RE: NOSS

From: Ted Molczan (molczan@rogers.com)
Date: Fri Apr 05 2002 - 05:46:24 EST

  • Next message: Bill_T_Bard@raytheon.com: "Re: Interesting unid(s)"

    Sue Wheatley asked:
    
    > Tonight I saw two objects about 2 degrees apart, traveling in 
    > the same line. The trailing object flared for about 8 seconds 
    > to a -4 or brighter, and then dimmed to match the magnitude 
    > of the first (about 3rd mag). Did I see USA 160?
    
    The visual appearance you observed is consistent with other recent
    reports that have been posted here, so my guess is that you did see USA
    160 and its companion. If you can provide the date, time and a rough
    position or track, I could be more certain.
    
    >  And if so, was the first member of the duo a satellite or debris?
    
    Two payloads appeared shortly after launch on 2001 Sep 08, and have been
    tracked ever since. We know they are payloads because both have
    manoeuvred.
    
    Thus far, only three pieces have been officially catalogued, only one of
    which is a payload:
    
    2001-040A    26905  USA 160
    2001-040B    26906  ATLAS 2AS CENTAUR R/B 
    2001-040C    26907  USA 160 DEB
    
    Hobbyists are routinely tracking the Centaur plus two payloads. We have
    not detected any other objects in or near the orbital plane.
    
    Until the situation becomes clearer, we have assigned one of the
    payloads to the 26907 catalogue number, which officially is debris.
    
    Every one of the first and second generation NOSS triad members shed a
    small piece of debris at the time of deployment that is too faint to be
    tracked with binoculars. So it is quite possible that 26907 actually is
    debris. If not, then perhaps the catalogue entry is erroneous and it
    really is one of the two payloads.
    
    The two payloads appear to be about as bright as the second generation
    NOSS, and they behave similarly in that most of the time they are around
    magnitude 5 or 6 at best, but occasionally brighten to magnitude 3 or 4.
    The recent flaring is less common, but has been observed, as I pointed
    out in an earlier message.
    
    The big mystery is the absence of a third payload to complete the
    standard NOSS triad. Second generation NOSS deployments typically took
    about 28 days. The triad members were carried on a manoeuvrable payload
    dispenser, which placed them in the exact orbits required to form the
    familiar "flying triangle".
    
    The 01040A launch almost certainly did not involve the use of a payload
    carrier. The payloads seem to have been deployed separately from the
    Centaur. Alternatively, they could have been joined together at
    separation from the Centaur, and subsequently separated from one
    another.
    
    For the first couple of months or so, both payloads remained in about
    the same plane, but made numerous small manoeuvres, such that at times
    they drifted apart and at other times they station-kept at a variety of
    distances, often much farther apart than standard NOSS. Eventually, they
    manoeuvred to the present close separation, and adjusted their
    inclination slightly, such that their ascending nodes no longer
    precessed at the identical rate, thus causing them to drift apart. Once
    they reached the present separation, about 0.24 deg, one or both
    manoeuvred to equalize their precession rates.
    
    The present planar and along-track separation is close to that of an
    operational NOSS triad, but without the third member.
    
    It has been my guess that the third member is attached to one of the two
    payloads, awaiting deployment at some time. I am increasingly doubtful
    of that possibility, because it seems that the opportune time to deploy
    the third member arose weeks ago, when their planar separation was
    stabilized.
    
    Perhaps there are other conditions that must be met for the third
    payload to be deployed. Or, it may be that only two payloads were
    launched. That seems unlikely, because the relative position of the two
    payloads looks like too much like a normal triad with one member
    missing.
    
    Another possibility, which I am increasingly leaning toward, is that
    three payloads were launched, but that one failed to separate and is a
    write-off.
    
    That could explain the couple of months of frequent manoeuvring -
    perhaps engineers were evaluating novel operating modes in an effort to
    salvage as much of the designed operational capability as possible.
    These objects are widely believed to track the positions of ships at sea
    by triangulating on their radio transmissions. (This is a surveillance
    mission, not a navigation mission.)
    
    My guess is that the novel operating modes did not sufficiently improve
    the quality of the data, so the operators decided to proceed to
    manoeuvre the objects to something like the standard relative positions.
    One reason for doing so might be that they have accumulated considerable
    experience over the years in working around the failure of a single
    triad member, which provides the most confident basis for making the
    best of the present situation.
    
    Another Atlas 2AS launch is scheduled for launch from VAFB in 2002
    November, which I suspect carries the same payloads as the 01040A Atlas
    2AS. That should settle the present mystery. If we see a repeat
    performance, then most likely it was always intended to change from a
    NOSS triad to a doublet. If a triad is launched, then that will almost
    certainly confirm that one of the 01040A's payloads failed to separate.
    
    Ted Molczan
    
    
    
    
    
    
    
    
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