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 ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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