Stardust flyby

From: richard.keen@kingsmarket.com
Date: Fri Jan 12 2001 - 18:31:57 PST

  • Next message: Tony Beresford: "Re: Stardust flyby"

                                      
      Hi all -
      I got this message (only very slightly edited) from David Dunham via the IOTA
    (International Occultation Timing Association) mailing list, and it's his
    opinion that there may be a chance of seeing the Stardust flyby with moderately
    sized telescopes.
     Cheers, Rich Keen, Coal Creek Canyon, Colorado, USA (39.877N, 105.391W,
    elevation 2728m)
      P.S. - could someone be kind enough to run predictions for my location, using
    the JPL Horizons programs described in the message below?  I don't have web
    access until Tuesday.
      thanks....
    
    Date: 1 Jan 2001 From: Joan and David Dunham <dunham@erols.com>
    To: IOTAoccultations@egroups.com
    Cc: planoccult@Aula.com, occultation@skypub.com,
        seesat-l@cds.plasma.mpe-garching.mpg.de, atmob-discuss@jovian.com,
        David_Dunham@jhuapl.edu, loomberah@ozemail.com.au, mpml@bitnik.com,
        limerick@casagrande.com, wnissen@tfn.net
    Subject: AstroAlert: Stardust spacecraft may be visible Jan. 14-15
         The Stardust spacecraft is returning to the Earth for a swingby
    about two years after its launch, similar to NEAR's Earth swingby
    of 1998 Jan. 23.  The best time to watch will be when the spacecraft
    is at least 20 deg. above the horizon closest to the time of its
    closest approach at about 11:15 U.T. January 15 U.T., and before
    that closest approach, since it will be approaching the Earth with 
    a small phase angle (like NEAR) but departing with a much less
    favorable approx. 90 deg. phase angle.  For the Americas, the best
    time will be around midnight Sunday night, Jan. 14-15.  The best
    areas for observation will probably be the Orient, and Australasia,
    the western Pacific region.  You can calculate an ephemeris for
    your location using JPL's ephemeris generator at
    
    http://ssd.jpl.nasa.gov/horizons.html
    
    Modify the "current settings" to select Stardust (in the "major body"
    box) and select your city, or one near you, from their very extensive
    city database (Greenbelt, MD, is in it).  Then set the time interval
    you want, and check the quantities you want in the ephemeris.
    
    William Blume gives some predictions of the observability below,
    but based on the NEAR flyby experience, I think it will be a little
    better, with Stardust probably being 11th mag. or brighter at the
    best times in North America.  The spacecraft attitude is being 
    controlled only in a "10 deg. deadband", so there will be no solar
    panel sunglint pointings like we did with NEAR.  But you may be
    lucky and see a brief direct reflection of sunlight from the solar
    panels, which I think could be as bright as 4th to 6th mag.
    
    David Dunham, IOTA
    -----Original Message-----
    From: William H Blume [SMTP:William.H.Blume@jpl.nasa.gov]
    Sent: Monday, January 08, 2001 7:49 PM
    To: Dunham, David
    Subject: RE: Stardust Viewing
    David,
    No, the Earth flyby is run only to engineering requirements and 
    rather low staffing, so the attitude is set up for power and telecom 
    considerations.  The reflected light off the panels looks most 
    favorable in the last few hours before closest approach--and 
    unfavorable after closest approach--but with a 10-deg deadband, any 
    magnitude predict looks very uncertain.
    The following is quoted from an E-mail by George Lewis:
         When I made the ephemeris run for Stardust I assumed that
    the Stardust Project would not be willing to have the spacecraft
    perform such a sequence, and assigned a rough estimate of visual
    magnitude of 8.5 at slant range 1,000 km, phase angle 90 degrees.
    Based on experience observing artificial Earth satellites, this
    value is characteristic of a small spacecraft with an unfavorable
    orientation. With these assumptions, the brightest magnitudes that
    were obtained were about +15 at slant ranges of around 15,000 km.
    If we assume that a favorable spacecraft orientation would result
    in a magnitude difference of +5 then these brightest values would
    become +10. The delta-m of +5 is based on my observation of NEAR.
    That is to say, NEAR got up to mag 3.0 from invisibility. (It was
    invisible due to unfavorable spacecraft orientation). In my case
    "invisible" corresponded to a magnitude fainter than about 8.0 on
    acquisition (since I didn't know precisely where in the field of
    view NEAR would appear) and somewhat fainter than that when NEAR
    disappeared. The delta-m for Stardust would probably be less than
    the value for NEAR due to the fact that Stardust is smaller.
       In summary, for the most favored western Pacific stations,
    where the slant range gets as small as 15,000 km when the spacecraft
    is sunlit in a dark sky, the magnitude of Stardust might be as bright
    as +10 if the orientation is optimal. For everyone else it will be
    fainter.
      George Lewis <gdl@zeus.jpl.nasa.gov>
    
    You could contact George for more information.
    This obviously isn't something for the general public, but it will be 
    interesting to see how many talented amateurs make an attempt.
    Bill
    >Bill,
          I notice that Stardust topocentric predictions can be computed
    >from the horizons ephemeris generator Web site, but that it does not
    >give the apparent magnitude.  During the approach to the Earth,
    >will Stardust's solar panels be aimed to reflect sunlight to specific
    >areas of the Earth, as we did for about an hour during NEAR's
    >1998 swingby?
          David
    William H. Blume Phone: (818) 354-7396
    Technical Group Supervisor Fax: 393-9815
    Mission Engineering and Planning Group E-mail: wblume@jpl.nasa.gov
    Navigation and Mission Design Section
    
    Joan and David Dunham
    7006 Megan Lane
    Greenbelt, MD 20770
    (301) 474-4722
    dunham@erols.com
    
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