USA 116 search elset

From: Björn Gimle (bg_26934@glocalnet.net)
Date: Thu Mar 02 2006 - 05:12:40 EST

  • Next message: Peter Wakelin: "SATOBS 2006 March 01-02"

    I have failed a number of times to find USA 116 over periods up to
    -5/+10 minutes from the last known amateur elset:
    
    05249.USA 116
    1 23728U 95066A   05249.06868391 0.00001700  00000-0  86728-4 0    05
    2 23728  97.8648  18.4474 0285000  66.4251 293.5748 14.87800711    08
    
    On March 01 2006 it could be about:
    06060.USA 116 search
    1 23728U 95066A   06060.00000000  .00001340  00000-0  68362-4 0    11
    2 23728  97.8648 193.2006 0283660 207.3796 265.9304 14.88274589 26166
    
    In this 176 day interval the AOP decreased from  66.4251 to about 207
    by about 3.36 deg/day, ie it passed 0 twice and 180 once.
    Near these times (perigee at equator) drag usually increases.
    
    So I interpolated the MeanMotion from my available elsets at the
    times AOP had these values, and computed the average drag factor
    ndot2 from these over the years when eccentricity is about .030.
    I also computed ndot2 for USA 161 for the same dates - not the
    same AOP. So these average values should reflect the atmospheric
    conditions over the intervals, but could deviate in size.
    (Using consecutive elsets instead gives extremely irregular
    results for these relatively low-drag satellites)
    
    In fact the values do show the expected strong correlation, and
    I arrived at ndot2=.00001340 for this period, and Vec2TLE.exe
    gave me the search elset above.
    
    Unfortunately I have not had the weather to test this elset,
    and forecasts for the next five days do not look better.
    
    -- Björn Gimle                                        --
    -- COSPAR 5919, MALMA,    59.2615 N, 18.6206 E, 33 m  --
    -- COSPAR 5918, HAMMARBY, 59.2985 N, 18.1045 E, 44 m  --
    -- COSPAR 5920, FRUVIK,   59.3260 N, 18.4820 E, 11 m  --
    
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