Re: Decay alert : 29058 Object B

From: Fco. Javier Iruretagoyena (Webmail) (
Date: Thu Apr 27 2006 - 03:20:43 EDT

  • Next message: Russell Eberst: "2006APR26-27.OBS"

    Does anyone know if object 29058 has decayed already?
    Zaragoza, Spain
    ---- "Björn Gimle" <> escribió: 
    > Current Space-Track elements seem to show this bottoming out at 138 km
    > altitude  at about 15°N, 108°W at 23:43 UT this evening, shortly before
    > making a southerly pass at my 20 (Toronto, 43°N 79°W).
    > Is a perigee of 138 km terminally low?
    That depends more on the area/mass ratio of the object (roughly proportional
    to B* (col.55-61 of line1) and excentricity of the orbit (col.27-33 of
    For a Molniya type orbit (high excentricity) a perigee of  75 km is not
    immediately fatal (it will be glowing red after perigee, and lose its solar
    For a circular orbit and "normal" density I consider a mean motion of 16.55
    as fatal - this corresponds to perigee=apogee=125 km.
    But for any near-circular orbit I use the ndot2 value (col.35-43 of line1)
    as a rule-of-thumb: divide 0.06 by ndot2 to get remaining days. I have one
    elset with ndot2 ~0.20 at ~06116.86 which would mean decay ~06117.19
    An even better way is to plot 1/ndot2 for several recent elsets.
    ndot2 tripled between 06116.50 and 06116.86, which would make ndot2 infinite
    after about half that interval, at 06117.04
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