USA 129's (96072A / 24680) mean motion is now high enough to require a major re-boost. Moreover, its argument of perigee is nearing the equator, as has been the case of many past such manoeuvres. The first re-boost opportunity will occur within a day or two of 2001 May 08 UTC, when USA 129's perigee will cross the equator. If that opportunity passes without a manoeuvre, then the next opportunity occurs about 10 days later, when sister KeyHole USA 116's (95066A / 23728) argument of perigee crosses the equator. One of the advantages of making manoeuvres with perigee near the equator, is the ability to efficiently change several of the orbital elements using a single impulse, including the inclination. The KeyHoles' sun-synchronous orbits are perturbed by the sun's gravity, resulting in oscillation of the inclination. I note that 96072A's inclination has decreased from in excess of 97.95 deg in 1998, to about 97.82 deg, which is about the lowest observed value, suggesting that it is due to be adjusted upward. I also note that in the spring of 1998, 96072A's inclination had declined to about 97.82 deg, just before its major re-boost manoeuvre, after which it was found to have increased to more than 97.95 deg. I have appended several pre and post-manoeuvre elsets that document this change. The first two post-manoeuvre elsets did not reflect the change in inclination, but I suspect that was due to the inclination having been held constant by the analyst(s), pending receipt of a sufficient number of post-manoeuvre observations to confidently re-compute all of the elements. Using 1998 as my precedent, I suspect that 96072A's operators will take advantage of its perigee crossing of 2001 May 08, to increase its inclination to exceed 97.9 deg, as well as re-boost its apogee, within a day or two of that date. Whatever the date of the major re-boost, both KeyHoles can be expected to manoeuvre on that same date. Ted Molczan 96072A's pre and post-maneouvre elements - Spring 1998 1 24680U 96072A 98107.88796393 .00024000 00000-0 23788-3 0 02 2 24680 97.8370 168.6228 0507000 33.0792 326.9207 14.82889041 09 1 24680U 96072A 98107.95605925 .00027220 00000-0 24872-3 0 57 2 24680 97.8216 168.6511 0513577 33.0321 330.1891 14.82899771 4165 1 24680U 96072A 98108.90064327 .00027449 00000-0 27485-3 0 10 2 24680 97.8178 169.5787 0505804 29.3849 333.4817 14.82951788 15 1 24680U 96072A 98108.90064540 .00024829 00000-0 26098-3 0 04 2 24680 97.8321 169.6079 0501810 30.9717 332.0397 14.82942565 05 1 24680U 96072A 98110.85679330 .00027000 00000-0 26831-3 0 09 2 24680 97.8370 171.5481 0506000 23.3416 336.6582 14.83057259 00 1 24680U 96072A 98117.87270499 .00027700 00000-0 27252-3 0 06 2 24680 97.8280 178.4465 0505000 0.3193 359.6806 14.83450297 07 last pre-manoeuvre elset 1 24680U 96072A 98125.86915017 .00027700 00000-0 26006-3 0 02 2 24680 97.8280 186.1920 0550004 334.4276 25.5723 14.74583910 02 1st post-manoeuvre elset 1 24680U 96072A 98129.86815410 .00027700 00000-0 23394-3 0 09 2 24680 97.8280 190.0900 0550004 321.4345 38.5654 14.76385319 09 1 24680U 96072A 98131.15591023 .00018000 00000-0 12437-3 0 04 2 24680 97.9780 191.6605 0565004 317.2494 42.7504 14.76388113 04 1 24680U 96072A 98137.86506743 .00017500 00000-0 11591-3 0 07 2 24680 97.9630 198.2953 0567004 295.7211 64.2787 14.76615585 04 1 24680U 96072A 98140.10125422 .00014000 00000-0 10755-3 0 02 2 24680 97.9590 200.5198 0556004 289.6731 70.3267 14.76648161 01 ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www2.satellite.eu.org/seesat/seesatindex.html
This archive was generated by hypermail 2b29 : Fri May 04 2001 - 10:27:17 PDT