Iridium 30 and 31 do indeed have appeared to have exchanged places in the constellation on September 19-22, 2002. Many thanks, Walter, for highlighting this. I had missed this swap entirely, but have now trawled back through saved elsets to work out what happened! Up to and including September 18, 2002, Iridium 30 was followed in the regular pattern by Iridium 31: IRIDIUM 30 1 24949U 97051F 02261.14806094 -.00000231 00000-0 -89653-4 0 8872 2 24949 86.3995 17.9087 0002209 56.9878 303.1529 14.34213466262410 IRIDIUM 31 1 24950U 97051G 02260.87532995 -.00000360 00000-0 -13554-3 0 8889 2 24950 86.3993 18.0069 0002271 58.9272 301.2147 14.34212368262382 IRIDIUM 30 1 24949U 97051F 02261.84574731 -.00000193 +00000-0 -76017-4 0 08944 2 24949 086.3998 017.6177 0002235 060.2566 299.8858 14.34213526262515 IRIDIUM 31 1 24950U 97051G 02261.85209058 -.00000211 +00000-0 -82404-4 0 08986 2 24950 086.3990 017.5985 0002292 063.4936 296.6506 14.34213018262526 A day later, Iridium 30 had been raised and Iridium 31 lowered: IRIDIUM 30 1 24949U 97051F 02262.68297198 .00066488 00000-0 24949-1 0 8880 2 24949 86.4041 17.2727 0002372 77.9375 276.0562 14.31204631262633 IRIDIUM 31 1 24950U 97051G 02262.68931529 .00036298 00000-0 12095-1 0 8891 2 24950 86.4053 17.2485 0002117 83.7475 282.6644 14.37378306262644 IRIDIUM 30 1 24949U 97051F 02264.36216666 -.00003261 00000-0 -12451-2 0 8921 2 24949 86.4020 16.5744 0002307 79.9658 280.1786 14.31170241262874 IRIDIUM 31 1 24950U 97051G 02264.42850689 -.00002106 00000-0 -71311-3 0 8927 2 24950 86.4037 16.5201 0002285 89.2377 270.9082 14.37355916262897 On this basis, Iridium 31 would have overtaken Iridium 30 at around 15:00 on September 20, 2002. Subsequent elsets show Iridium 31 preceding Iridium 30 in the regular pattern: IRIDIUM 30 1 24949U 97051F 02266.59952037 -.00107328 00000-0 -38984-1 0 8935 2 24949 86.4056 15.6428 0002675 71.8218 304.7160 14.34168198263199 IRIDIUM 31 1 24950U 97051G 02266.58661706 -.00070580 00000-0 -25474-1 0 8935 2 24950 86.4059 15.6161 0003051 92.4409 250.2627 14.34220528263209 Over the next few days, minor adjustments appear to have been made to get the satellites into precise new positions. I have no idea at all of the reason for this changeover! One possibilty is that one or other or the satellites had a failed cross-link antenna and was repositioned to match with a corresponding failed cross-link antenna on a satellite in an adjacent orbital plane. But that is pure guesswork! I have incorporated this change into my iridium web page http://www.rod.sladen.org.uk/iridium.htm I have rechecked the whole Iridium constellation formation as of yesterday, and there do not seem to have been any other changes that we have missed! -- Rod Sladen Beeston, Nottinghamshire, UK 52.923N, 1.219W ----------------------------------------------------------------- To unsubscribe from SeeSat-L, send a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@satobs.org List archived at http://www.satobs.org/seesat/seesatindex.html
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