NROL-42 pre-launch elements

From: Ted Molczan via Seesat-l <seesat-l_at_satobs.org>
Date: Tue, 19 Sep 2017 17:24:19 -0400
NROL-42 is scheduled for launch on 2017 Sep 22 at 05:38 UTC, from Vandenberg
AFB, aboard an Atlas V-541.

Live coverage of the launch will be available here:

https://spaceflightnow.com/2017/09/19/av072_journal/

The payload probably is the next HEO SIGINT, hosting SBIRS-HEO 4.

Assuming a planar launch window, in the event of a launch delay, the time of
launch will move earlier by 4 to 5 min. per day.

The last launch in the series was NROL-35 in December 2014, from VAFB on an
Atlas V-541. Its payload is known as USA 259 (14081A/ 40344).

NROL-42's NOTAM co-ordinates are very close to those of NROL-35, which
suggests that it will follow a similar trajectory.

Assuming launch at the above time, and a trajectory identical to that of
NROL-35, these would be the approximate initial orbits of payload and
Centaur:

Payload                                               2101 X 37748 km
1 76800U 76800A   17265.30902778  .00000000  00000-0  00000-0 0    02
2 76800  62.8507 166.9998 6776181 266.7216  35.2910  2.03510114    02

Apex of Centaur plume                                 2101 X 37748 km
1 76801U 76801A   17265.30956019  .00000000  00000-0  00000-0 0    01
2 76801  62.8507 166.8101 6776198 267.5176  35.0425  2.03510083    04

Centaur de-orbit                                      -140 X 33613 km
1 76802U 76802A   17265.30956020  .00000000  00000-0  00000-0 0    05
2 76802  63.9343 167.4723 7301375 253.5845  40.8155  2.47023627    07

The payload's elements (76800) are based on the TLE I derived from early obs
of NROL-35 by Peter Wakelin and Scott Tilley:

http://www.satobs.org/seesat/Dec-2014/0096.html

The Centaur's elements (76801 and 76802) are based on the TLEs that Cees
Bassa derived from observations of the NROL-35 fuel dump by William Stewart:

http://www.satobs.org/seesat/Dec-2014/0230.html

The epoch of the Centaur TLEs corresponds to the approximate time of the
fuel dump: about 07:25 UTC (MET 01h43m).

I have not attempted to adjust 76802 to exactly match the NOTAM de-orbit
zone.

Ted Molczan


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Received on Tue Sep 19 2017 - 16:25:05 UTC

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