USA 193 debris situation

From: Ted Molczan (
Date: Sun Mar 02 2008 - 15:26:05 UTC

  • Next message: Robert Holdsworth: "Re: USA 193 debris situation"

    Of the less than 3,000 fragments of USA 193 reportedly detected by US STRATCOM,
    the vast majority should have decayed within hours or a few days of the
    intercept on 2008 Feb 21 UTC. To my knowledge, the total number remaining in
    orbit has not been published; my guess is that it does not exceed a few hundred,
    and could well be much less.
    Dr. T.S. Kelso has made decay predictions, as plotted near the bottom of the
    following page:
    Dr. Kelso's 20 cm plot is similar to results I have obtained using Satevo v0.51.
    Basically, most of the remaining debris will decay by the end of March.
    As far as I can tell, the debris situation is unfolding much as I described soon
    after plans to intercept USA 193 were announced:
    As has been reported on the list, NROL-28 is being delayed due to concerns about
    the USA 193 debris. This was the NRO's statement, issued on Feb 27:
    "The NRO will postpone its launch of mission NROL-28 approximately two weeks as
    a precautionary move to avoid possible debris from the NRO experimental
    satellite which was intercepted last Wednesday, 20 Feb 2008. When established,
    the revised date will be posted."
    Some may see this as an indication that the orbital debris situation is more
    severe than the public is being told; however, my intuition is that it is simply
    caution on the part of those managing the launch. As shown in Dr. Kelso's
    analysis, at least half of the debris now in orbit will decay within two weeks.
    Also, the remaining debris will have spread out over a planar swath some 2.5
    times wider than at present. So, there would much less debris, spread much more
    Another possibility is that it was taking longer than expected to complete the
    orbital analysis of the USA 193 debris, resulting in less complete and/or
    confident collision-avoidance analyses than required, hence the decision to
    delay the launch.
    The delay may seem overly cautious, given the small number of fragments likely
    remaining in orbit, but not unusually so, given the well known phenomenon of
    bureaucratic CYA. Absent strong evidence to the contrary, I prefer this
    interpretation over more dramatic ones.
    Ted Molczan
    Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive:

    This archive was generated by hypermail 2b29 : Sun Mar 02 2008 - 15:26:42 UTC