NROL-71 is scheduled for launch from VAFB aboard a Delta IV-Heavy on 2019 Jan 19 at 19:05 UTC. Justin Ray will live-blog the launch for ULA: https://www.ulalaunch.com/missions/delta-iv-nrol-71 Stephen Clark will live-blog the launch for Spaceflight Now: https://spaceflightnow.com/2018/12/07/delta-382-mission-status-center/ I believe that the payload is the first Block 5 KH-11. My payload speculation post is here: http://satobs.org/seesat/Dec-2018/0058.html 1. Planar window The launch times published to-date reveal that the window is planar, i.e. targeting a specific plane or range of planes: 2018 Dec 08 04:19 UTC 2018 Dec 09 04:06 2018 Dec 19 01:57 2018 Dec 20 01:44 2018 Dec 21 01:31 2019 Jan 19 19:05 I am not aware of an existing satellite in orbit with which the payload could form a constellation or rendezvous, so I am puzzled by the existence of a planar window. Over 43 days, the window moved 554 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 The rate of precession is a function of inclination, mean motion and eccentricity, so this is a strong clue to the planned final orbit of the satellite. 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. The rate of precession is much more sensitive to inclination than to mean motion and eccentricity; therefore, even a small uncertainty in inclination results in a large uncertainty in mean motion. Below are the mean motion and eccentricity that yield -2.27 deg/d RAAN precession, that bracket the range of inclination: Inc n0 e0 Per Apo 73.5 15.5095 0.02246 259 564 74.0 15.7143 0.01386 259 446 74.5 15.9268 0.00498 259 325 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. The initial orbit could be a little lower or higher than tabulated above. The last two KH-11s made small apogee boosts a few days after launch. 2. Visibility windows Based on limited checks, it appears that about 5 days after launch, morning visibility will open for far northern observers, and evening visibility will open for mid-southern latitude observers. Prospective observers should check for local visibility. 3. Search elements The search elements are based on launch on 2019 Jan 19 at 19:05 UTC. I intend to issue revisions in the event of material new information or launch delays. There are pairs of TLEs for inclination 74.5 deg, 74 deg, and 73.5 deg. In each pair, one TLE has argument of perigee that yields apogee passes near mid-latitudes; the other has argument of perigee that yields perigee passes. This is intended to help bracket the minimum and maximum predicted elevation above the horizon. Each TLE is labelled to indicate whether it yields apogee or perigee passes at mid-northern latitudes. Southern hemisphere observers can use the same TLEs by swapping the apogee and perigee labels. The RAAN of each TLE could be off by at least 1 deg. Along-track prediction time uncertainty is at least a couple of minutes. apogee 259 X 325 km 1 71907U 19019.79965274 .00000000 00000-0 00000-0 0 06 2 71907 74.5000 116.0887 0049782 323.0000 181.3000 15.92677149 05 perigee 259 X 325 km 1 71908U 19019.79965273 .00000000 00000-0 00000-0 0 06 2 71908 74.5000 116.1137 0049782 110.0000 33.8000 15.92677149 00 apogee 259 X 446 km 1 71909U 19019.79965272 .00000000 00000-0 00000-0 0 06 2 71909 74.0000 116.8587 0138590 305.0000 199.5000 15.71434437 02 perigee 259 X 446 km 1 71910U 19019.79965271 .00000000 00000-0 00000-0 0 07 2 71910 74.0000 116.8937 0138590 115.0000 28.2000 15.71434437 00 apogee 259 X 564 km 1 71911U 19019.79965270 .00000000 00000-0 00000-0 0 07 2 71911 73.5000 117.6587 0224609 305.0000 199.6000 15.50949585 08 perigee 259 X 564 km 1 71912U 19019.79965269 .00000000 00000-0 00000-0 0 06 2 71912 73.5000 117.6787 0224609 125.0000 18.0000 15.50949585 05 This launch has already presented a huge surprise in the orbital inclination; there could well be more. Happy hunting! Ted Molczan _______________________________________________ Seesat-l mailing list http://mailman.satobs.org/mailman/listinfo/seesat-lReceived on Tue Jan 15 2019 - 13:29:40 UTC
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