USA 193 elements from observations

From: Ted Molczan (
Date: Thu Dec 21 2006 - 13:28:53 EST

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    USA 193          5.0  2.5  0.0  3.5 v
    1 29651U 06057A   06355.22183776  .00018290  00000-0  15062-3 0    06
    2 29651  58.5011  93.0029 0009703  91.7888 268.4308 15.69797969    07
    Arc 2006 Dec 16.27 - 21.24, WRMS residuals = 0.034 deg
    The payload fairing was the Delta 2's 3 m diameter of standard length, so the
    satellite bus should not be much larger than about 5 m x 2.5 m, which typically
    would predict a standard magnitude of about 5 or 6 (1000 km, 90 deg phase
    angle), but it is quite a bit brighter, with std mag near mag 3.5:
    The brightness varies considerably for a given phase angle, which suggests to me
    a complex shape, probably due to large, reflective panels. For this reason, I
    suspect it is more likely a radar than an optical imager.
    The std mag is similar to that of Japan's IGS 1B radar imager, but over many
    observations the IGS appears to be a bit less variable for a given phase angle:
    It will be interesting to see how they compare once there are a comparable
    number of 06057A observations.
    Also, we should watch the evolution of the elements to see whether or not the
    orbit turns out to be frozen; if so, then its argument of perigee will never
    stray far from 90 deg. Frozen orbits were employed for the first four Lacrosses,
    and Seasat 1, which are radar imaging satellites.
    Ted Molczan
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