VAFB Atlas 2AS NOSS search elements

From: Ted Molczan (
Date: Sat Nov 29 2003 - 11:01:52 EST

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    1. Launch
    The NOTAM has been issued for the Atlas 2AS launch of a NOSS payload from VAFB,
    scheduled for 2003 Dec 02 UTC:
    3437N/12037W 3438N/12033W WITHIN AN AREA BNDD BY 3242N/12001W 3318N/12016W
    3326N/11948W 3250N/11933W SFC UNL 02 DEC 09:48 UNTIL 02 DEC 10:53
    As expected, the co-ordinates are nearly identical to those of the NOTAM of the
    similar launch on 2001 Sep 08 UTC.
    Until now, the launch period has been stated as 09:00 - 13:00 UTC. The NOTAM
    narrows this to 09:48 - 10:53 UTC, which is consistent with a recent rumour of
    lift-off at 10:03 UTC.
    These are the expected initial orbits after launch:
    T+00:10:36.7  Centaur MECO 1, 62.3 deg,  160 km x 1206 km (parking orbit)
    T+01:02:29.4  Centaur MECO 2, 63.4 deg, 1007 km x 1208 km (final orbit)
    The second Centaur burn, occurs at the first apogee, near the equator, roughly
    circularizing the orbit and adjusting its inclination to 63.4 deg.
    In the event of a launch delay, lift-off will advance 13.98 min per day, due to
    the precession of the target plane relative Earth's surface.
    2. Visibility Windows
    Assuming the rumoured 10:03 UTC lift-off time is correct, most Northern
    Hemisphere observers will have evening visibility, and Southern Hemisphere
    observers will have morning visibility.
    3. Search Elements
    Assuming the rumoured 10:03 UTC lift-off time is correct, and that this is a
    carbon-copy of the 2001 launch, then based upon hobbyist tracking following that
    launch, these will be the orbits of the various pieces at the second ascending
    Centaur         10.1  3.0  0.0  3.7 v                      991 X 1214
    1 71004U          03336.53777889  .00000000  00000-0  00000-0 0    04
    2 71004  63.4733 300.6384 0149592 188.4793 171.3703 13.43448178    09
    NOSS leader      0.0  0.0  0.0  4.9 v                     1007 X 1209
    1 71001U          03336.53798225  .00000000  00000-0  00000-0 0    08
    2 71001  63.4247 301.3282 0135067 185.2161 174.7465 13.42002823    01
    NOSS trailer     0.0  0.0  0.0  4.9 v                     1007 X 1210
    1 71002U          03336.53799524  .00000000  00000-0  00000-0 0    02
    2 71002  63.4241 301.3249 0135680 184.7387 175.2364 13.41930476    01
    The Centaur will have burned off its remaining propellant, with most of the
    velocity change having gone into shifting its plane about 0.7 deg west of the
    payloads' plane.
    The payloads will trail the Centaur in their slightly higher orbits. 
    The big question is how many payloads? 
    In a post that will follow this one, I will explain why I believe that this time
    there will be three payloads, but we can be fairly certain that there will be at
    least the above two, which I have dubbed NOSS leader and NOSS trailer, in
    accordance with our hobbyist convention.
    Here is a tabulation of the spacing of the objects at the epoch of above orbits,
    in seconds of time relative the Centaur:
     Piece       T + Centaur (s)
    ---------    ---------------
    Centaur            0.0
    NOSS leader       17.6
    NOSS trailer      18.7
    The NOSS leader will fall further behind the Centaur at the rate of about 6.9 s
    per rev, or 93 s per day.
    The NOSS trailer will fall further behind the NOSS leader at the rate of about
    0.35 s per rev, or 4.7 s per day.
    If the third NOSS appears, then I expect it to be very near the above two,
    perhaps initially about 1 s in front or behind.
    In that case, we will have to revise the naming to perhaps, leader, trailer1 and
    Through a series of manoeuvres, over a period of weeks, more likely months, two
    NOSS will end up in one plane as leader and trailer, and the other will end up
    as the outlier, about 0.2 deg away in plane.
    The search elements should be accurate to within about one minute on launch day,
    but it would be wise to start looking a couple of minutes early.
    Happy hunting!
    Ted Molczan
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