In a message which bounced because it was html, Brad Young asked: > Cosmos 660 (ID=7337, 1974-044-A) has eluded me several times now > while it was predicted to be mag 4 or 5. Has anyone else had > problems sighting this sat? > > COSPAR 8336 > +36.1, -95.9 Most likely, it was fainter than predicted. As far as I know, the standard magnitude in general use for this object, 6.8 at 1000 km, 90 deg phase angle, was derived from its dimensions. Cosmos 660 was the first of 24 Vector radar calibration satellites launched between 1974 and 1994. They are reportedly 2 m diameter spheres: http://www.astronautix.com/craft/taifun1.htm Analyzing 54 of Russell Eberst's observations of 6 satellites in the series, reveals a std magnitude of 7.4 +/- 1.5; coefficient of phase = 0.115 mag/rad, which is near zero, as expected of a sphere: http://satobs.org/seesat_ref/Vector/Vector.jpg Running predictions for Brad's location in recent days, I found a 62 pass near perigee on the evening of Aug 16 local time, for which the above std mag and coefficient of phase predict maximum brightness of 5.7 +/- 1.5. So, it could easily have been 2 or 3 magnitudes fainter than expected. Note that Heaven's Above predicted magnitude 4.8, based on the commonly used std magnitude. Here is a list of Vector satellites (most of which have decayed), extracted from Jonathan McDowell's satellite catalogue: 07337 1974-044A Cosmos 660 07469 1974-076A Cosmos 687 08043 1975-069A Cosmos 752 08744 1976-022A Cosmos 807 08865 1976-049A Cosmos 822 09801 1977-006A Cosmos 891 10149 1977-067A Cosmos 930 10157 1977-070A Cosmos 933 10862 1978-046A Cosmos 1006 11262 1979-010A Cosmos 1075 11741 1980-023A Cosmos 1169 12138 1981-003A Cosmos 1238 12388 1981-033A Cosmos 1263 12852 1981-095A Cosmos 1310 13972 1983-027A Cosmos 1450 14483 1983-111A Cosmos 1508 14668 1984-007A Cosmos 1534 15584 1985-018A Cosmos 1631 17050 1986-083A Cosmos 1788 18668 1987-103A Cosmos 1902 19320 1988-060A Cosmos 1958 20064 1989-045A Cosmos 2027 20774 1990-078A Cosmos 2098 23278 1994-061A Cosmos 2292 Ted Molczan ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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