NROL-27 pre-launch elements

From: Ted Molczan (ssl3molcz@rogers.com)
Date: Fri Mar 11 2011 - 04:52:55 UTC

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    NROL-27 is scheduled for launch from Cape Canaveral on a Delta 4 Medium, with a 4 m dia fairing and two solid rocket boosters, on
    2011 Mar 11, between 22:57 UTC and 23:38 UTC. The launch azimuth indicates that the final orbit will be geosynchronous. 
    
    I suspect that the payload is an SDS (Satellite Data System) communications satellite. The main purpose of the SDS satellites is to
    relay data in real-time from the four KeyHole imagery intelligence satellites that operate in low Earth orbit, directly to NRO
    receiving stations in the U.S.A. The primary SDS constellation consists of two satellites in Molniya orbit and two in GEO. They are
    often augmented by older spacecraft that remain operational years after their replacements have been launched.
    
    The existing primary GEO SDS spacecraft were launched in 2000 and 2001, and probably are about due for replacement. They are located
    at 10 W and 144 W
    
    NROL-27's exact route to GEO is unknown. I offer the following notional elements, based on launch at the start of the window, and a
    descending node burn to GTO (geostationary transfer orbit), but the actual orbit is likely to be somewhat different.
    
                                                           278 X 36398 km
    1 71502U          11071.18212730  .00000000  00000-0  00000-0 0    02
    2 71502  27.2800 331.4161 7307000 182.9000 167.5000  2.23480000    00
    
    NROL-27 is unlikely to be spotted in GTO, but should not be difficult to find if/when it arrives at either 10 W or 144 W. Its
    initial operational inclination is likely to be about 4 deg.
    
    Happy hunting!
    Ted Molczan
    
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