>OPERATIONAL EXPERIENCE OF THE USE OF A GENERIC PRODUCT FOR COLLISION RISK >ASSESSMENT ON GEOSTATIONARY ORBIT http://www.issfd.dlr.de/papers/P1080.pdf >when five close approaches to GOES-7 were detected in a period of 3 days 1 17561U 87022A 04050.46768113 .00000058 00000-0 10000-3 0 3186 2 17561 8.3108 53.3103 0001830 57.4809 31.4127 1.00288558 45411 The above elset is consistent with the previous elsets. 1 17561U 87022A 04061.98466440 .00000078 00000-0 00000+0 0 3304 2 17561 8.3140 53.2970 0000200 292.7340 354.9150 1.00248806 45525 This one is not. 1 17561U 87022A 04078.59653115 .00000062 00000-0 00000+0 0 3512 2 17561 8.3613 53.1063 0001725 52.8809 111.0617 1.00288986 45691 This one is consistent. The authors admit that such cases are "rare". "An upgrade is being studied to perform historical analysis of the TLE data and, in this way, detect the potential strange events by inspection of the TLE file used, warning the user of such potential problems." Reference 9: Discussion of SDP4 problems by Rob Matson on SeeSat in March, 1997. ----------- For GOES 7, there is a "discontinuity" between these two elsets: 1 17561U 87022A 04145.37495207 .00000126 00000-0 00000+0 0 4230 2 17561 8.4814 52.6007 0006038 103.2954 57.6503 1.00323582 46367 1 17561U 87022A 04160.00000000 +.00000046 +00000-0 +00000-0 0 04412 2 17561 008.5213 052.4427 0003740 037.8302 348.7438 01.00276230046516 There is then one inconsistent elset: 1 17561U 87022A 04177.78841676 .00000076 00000-0 00000+0 0 4600 2 17561 8.5614 52.3749 0002910 44.8066 286.1292 1.00230307 46686 Subsequent elsets are consistent: 1 17561U 87022A 04196.00000000 .00000086 00000-0 00000+0 0 4807 2 17561 8.6029 52.3013 0003140 55.3166 12.1764 1.00289224 46879 There is a similar "jump" in early 2003: 1 17561U 87022A 03013.52827387 .00000116 00000-0 10000-3 0 8102 2 17561 7.5470 55.7264 0004064 288.6625 149.4031 1.00317770 41389 1 17561U 87022A 03039.31434324 .00000057 00000-0 10000-3 0 8443 2 17561 7.5828 55.6050 0005340 259.6270 117.9254 1.00250703 41648 So it appears that GOES 7 is still being controlled in longitude (over a very large range of longitudes). Mike McCants ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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