Re: Q: GPS visibility

From: Mike McCants (
Date: Wed May 31 2000 - 12:34:17 PDT

  • Next message: Gene Heyler: "More GRO information"

    "Balcewicz, Joseph F" wrote:
    > Has anyone reported seeing a GPS (Navstar) satellite with the unaided eye?
    Not that I know of.
    > What magnitude might they be?
    Wayne Hughes wrote:
    >I figure magnitude 10-12.
    The ISI Consulting technical archive for a 1999 launch
    says that the GPS payload measures 94 inches long and 91 inches in
    diameter.  (2.4 meters long and 2.3 meters in diameter)
    This should give an RCS of about 5 or 6.
    I have intrinsic magnitudes (full phase at 1000Km) of 4.5 or 5.0 for
    the few that I have seen.  This translates into an observed magnitude
    of about 11.0 to 11.5.  Typically I used a 10 inch reflector at about
    100 power (about 8 years ago).
    However, ISI Consulting also says "with solar panels 180 degrees apart".
    I have observed flashes from some GPS payloads (perhaps as bright as
    magitude 9).
    >Satellite situation report says they have radar cross sections of 10-100,
    But my "median" values range from 2 to 50 and the median of the medians
    is about 5 or 6.  So I suspect that RCS values for these objects (and many
    other high objects) are sometimes much too high.
    >rule of thumb of a magnitude of 7.3 for a satellite with an rcs of 1 at
    My thumb says 6.3, but I always see objects brighter than they
    really are.  :-)
    >but it did get the CSL-04 99057AU fragment
    >at 1100 km and rcs=0.18 last night.
    Wow, I'm jealous.  :-)
    >I noticed in the SSR that geosynch
    >Galaxy 5 has a rcs of 760 (suggesting magnitude 7-8) and Glonass 36,
    >the Russian GPS counterpart, has a rcs of 555.  Could these be right?
    No way.  :-)
    Mike McCants
    Unsubscribe from SeeSat-L by sending a message with 'unsubscribe'
    in the SUBJECT to

    This archive was generated by hypermail 2b29 : Wed May 31 2000 - 12:38:11 PDT