In response to one of my occasional Mir/Shuttle/(ISS) alerts for Cleveland and DC, one of my correspondents, who has not been asked for permission to disclose his identity, writes: > Thanks for the note. Why does www2.gsoc.dlr.de only list the 9:42 pm ED= > T pass > while www.hq.nasa.gov/osf/mir/a.html only lists the 8:20 pm EDT pass fo= > r > tonight. > I would think that both passes should be visible naked eye and both sit= > es > should list > both passes. Just curious. thanks. > = I respond here because my answer may be of interest to some part of the SeeSat-L readership. For some reason, your mailer didn't generate plain ASCII text. I don't think I've ever used either site which you mention, so I can only comment generally. The problem of screening passes for visibility is a central problem. Generating a correct rating is very, very difficult. Even with such a rating, a cutoff must be imposed. Implemented programs are far from ideal, often very far from ideal. Most do not actually rate, but merely impose various criteria. Unless these criteria are very elaborate, they will be quite imperfect. Superficially, each pass must have violated some criterion. My ancient and reliable version of QuickSat generates: 41.374 81.864 840. Nissen, OH 1950 17.5 2 F F F F F *** 1998 Sept 29 *** Times are UT *** 0 2 1031 16609 Mir Complex .1 -3 H M S TIM AL AZI C U MAG REVS HGT SHD RNG EW PHS R A DEC 0 26 8 .1 42 331 C 62 -.1 40.8 371 224 541 2.2 106 1410 68.7 2 0 1 .1 8 307 71 4.9 41.8 370 28 1507 .7 140 1341 32.6 At an unfavorable phase angle, the second pass of Mir was most likely even more difficult than suggested by the predicted altitude and magnitude. Because the GSOC site generated an incorrect time, it must have been given incorrect data, probably observer location data; or have had a bad or old elset for Mir; or (not strongly indicated by this example) use very rough criteria. Cheers. Walter Nissen firstname.lastname@example.org -81.8637, 41.3735, 256m elevation --- On 1901 September 14, President William McKinley died of a gunshot wound. 45 days later, 1901 October 29, assassin Leon Czolgosz was executed for the crime, as the American people put the matter behind them and got on with the business of the country. Of course, there were fewer lawyers then, and less concern then for the rights and privileges of a little guy than for the rights and privileges of a president now.