03790B elements

From: Ted Molczan (molczan@rogers.com)
Date: Sun Apr 25 2004 - 10:23:20 EDT

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    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
    
    
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