> 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 after > third stage burnout: > > http://ssd.jpl.nasa.gov/cgi-bin/eph > > Note that it will not generate an ephemeris if you start the time span earlier > 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 ephemeris: > > 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 ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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