NROL-42 is scheduled for launch on 2017 Sep 24 at 05:30 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. The launch window is planar; therefore, 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 17267.30347222 .00000000 00000-0 00000-0 0 01 2 76800 62.8507 166.9656 6776181 266.7216 35.2910 2.03510114 03 Apex of Centaur plume 2101 X 37748 km 1 76801U 76801A 17267.30400463 .00000000 00000-0 00000-0 0 00 2 76801 62.8507 166.7759 6776198 267.5176 35.0425 2.03510083 02 Centaur de-orbit -140 X 33613 km 1 76802U 76802A 17267.30400464 .00000000 00000-0 00000-0 0 03 2 76802 63.9343 167.4381 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 07:17 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-lReceived on Fri Sep 22 2017 - 23:19:31 UTC
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