Observation arc 2004 Apr 20.37 - 25.16 UTC: 03790B 0.0 0.0 0.0 3.5 v 1 90019U 03790B 04116.14322083 .00309584 00000-0 82077-3 0 02 2 90019 27.3315 115.7933 1350398 267.8748 76.7032 13.12355347 01 WRMS residuals = 0.015 deg I find that for this object, SGP4 does not cope well with arcs greater than about 5 days. It will fit some observations over a longer arc, but not all. Those that appear as outliers tend to be clumped together, e.g. all observations made on given pass. Could this have something to do with SGP4's dropping of the higher order terms in its propagation of semi-major axis for orbits of perigee height below 220 km? 03790B's is near 200 km. The much-observed Cosmos 398 had a similar perigee height: 1 04966U 71016A 93179.05712837 .00094832 28748-4 25353-3 0 2883 2 04966 51.4678 200.3108 1351875 95.1545 280.4588 13.12549157724973 It will be interesting to see whether or not SGP4 copes any better with this orbit. If not, then I will want to compare against orbits of perigee greater than 220 km. Ted Molczan ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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