Pleiades 1B recovered

From: C. Bassa (
Date: Sat Mar 30 2013 - 22:03:24 UTC

  • Next message: tom: "Help with identification"

    Pleiades 1B [39019/12068A] is an Earth imaging satellite and was
    launched on December 2, 2012 from Kourou, French Guiana. Its orbital
    elements are not published by SpaceTrack, probably because it serves
    both military as well as civilian users.
    It has been reported that Pleiades 1B shares the same sun-synchronous
    orbit as Pleiades 1A [38012/11076F] and that they are phased 180
    degrees apart: Since
    SpaceTrack does publish the elements of Pleiades 1A it is quite easy
    to estimate the elements of Pleiades 1B.
    It turns out that the 99043 unknown that I observed on March 13
    ( matches the expected
    orbit of Pleiades 1B. Based on the orbital estimates I and Ted
    suggested I was able to reobserve it again earlier this evening and
    obtained these two measurements:
    99043 13 572A   4553 E 20130330213646048 17 25 1429212+723311 37 S
    99043 13 572A   4553 E 20130330213653828 17 25 1506486+752004 37 S
    Combined with the March 13 observations
    99043 13 572A   4553 E 20130313212012891 17 25 2009768+572820 37 S
    99043 13 572A   4553 E 20130313212019851 17 25 2016667+563663 37 S
    I estimate the following circular search orbit:
    1 99043U          13089.90057799  .00000000  00000-0  50000-3 0    03
    2 99043  98.2045 166.2406 0000000   0.0000  57.5005 14.58593206    05
    This orbit matches the Pleiades 1A orbit quite well and is indeed
    exactly 180 degrees phased. The predicted time should probably be
    within one or two minutes per day since the epoch. I leave it for Ted
    and Mike to provide a proper search orbit and also to confirm my
    identification. I estimate it at a brightness of about magnitude 5 so
    it should be quite easy to reobserve.
    Because Pleiades 1A was launched together with the Elisa quartet, the
    March 13 observations matched that orbital plane best, hence Ted
    suggestion that it was Elisa W11 or Elisa W23. It had nagged me that
    the 99043 unknown seemed too bright to be an Elisa object and I
    wondered why I had only seen one...
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