It is possible that Iridium plc has made the first tentative move in its plan to de-orbit its Iridium satellites. Iridium 9 (#24828 = 97- 30 C) was, until September 13, in an "operational" near-circular orbit between altitudes of 779 and 776 km, with an orbital period of 100.40 minutes. Orbital element sets issued since then show it some 29 km lower - the latest elset has it in a 750x747 km orbit with a period of 99.79 minutes. The last pre-manoeuvre elset is... Iridium 9 4.0 1.8 0.0 6.0 d 13 779 x 776 km 1 24838U 97030C 00257.91101238 -.00000166 00000-0 -66348-4 0 4242 2 24838 86.3974 27.7289 0001875 80.7395 279.3927 14.34215052169723 ...the next one is... Iridium 9 4.0 1.8 0.0 6.0 d 13 750 x 746 km 1 24838U 97030C 00258.60576252 .00250387 00000-0 71655-1 0 4065 2 24838 86.4479 27.4432 0002500 123.2016 236.9519 14.43260369169828 and the latest elset is... Iridium 9 4.0 1.8 0.0 6.0 d 13 750 x 747 km 1 24838U 97030C 00262.97412783 .00001950 00000-0 57606-3 0 4677 2 24838 86.4572 25.6175 0002779 108.8197 251.3316 14.43074137170456 Small variations in the elsets since September 14 might be caused by further minor manoeuvres, though my suspicion is that they are due to inaccuracies in SpaceCom's determination of the new orbit. While this might be the first indication that the Iridiums are really on the way down, other possibilities, including a satellite malfunction, cannot be ruled out. Alan -- Alan Pickup / COSPAR 2707: 55d53m48.7s N 3d11m51.2s W 156m asl Edinburgh / SatEvo & elsets: http://www.wingar.demon.co.uk/satevo/ Scotland / Decay Watch: http://www.wingar.demon.co.uk/satevo/dkwatch/ ----------------------------------------------------------------- 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
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