RE: NROL-24 observations by Richard Miles; payload elset

From: Bob Christy (rdc@zarya.info)
Date: Wed Dec 12 2007 - 00:08:34 UTC

  • Next message: Ted Molczan: "Updated NROL-24 elements"

    NROL-24 is aimed at the gap between USA-137 (90025) and USA-179 (90027)
    created by removal of USA-125 (90028) from the constellation. It is the two
    other satellites that should be used as yardsticks to measure NROL-24's
    place.
    
    Using data from the latest available element sets for USA-137, USA-179 and
    NROL-24, the orbit planes on Dec 17 (one week after the latest launch) will
    be (+/-1 degree):
       USA-137   190 deg
       USA-179    76 deg
       NROL-24   315 deg
    
    The three plane separations will be:
       114 deg (USA-137 to USA-179 - already exists)
       121 deg (USA-179 to NROL-24)
       125 deg (NROL-24 to USA-137)
    
    NROL-24 is an almost-ideal fit with USA-179, its immediate predecessor.
    USA-137 (already on orbit) is the 'rogue', being 'out of place' by about
    five degrees.
    
    Precise 120 degree separation is desirable but not crucial because, with
    three satellites, there is much overlap in Earth coverage. For a while,
    until early-2007, one of the SDS functions was being provided from only two
    satellites and was still achieving 20+ hours per day coverage.
    
    There is evidence that USA-125 is being run down. One of its communications
    payloads ceased providing service 2007 October 15, and the de-spin mechanism
    of its aerial array appears to be longer functioning.
    
    Bob Christy
    
    
    
    
    
    > -----Original Message-----
    > From: Ted Molczan [mailto:ssl2molcz@rogers.com] 
    > Sent: Tuesday, December 11, 2007 10:44 PM
    > To: seesat-l@satobs.org
    > Subject: NROL-24 observations by Richard Miles; payload elset
    > 
    
    
    ...................................The initial orbital plane is about 16 deg
    east of the 90028 / 
    > 04846A Molniya object that I and others expected NROL-24 to 
    > target for replacement. I am surprised to see such a wide 
    > planar separation, so perhaps the 90028 replacement theory 
    > needs to be reconsidered. Note that due to their different 
    > rates of precession, NROL-24 would overtake the plane of 
    > 90028 in about 41 days, but that seems a long time to wait in 
    > the intermediate orbit. Perhaps the plane will be shifted 
    > west as part of the manoeuvres to Molniya; I have not 
    > analysed this possibility.
    > 
    > Ted Molczan
    > 
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