Marco Langbroek wrote: > Hi all, > > New date for the NROL-71 launch: Dec 18th. > > - Marco > > > > > Media Update: ULA Delta IV Heavy NROL-71 Set to Launch > > > > (Vandenberg Air Force Base, Calif., Dec. 13, 2018) – A United Launch Alliance Delta IV > Heavy carrying the NROL-71 mission for the National Reconnaissance Office is set to launch > on Tuesday, Dec. 18. The mission will lift off on a Delta IV Heavy launch vehicle from Space > Launch Complex-6 at Vandenberg Air Force Base in California. The launch time is 5:57 p.m. > PST. This confirms that the launch window is planar, and moves earlier at the approximate rate of 13 min/d. Below are the UTC launch times published to-date: 2018 Dec 08 04:19 2018 Dec 09 04:06 2018 Dec 19 01:57 Over 11 days, the window moved 142 min. earlier, or about 12.9 min/d. The rate of precession of the RAAN is: = 360 * (1.00273790934 - 1440/(1440 - 12.9)) = -2.27 deg/d Analysis of the NOTAM data reveals the target inclination to be about 74 deg. My guess is that the uncertainty is less than 0.5 deg. Below are the mean motion, eccentricity, perigee, and apogee height (km) that yield -2.27 deg/d RAAN precession, over the range of inclination: Inc n0 e0 Per Apo 73.5 15.5023 0.02311 259 573 74.0 15.7070 0.01454 259 455 74.5 15.9196 0.00566 259 335 If the payload is a KH-11, then given the disclosure that the new generation will retain the existing mirror diameter of 2.4 m, its perigee height should be near the existing value of 259 km, which I used to constrain the above estimates. If 74 deg proves correct, then the orbit will have the dimensions of the pre-1985 KH-11, but with an unprecedented inclination. USA 186 (05042A / 28888) has been in the pre-1985 sun-synchronous (96.9 deg) orbit for the past four years, on its extended mission. At the Dec 09 launch attempt, the orbit was just about to precess into northern hemisphere evening visibility. I will produce search TLEs well in advance of the launch. Ted Molczan _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-lReceived on Thu Dec 13 2018 - 17:08:39 UTC
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