NROL-71 is scheduled for launch from VAFB aboard a Delta IV-Heavy on 2018 Dec 19 at 01:57 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 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 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. The orbit will be visible in the northern and southern hemisphere, as discussed in the following section. Based on limited checks, it appears that northern hemisphere observers may initially have morning and evening visibility, and that southern hemisphere observers will have only evening visibility. Prospective observers should check for visibility from their location. 2. Search elements The search elements are based on launch on 2018 Dec 19 at 01:57 UTC. I intend to issue revisions in the event of material new information or launch delays. Pairs of TLEs have been produced, 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. 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. The TLEs have been organized and labelled for northern hemisphere observers, but southern hemisphere observers can use them by swapping evening and morning and apogee and perigee, as discussed in the following sections. 2.1 Morning passes in N. hemisphere This section contains TLEs for morning passes in the northern hemisphere. Each TLE is labelled to indicate whether it yields apogee or perigee passes at mid-northern latitudes. The same TLEs can be used by southern hemisphere observers, but for evening passes. Also, the apogee and perigee labels must be swapped. For example, the 71901 TLE yields northern hemisphere morning passes near apogee, and southern hemisphere evening passes near perigee. apogee 259 X 325 km 1 71901U 18353.08576391 .00000000 00000-0 00000-0 0 00 2 71901 74.5000 187.8700 0049782 235.0000 269.5000 15.92677149 00 perigee 259 X 325 km 1 71902U 18353.08576390 .00000000 00000-0 00000-0 0 00 2 71902 74.5000 187.8550 0049782 55.0000 88.6000 15.92677149 04 apogee 259 X 446 km 1 71903U 18353.08576389 .00000000 00000-0 00000-0 0 09 2 71903 74.0000 188.6400 0138590 235.0000 270.5000 15.71434437 09 perigee 259 X 446 km 1 71904U 18353.08576388 .00000000 00000-0 00000-0 0 09 2 71904 74.0000 188.6350 0138590 55.0000 87.3000 15.71434437 08 apogee 259 X 564 km 1 71905U 18353.08576387 .00000000 00000-0 00000-0 0 09 2 71905 73.5000 189.4000 0224609 235.0000 271.5000 15.50949585 00 perigee 259 X 564 km 1 71906U 18353.08576386 .00000000 00000-0 00000-0 0 09 2 71906 73.5000 189.4300 0224609 55.0000 86.0000 15.50949585 03 2.2 Evening passes in N. hemisphere This section contains TLEs for evening passes in the northern hemisphere. Each TLE is labelled to indicate whether it yields apogee or perigee passes at mid-northern latitudes. These elements differ from their counterparts in the previous section, mainly in argument of perigee. A different leg of the orbit will be visible, which requires different values of argument of perigee to yield passes near perigee and apogee. The same TLEs can be used by southern hemisphere observers, but for morning passes. Also, the apogee and perigee labels must be swapped. For example, the 71907 TLE yields northern hemisphere evening passes near apogee, and southern hemisphere morning passes near perigee. apogee 259 X 325 km 1 71907U 18353.08576385 .00000000 00000-0 00000-0 0 09 2 71907 74.5000 187.8300 0049782 323.0000 181.3000 15.92677149 01 perigee 259 X 325 km 1 71908U 18353.08576384 .00000000 00000-0 00000-0 0 09 2 71908 74.5000 187.8550 0049782 110.0000 33.8000 15.92677149 04 apogee 259 X 446 km 1 71909U 18353.08576383 .00000000 00000-0 00000-0 0 09 2 71909 74.0000 188.6000 0138590 305.0000 199.5000 15.71434437 09 perigee 259 X 446 km 1 71910U 18353.08576382 .00000000 00000-0 00000-0 0 00 2 71910 74.0000 188.6350 0138590 115.0000 28.2000 15.71434437 06 apogee 259 X 564 km 1 71911U 18353.08576381 .00000000 00000-0 00000-0 0 00 2 71911 73.5000 189.4000 0224609 305.0000 199.6000 15.50949585 05 perigee 259 X 564 km 1 71912U 18353.08576380 .00000000 00000-0 00000-0 0 00 2 71912 73.5000 189.4200 0224609 125.0000 18.0000 15.50949585 02 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 Sun Dec 16 2018 - 12:44:00 UTC
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