NROL-101 search elements

From: Ted Molczan via Seesat-l <seesat-l_at_satobs.org>
Date: Tue, 10 Nov 2020 08:22:01 -0500
ULA is now targeting the launch of NROL-101 for 2020 Nov 12 at 22:18 UTC, from Cape Canaveral, pending range approval.
The launch vehicle is Atlas V-531 with a medium length fairing.

https://spaceflightnow.com/2020/11/02/atlas-5-nrol-101-av-090-mission-status-center/

The NOTAMs reveal that the target orbit is high inclination. I estimate at least a 57 degree parking orbit, perhaps a
few degrees higher.
 
The launch time has regressed 4.44 min/d on average since Nov 3, which is consistent with a planar launch window of a
Molniya orbit.

I speculate that the payload is a 4th generation SDS relay satellite, as discussed in an earlier message:

http://satobs.org/seesat/Nov-2020/0021.html

Marco Langbroek's pre-flight estimated elements are available here:

http://launchtower.langbroek.org/

Here are mine, based on the above launch time:

Parking                                                  209 X 262 km
1 78301U 78301A   20317.97747685  .00000000  00000-0  00000-0 0    07
2 78301  60.0091 294.6717 0040000 106.8858 180.0000 16.14000000    04
MECO2                                                  258 X 16775 km
1 78302U 78302A   20317.97747685  .00010087  00000-0  10000-2 0    08
2 78302  60.0097 294.6725 5544404 286.8848   0.0033  4.77567019    01
Parking                                                  191 X 795 km
1 78303U 78303A   20317.97511574  .00000000  00000-0  00000-0 0    07
2 78303  62.5000 295.7933 0439500  90.0105 180.0266 15.23880000    00
MECO2                                                  727 X 38378 km
1 78304U 78304A   20317.97511574  .00000000  00000-0  00000-0 0    09
2 78304  62.5000 295.7933 7260000 266.0000   0.5000  2.07900000    07

The epoch of these TLEs is close to the time of MECO2.

TLEs 78301 and 78302 are based on the orbits we determined from our optical and radio tracking of the SDS 3-4 launch in
December 2007. The launch vehicle was Atlas V-401.

TLEs 78303 and 78304 are based on the orbits I estimated for SDS 2-5, launched in January 1998 on an Atlas 2A rocket. It
is the only Molniya SDS launched from Cape Canaveral, that the upper stage inserted into nearly its final 2.006 rev/d
orbit. The LEO parking orbit is derived from the partial elements reported to the U.N. The MECO2 orbit is estimated from
the known elements of the Centaur, after numerical propagation to the day of launch.

Happy hunting!

Ted Molczan


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Received on Tue Nov 10 2020 - 07:23:07 UTC

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