Brightness of Misty 1

From: Ted Molczan (seesat@rogers.com)
Date: Sat Nov 19 2005 - 19:18:52 EST

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    I have analyzed brightness observations of Misty 1 (aka 90019B / 20516 / USA 53
    / AFP-731), and compared them with those of the KeyHole satellites.
    
    The results are in the form of plots of magnitude normalized to 1000 km range vs
    phase angle.
    
    Here is a plot of all 38 brightness observations of Misty 1 known to me:
    
    http://satobs.org/seesat_ref/Misty1/90019B_mag.jpg
    
    The data is categorized according to Misty 1's three known orbits (typical
    elsets are appended).
    
    The yellow symbols denote observations of Misty 1 in its 62 deg inclination, 250
    km parking orbit. Russell Eberst made three of the observations; an observer in
    Yellowknife (capital city of Canada's Northwest Territories) made the other
    three.
    
    The red symbols denote observations of Misty 1 in its 65 deg inclination, 800 km
    orbit. Russell Eberst and Pierre Neirinck made nearly all of the observations
    during 1990 Jun and Oct-Nov. An Australian observer made one observation in 1990
    Mar.
    
    The blue symbols denote observations of Misty 1 in its 66.2 deg inclination, 728
    km orbit. Russell Eberst made all five observations during 1996-97, which he
    reported as three different unknowns, and which I identified in 2000.
    
    It is very unusual to find such a wide range of brightness and poor correlation
    with phase angle, over so small a number of observations.
    
    Since Misty 1 is thought to be a stealthy version of a KeyHole, I have produced
    a couple of comparison plots.
    
    The first one compares Misty 1 with three older KeyHoles: 84122A / 15423, 87090A
    / 18441 and 88099A / 19625. All three KeyHoles had similar optical
    characteristics to one another:
    
    http://satobs.org/seesat_ref/Misty1/90019B_mag_vs_old_KH.jpg
    
    The second one compares Misty 1 with three newer KeyHoles: 92083A / 22251,
    95066A / 23728 and 96072A / 24680. All three KeyHoles had similar optical
    characteristics to one another:
    
    http://satobs.org/seesat_ref/Misty1/90019B_mag_vs_new_KH.jpg
    
    I suspect that Misty 1 is most like the newer KeyHoles. Both were originally
    designed for shuttle-launch, and both almost certainly were built around
    Lockheed's satellite Bus-1, as Charles Vick figured out quite a few years ago.
    Misty 1's total mass and known/assumed manoeuvres would have required most of
    Bus-1's maximum propellant load of 11,660 lbm, which far exceeded that of
    earlier KeyHole buses.
    
    The main difference between the plots is that the newer Bus-1 KeyHoles are about
    1 mag fainter than the older ones. 
    
    In both plots, Misty 1's extremes of brightness are similar to those of the
    KeyHoles, but the KeyHoles reached such extremes relatively rarely.
    
    Ted Molczan
    
    
    Elements of Misty 1 derived from hobbyist observations:
    
    1990 Mar 02 - 07                                         256 X 257 km
    1 20516U 90019B   90 63.25371956  .00185604  00000-0  25000-3 0    06
    2 20516  61.9930 163.5307 0001000 267.0000 184.4500 16.06000000    00
    
    1990 Mar 07 - Nov 07                                     791 X 815 km
    1 20516U 90019B   90169.96472801  .00000241  00000-0  10000-3 0    09
    2 20516  65.0194 222.8464 0016600 348.2506  11.8204 14.26226467    06
                                                             791 X 814 km
    1 20516U 90019B   90299.82375579  .00000277  00000-0  11483-3 0    07
    2 20516  65.0194 222.4319 0016320 301.3908  58.5348 14.26287908    00
    
    1990 Nov 07 - ???                                        724 X 732 km
    1 20516U 90019B   97284.23458324  .00000027  00000-0  70436-5 0    01
    2 20516  66.1631  65.2852 0005248 187.8717 231.2307 14.48751217    03
    
    
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