NROL-35 is scheduled for launch on 2014 Dec 13 at 03:13 UTC, from Vandenberg AFB, aboard an Atlas V-541. http://spaceflightnow.com/2014/12/10/nrol35-mission-status-center/ The payload probably is the next HEO SIGINT, hosting SBIRS-HEO 3. NROL-42, expected to launch in a couple of years from VAFB on the same model of rocket, appears to be the same type of mission. The last launch in the series was NROL-28 in March 2008, from VAFB on an Atlas V-411. Its payload is known as USA 200 (08010A / 32706). The Atlas V-541 has roughly 40 percent greater performance than the Atlas V-411, which suggests that NROL-35 will carry a significantly heavier payload. Some of the extra performance will be used to de-orbit the Centaur stage on its first revolution, to impact in the Indian Ocean south of Australia. Assuming launch at the above time, and a mission identical to NROL-28, these would be the approximate initial orbits of payload and Centaur: Payload 1117 X 37562 km 1 72001U 14347.15821761 .00000000 00000-0 00000-0 0 03 2 72001 63.5608 209.8666 7085471 271.7444 359.8457 2.10489866 03 Centaur CCAM 1087 X 37455 km 1 73001U 14347.17905093 .00000000 00000-0 00000-0 0 07 2 73001 64.6290 210.5838 7089441 271.7256 15.5928 2.11333612 02 The payload's elements are derived from one of the TLEs we produced from optical tracking of NROL-28, about a week after launch, prior to its first manoeuvre: 1 32706U 08010A 08081.53973202 .00000000 00000-0 00000-0 0 08 2 32706 63.5657 40.6363 7087561 271.7437 15.6600 2.10485232 04 No two missions of this type are likely to have identical initial elements, and given the use of a much different launch vehicle, the actual elements of NROL-35 almost certainly will differ somewhat. The Centaur 73001 TLE derives from backward propagation of recent elements of 08010B / 32707. It reflects the typical CCAM (Collision and Contamination Avoidance Maneuver). Since NROL-35's Centaur is to be de-orbited, its final elements will be different. If the de-orbit manoeuvre occurs at the epoch of the 73001 TLE, then the various constraints could be satisfied by changing the eccentricity, argument of perigee, mean anomaly, and mean motion as follows: Centaur de-orbit -173 X 33549 km 1 73002U 14347.17905094 .00000000 00000-0 00000-0 0 09 2 73002 64.6290 210.5838 7310000 258.7256 18.7000 2.47800000 01 This orbit would impact in the NOTAM zone about 23 min. into the impact window. Delta-V would be about 650 m/s, which does not seem outrageous. Delaying the burn nearly an hour to exactly T+02:00 h, and following the same procedure yields this result: Centaur de-orbit -274 X 33588 km 1 73003U 14347.21736112 .00000000 00000-0 00000-0 0 08 2 73003 64.6290 210.5787 7350000 263.6000 51.7500 2.48300000 09 This orbit would also impact in the NOTAM zone about 23 min. into the impact window, but delta-V would be reduced to about 270 m/s. The above estimates seem reasonable, but NRO launches have the potential for surprise, especially when there is a change of rocket and/or payload. If you have other ideas about the initial orbits and/or payload, please post your analysis. Ted Molczan _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-lReceived on Thu Dec 11 2014 - 19:41:28 UTC
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