From: Rick Baldridge (
Date: Sat Jul 31 2004 - 15:04:12 EDT

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    > JPL Horizons already contains Messenger's orbital data, and will generate
    > ephemerides for any period beginning 2004 Aug 02 at 07:10 UTC, about 2 min
    > third stage burnout:
    > Note that it will not generate an ephemeris if you start the time span
    > than the above time.
    > The ephemeris does not estimate the spacecraft's visual magnitude;
    however, I
    > have derived the following formula, for use with data provided by the
    > mag =  32.47 + 5 * log10("delta") + 0.01 * ("S-T-O" - 90)
    According to Mr. Molczan's formula and the HORIZON output for the West Coast
    of the USA, MESSENGER will be about magnitude 13.8 on Aug 2 at 8:30UT
    (1:30am PDT) a bit over two hours after launch and near its highest above
    the local horizon at 39-degrees at azimuth 275 (almost due west) and at a
    range of 31,000km.  During the course of the morning, it fades fairly
    quickly to magnitude 16 by 11h UT.  The following night, it will be almost
    straight overhead near midnight but 10-times further away (about the Moon's
    distance) at magnitude 19.1 - a difficult target for most of us.  For those
    so inclined, I highly recommend making the attempt to find MESSENGER on the
    morning of August 2nd from the West Coast.
    Rick Baldridge
    Campbell, CA
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