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Re: {MPML} Herschel/Planck objects

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  • dfischer@astro.uni-bonn.de
    ... THE ASTRONOMER Electronic Circular No 2553 2009 May 24 11.47UT ... PHOTOMETRY OF OBJECTS IN THE HERSCHEL-PLANCK LAUNCH CONSTELLATION 1212 observations
    Message 1 of 6 , May 24, 2009
      Of some interest in the context of the Herschel/Planck "UFOs":

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      THE ASTRONOMER Electronic Circular No 2553 2009 May 24 11.47UT
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      PHOTOMETRY OF OBJECTS IN THE HERSCHEL-PLANCK LAUNCH CONSTELLATION
      1212 observations of objects that for the Herschel-Planck launch cluster
      up to May 21.35 have been reported on DASO Circulars #213-230. Initially
      there was some confusion about the precise identity of each the objects,
      firm identifications have now been published on DASO #226
      (http://www.cfa.harvard.edu/~gwilliams/DASO/000000/DASO_000226.txt) The
      four brightest objects in the constellation are the Ariane upper stage
      and, forming a tight cluster about a third of a degree away, Herschel,
      Planck and the Sylda support that covered Planck during launch. Other,
      fainter, objects of uncertain identification, designated 2009-026E and
      2009-02F, have been sighted around the Ariane upper stage: the latter
      has a large non-gravitational component of motion and has been shown to
      have separated from the Ariane upper stage shortly after launch.
      The photometry has been converted to R assuming a solar colour index of
      V-R=+0.53 and that unfiltered photometry is equivalent to R.
      Identifications and absolute magnitudes are in the table:
      Provisional Formal Absolute
      Designation Identification Designation magnitude Notes
      HP03 Ariane upper stage 2009-026C 28.7
      Planck Planck Planck 29.2
      HP02 Herschel Herschel 28.8
      HP01 Sylda 2009-026D 30.3
      HP04 Unidentified 2009-026E 30.7 Fading
      HP05 Unidentified 2009-026F 31.4 Fading

      Planck, the upper stage, the Sylda and, apart from one excursion in
      brightness that may have been due either to a small change of aspect
      angle, or to wrongly identified observations, Herschel, all show good
      fits to a pure reflection light curve of constant absolute magnitude. In
      contrast, 2009-026E and 2009-026F show a persistent fade consistent with
      a cross-section that has decreased in diameter by a factor of 2. Light
      curves for these objects can be found at the url:
      http://www.observadores-cometas.com/Herschel/Image_of_the_day/HER04_05-09
      0522.jpg and an image archive at
      http://www.observadores-cometas.com/Herschel/images/images.htm

      The strong non-gravitational motion of 2009-026F and the fact that it
      separated from the Ariane upper stage shortly after launch suggest that
      this may be an object of low mass and large surface area, with high
      albedo, however the fading appears inconsistent with a refractory nature
      (such as shed insulation) unless there is a slow aspect angle change
      with time, something not seen in the upper stage or the Sylda.

      Herschel commissioning is proceeding extremely smoothly. The satellite
      is in excellent health and the four days of check-out observations have
      already been made. Real-time updates on the progress of Herschel testing
      can be obtained from the Herschel Twitter account (http://twitter.com/),
      ESAHerschel. The Herschel Team is buoyant at the tremendously successful
      progress to date and the success of the commissioning activities
      carried-out so far.
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      (This is a paid-subscription-only electronic newsletter but given the intense
      work many on MPML have put into following the HP aftermath, re-distributing
      it "for scholarly use only" here seems more than fair. Comments welcome!)

      Dan
    • Brian Skiff
      ... It may not matter much given the likely uncertainties involved, but this solar V-R color is for the old Johnson V-Rj system, which almost certainly no one
      Message 2 of 6 , May 24, 2009
        > The photometry has been converted to R assuming a solar colour index of
        > V-R=+0.53 and that unfiltered photometry is equivalent to R.


        It may not matter much given the likely uncertainties involved,
        but this solar V-R color is for the old Johnson V-Rj system, which
        almost certainly no one uses. Cousins V-R for the Sun is something
        close to 0.36 +/- 0.01 or so.


        \Brian
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