Re: Now where's the champain = I see the unid sat :)

From: C. Bassa (cgbsat@gmail.com)
Date: Sun Jul 14 2013 - 20:23:09 UTC

  • Next message: Derek C Breit: "DCB Obs JUL 14th UT - USA129 - FIA Radar 2 - etc"

    Hi Kevin, Mike, all,
    
    After adapting some of my software I am now able to do brute force
    parameter searches to find the best fitting orbital elements. The software
    creates a grid of mean motion and eccentricity values and for each pair it
    fits the remaining parameters and stores the rms of the fit. If the
    observations cover enough of the orbit there will be a minimum some where
    in the plane spanned by mean motion and eccentricity, which is where the
    elements fit the observations best.
    
    The software was used on Kevin's slow unknowns from April 4 (object 99300),
    July 6 (object 99208) and July 13 (object 99209). For the latter there is a
    clear minimum around a mean motion of 4.1 revs/day and eccentricity near
    0.6. In the case of 99208 the observational arc is short so the minimum is
    very broad, but it shows that for a given pair of mean motion and
    eccentricity the fits give similar values for inclination, argument of
    perigee, RA of ascending node and mean anomaly to the fits to object 99209.
    This confirms that the observations of July 6 and 13 belong to the same
    object.
    
    This is the best fit orbit, which has very small residuals (0.02 deg rms).
    1 99208U 13594A   13190.79412873  .00000000  00000-0  00000-0 0    08
    2 99208  20.1181 285.3465 5983547 150.2423 150.9703  4.12069308    02
    
    This is an approximate search orbit, and with a perigee of 223 km the Bstar
    drag term might be quite large; expect the object to be early or late.
    
    Furthermore, the parameter searches show that the object of April 4 (object
    99300) is not the same; here the best fit parameters suggest a mean motion
    of 2.5 revs/day with an eccentricity near 0.7, combined with very different
    values of the other orbital parameters.
    
    I hope that this analysis proves useful in recovering object 99208.
    
    Regards,
        Cees
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