(I think that) Ed Cannon wrote... >Molniya 1-64 20184 x 92 km >1 15977U 85074A 00040.65654808 .01782425 -50777-5 27938-3 0 612 >2 15977 61.8758 170.3507 6082369 259.5424 31.7975 4.09062855 51348 > >I'd kind of like to see a fair-sized object whose apogee is >20000km pass through the zenith at a height of 92 km! However, >I suppose that it might not be very shiny by the time its >perigee is that low.... A word of warning about the "apogee x perigee" heights appearing in the "line zero" of some elsets (such as those in the elset files I maintain). These heights are computed via from the mean motion and eccentricity in a convenient but simplistic way that takes no account of the Earth's oblateness. In fact, they are the heights of the satellite at its apogee and perigee measured above a sphere of the Earth's equatorial radius. Since this Molniya (like most other Molniyas) has its perigee near southern apex (its most southerly point), the actual height above ground at the perigee is more like 108 km than the 92 km given, and it is the 108 km that needs to be used when considering the atmospheric drag it will be experiencing. There should also be a second health warning relating to the accuracy of the implied perigee heights for such eccentric objects. It is not unusual to see wild swings of 10-20 km in the perigee, simply because of errors in fitting an orbit to observations made. presumably, closer to apogee than perigee. For example, only a few hours after posting the above elset, SpaceCom issued the following one suggesting (in error) an even deeper perigee... Molniya 1-64 20073 x 67 km 1 15977U 85074A 00041.38692267 .01871734 00000-0 64408-4 0 629 2 15977 61.8761 170.0957 6081430 259.5125 30.8419 4.11601382 51377 The elsets issued since then show perigee "heights" in the range from 94 to 98 km. Alan -- Alan Pickup | COSPAR 2707: 55d53m48.7s N 3d11m51.2s W 156m asl Edinburgh | Tel: +44 (0)131 477 9144 Fax: +44 (0)870 0520750 Scotland | SatEvo page: http://www.wingar.demon.co.uk/satevo/ ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www2.satellite.eu.org/seesat/seesatindex.html
This archive was generated by hypermail 2b29 : Fri Feb 11 2000 - 15:07:41 PST