostationary transfer missions, S/C sep
> is usually about 30 minutes after launch, with the Centaur CCAM
> (collision and contamination avoidance maneuver) shortly afterwards
> (within an hour?). For the Molniya orbit elements that Ted estimated,
> the payload and Centaur would be nearing apogee at 02:30UTC.
> My guess would be that the NROL-101 payload went to a MEO orbit, where
> the Centaur performed a burn from the parking orbit to a transfer
> orbit, as well as a circularization burn at the first apogee. The fuel
> dump then occurred after circularization. This hypothesis would be
> strengthened by the fact that the Centaur did not have a deorbit area
> and has been catalogued by CSpOC. Jonathan McDowell kindly recorded
> that at 01:49UTC (launch +3h17m), ULA called mission success.
> It may be possible to determine the altitude of the MEO orbit from the
> motion of the fuel dump cloud and the timing of mission success. I
> will try to investigate.
> Regards,
>     Cees
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