RE: OPS 8180 (RADCAT) 1972-076A

From: Ted Molczan (ssl3molcz@rogers.com)
Date: Fri Aug 06 2010 - 15:29:19 UTC

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    Brian Webb asked:
    
    > I have two questions about OPS 8180 (RADCAT) 1972-076A:
    > 
    > 1. When this spacecraft was launched in 1972, was there any information
    > publicly available about it? What did the TRW Space Log say about it? 
    
    I do not know how much information was made public in 1972; the 1987 edition of the TRW Space Log
    does not name or describe the object.
    
    > I have the impression that it was an unclassified payload with a highly
    > specialized purpose that would not have been of much interest to the public.
    
    I agree; it is a radar calibration target.
    
    Two Radcats were built; the first one was lost (along with many other payloads) in a launch failure
    on 1968 Aug 16 UTC; see Jonathan McDowell's launch log for details:
    
    http://www.planet4589.org/space/log/launch.html
    
    The second one was launched on 1972 Oct 02 UTC. USSTRATCOM's catalogue number is 6212. The COSPAR
    designation is 1972-076A. 
    
    > 2. Are there any detailed drawings or photos of this satellite available on the Internet?
    
    A drawing appears in the 1971 report, "RADCAT Radar Measurement Program", available here, scanned
    into a 26 MB pdf:
    
    http://handle.dtic.mil/100.2/ADA036305
    
    The drawing is in Figure E-1 on page 241 of the pdf, which I have extracted and provided below: 
    
    http://satobs.org/seesat_ref/misc/72076A_dwg.jpg
    
    On pg. 240 of the pdf, Radcat is described as, "an 8 foot cylinder with 2:1 oblate spheroidal ends".
    Based on the dimensions given in Figure E-1, its overall length is 10 ft (3.05 m), and its diameter
    is 4 ft (1.22 m).
    
    NOTE: The SI dimensions derived from the report, solve a long-standing problem in the R.A.E. Table
    of Earth Satellites 1957-1989, which describes Radcat as a cylinder, 12.2 m long and 3.05 m in
    diameter. Those dimensions never made sense, and now it is obvious that they arose from some sort of
    garbling of information, whereby 10 times the diameter became the length, and the length became the
    diameter.
    
    Observed Optical Characteristics
    
    Russell Eberst has reported 57 observations of Radcat since my correspondence with him began, in
    1989, which I have used to determine its standard visual magnitude, per the following plot of
    magnitude normalized to 1000 km range vs. phase angle:
    
    http://satobs.org/seesat_ref/misc/72076A_std_mag.pdf
    
    The standard magnitude is 5.7 +/- 1 (1000 km, 90 deg phase angle). Coefficient of phase is 0.017
    mag/deg.
    
    In its present 470 km circular orbit, the object reaches magnitude 3.7 +/- 1 when observed at high
    elevation, and well illuminated.
    
    The object was steady in brightness in each one of Russell's 57 observations. The PPAS record of 18
    observations, which spans 1973-2005, is in agreement. The PPAS archive is available here:
    
    http://www.io.com/~mmccants/bwgs/index.html
    
    Ted Molczan
    
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