RE: X-37B OTV-1 - circumstances of orbit-raising of Aug 09

From: Derek C Breit (
Date: Wed Aug 25 2010 - 04:55:33 UTC

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    -----Original Message-----
    [] On Behalf
    Of Ted Molczan
    Sent: Tuesday, August 24, 2010 9:09 PM
    Subject: X-37B OTV-1 - circumstances of orbit-raising of Aug 09
    Leonard David has nicely documented X-37B OTV-1's orbit-raising of Aug 9,
    including the involvement of several SeeSat-L members in the subsequent
    tracking and orbit analysis:
    One of the findings reported in the article is the apparent timing of the
    two orbit-raising manoeuvres to enable nearly continuous monitoring by
    several Air Force Satellite Control Network
    (AFSCN) tracking stations. Since that fact may be useful in understanding
    future manoeuvres, I want to provide some technical details that are not
    appropriate for a news article, but well-suited to this forum.
    Propagating the new orbit backward to the time of its closest separation
    from the original orbit, revealed the mid-point between the manoeuvres,
    which were performed on opposite sides of the Earth, near a perigee and an
    The first manoeuvre occurred on Aug 09, about 17:12 UTC, near 40 S, 98 E.
    The spacecraft was near the apogee of its original 403 X 420 km orbit, and
    manoeuvred to raise its perigee by 42 km, resulting in a 420 X 445 km orbit.
    Since the new perigee was greater than the original apogee, the line of
    apsides was effectively rotated 180 deg. 
    About 16 minutes later, the spacecraft came within range of the Air Force
    Satellite Control Network
    (AFSCN) tracking station at Hawaii, the first of five AFSCN stations in a
    position to monitor it throughout the remainder of the manoeuvre sequence. 
    The final manoeuvre occurred half an orbit after the first one, near the new
    apogee, at about 17:58 UTC, near 40 N, 100 W. The perigee was raised 12 km,
    resulting in a 432 x 445 km orbit. This was just before LOS by the AFSCN
    station at VAFB, and well above the horizon of the Colorado AFSCN station.
    Depending on the duration of the burn, the New Hampshire station may also
    have been able to monitor it directly; it certainly would have been able to
    monitor the results.
    Below are the estimated AOS/LOS times of the AFSCN tracking stations that
    OTV-1 passed during the manoeuvre sequence:
       AOS        LOS
    17:38:28 - 17:48:29  AFSCN Hawaii Tracking Station, Kaena Point, Oahu,
    Hawaii 17:40:14 - 17:49:36  AFSCN Guam Tracking Station, Andersen AFB, Guam
    17:47:42 - 17:58:13  AFSCN Vandenberg Tracking Station, Vandenberg AFB,
    California 17:51:24 - 18:01:56  AFSCN Colorado Tracking Station, Schriever
    AFB, Colorado 17:58:15 - 18:08:31  AFSCN New Hampshire Tracking Station, New
    Boston Air Station, New Hampshire
    AOS and LOS correspond to estimated time of rise/set, 2 deg above the
    horizon; actual AOS/LOS depend on local terrain, not considered in this
    Below are elsets documenting the manoeuvre. The pre-manoeuvre elset is
    derived from our last observations of the original orbit, on July 29. The
    two manoeuvre elsets are accurate estimates; their epochs correspond to the
    manoeuvre times.
    Pre-manoeuvre orbit                                      403 X 420 km
    1 36514U 10015A   10210.09309780  .00000000  00000-0  00000-0 0    09
    2 36514  39.9851 119.3456 0012533 356.3806   3.6913 15.52766118    04
    First manoeuvre                                          420 X 445 km
    1 36514U 10015A   10221.71696759  .00000000  00000-0  00000-0 0    05
    2 36514  39.9851  47.8421 0018773 266.6117   0.6500 15.45484000    09
    Final manoeuvre                                          432 X 445 km
    1 36514U 10015A   10221.74841435  .00000000  00000-0  00000-0 0    01
    2 36514  39.9851  47.6508 0009598 266.8531 175.6000 15.43360000    09
    Ted Molczan
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