RE: Viewing circumstances for Endeavour & ISS

From: CmdrJaycee@aol.com
Date: Sun May 15 2011 - 16:52:39 UTC

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    In a message dated 5/15/11 8:00:09 AM, Ted Molczan writes:
    
    > On the New York pass of May 30, at 04:48 EDT, the immediate 
    > post-undocking TLE and the TLE after final separation are 1.5 km apart, almost entirely 
    > in altitude above the Earth. At culmination, that would result in a 
    > difference inelevation above the horizon of about 0.11 deg.
    > 
    
    That is just about where the Sensor Test for Orion Relative Navigation Risk 
    Mitigation (STORRM) Apollo-style rendezvous test puts Endeavour at its 
    closest approach -- about 1000 feet below and 300 feet behind the ISS, just 
    prior to the third and final separation burn, which is scheduled to occur just 
    ten minutes or so before the 30 May pass as seen from New York.   See: 
    
    http://spaceflightnow.com/shuttle/sts134/110421storrm/
    
    I should note that this article was written assuming an April 29 launch 
    date.   Also, it notes the distance at closest approach during the STORRM 
    maneuvers to 1000 feet behind and 300 feet below.   This appears to have 
    mistakenly reversed the distances.   Both the NASA STS-134 press kit (Page 7)--
    
    http://www.nasa.gov/pdf/538352main_sts134_presskit_508.pdf
    
    as well as the "STS-134: Legacy of Endeavour" mission overview video (at 
    about the 8:20 mark): 
    
    http://www.youtube.com/watch?v=n3xWRE2OfH4
    
    indicate Endeavour's closest STORRM approach to the ISS to be 1000 feet 
    below (1044 feet below is cited in the video) and 300 feet behind the ISS. (The 
    press kit, Page 7, also indicates Endeavour "will approach no closer than 
    600 feet to the station.")
    
    I recall the third and final separation burn was described as returning the 
    shuttle to a normal separation in preparation for reentry, but I can't 
    recall the source for that.   If so, with recent past missions, the shuttle 
    gradually pulls away in front of the ISS.   So, by the time the pass as visible 
    in New York occurs 10 minutes or so after the final separation burn, that 
    "300 feet behind" will have closed a bit, perhaps making them appear almost 
    vertically stacked when seen at highest elevation.   
    
    To illustrate, I loaded the following TLEs Ted provided into Starry Night 
    Pro:
    
    > I also considered the immediate post-undocking TLE:
    > 
    > 1 00134U          11150.16593341  .00020000  00000-0  20000-3 0  9221
    > 2 00134  51.6467 253.0815 0004948 342.4954  17.6039 15.75906166  2160
    > 
    > Here is the TLE after the final separation:
    > 
    > 1 00134U          11150.41955913  .00020000  00000-0  20000-3 0  9282
    > 2 00134  51.6442 251.7701 0002335 345.7065  14.4033 15.76536145  2200
    > 
    
    Starry Night Pro, indeed, places Endeavour almost directly below the ISS at 
    the peak of the pass, separated by a gap of 7 minutes of arc.   For 
    comparison, the gap between Alcor and Mizar in the Dipper's handle (which they 
    conveniently pass above) is a bit less than 12 minutes of arc.   Here's a 
    screenshot of the Starry Night Pro display (ISS immediate postdocking = 
    "ISS-1341stPD"; Endeavour third separation burn = "STS134 SB3"):
    
    http://www.jacook.name/sats/STS134-ISS_30May2011_NY.png
    
    (Also not shown with my current Starry Night Pro default magnitude 
    settings, both the ISS and Endeavour should appear much brighter than Mizar.)
    
    Still, all this presumes an on time launch, a nominal mission, and a STORRM 
    test conducted on time -- and, of course, clear skies.   We'll get a better 
    sense in a few days once the projected ISS TLEs for 29 and 30 May are made 
    available. 
    
    http://spaceflight.nasa.gov/realdata/sightings/SSapplications/Post/JavaSSOP/
    orbit/ISS/SVPOST.html
    
    As of now, they only go out to 27 May.   But keep in mind, this STORRM 
    maneuver has a very tight timeline prior to the 30 May NY pass.   If undocking 
    is late or they pause the STORMM firings for some reason, things could change 
    quite a bit.
    
    Jim Cook
    Germantown, MD
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