NROL-42 estimated elements

From: Ted Molczan via Seesat-l <seesat-l_at_satobs.org>
Date: Sun, 24 Sep 2017 01:52:54 -0400
NROL-42 was launched on 2017 Sep 24 at 05:49:47 UTC, from Vandenberg AFB,
aboard an Atlas V-541.

The ascent is in progress as I write. Live coverage of the launch is
available here:

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

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

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 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   17267.31721066  .00000000  00000-0  00000-0 0    04
2 76800  62.8507 171.9250 6776181 266.7216  35.2910  2.03510114    09

Apex of Centaur plume                                 2101 X 37748 km
1 76801U 76801A   17267.31774307  .00000000  00000-0  00000-0 0    02
2 76801  62.8507 171.7353 6776198 267.5176  35.0425  2.03510083    08

Centaur de-orbit                                      -140 X 33613 km
1 76802U 76802A   17267.31774308  .00000000  00000-0  00000-0 0    05
2 76802  63.9343 172.3975 7301375 253.5845  40.8155  2.47023627    01

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 07:37 UTC (MET 01h43m).

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

Ted Molczan


_______________________________________________
Seesat-l mailing list
http://mailman.satobs.org/mailman/listinfo/seesat-l
Received on Sun Sep 24 2017 - 00:53:51 UTC

This archive was generated by hypermail 2.3.0 : Sun Sep 24 2017 - 05:53:52 UTC