Satgen 380 Oscars 10 and 13 by GM4IHJ 6th July 1996 As G3RUH pointed out Oscar 13 is likely to re enter the atmosphere in December 1996. But Oscar 10 continues to operate spasmodically, and may well provide some Phase 3 mode B operating opportunities after Ao13 has gone. Hopefully until Phase 3D gets safely into orbit. So perhaps a review of the operating conditions of Ao10 and Ao13 as of 1st July 96, is in order. Firstly Oscar 13 . The satellites perigee orbit low point is presently over high northern latitudes and may stay that way until the satellite re enters , unless drag induces a change in the argument of perigee. This means stations in the northern hemisphere can access Ao13 only briefly , and worse still this access occurs when the satellites footprint coverage is very small ( even less than Space Shuttle size). Oscar 13s perigee height is dropping about 1 Km per day. As of 1st July it was at about 224 kms which produces a footprint only 3300 kms across (ie stations 1700kms from its sub point do not see it). Meanwhile after months of declining perigee but little alteration in orbit major axis, the length of Ao13s major axis has at last started to drop ( as has the orbit period which relates to length of major axis). This indicates that the solar /lunar resonance which was pulling down perigee and increasing apogee, is no longer the critical factor. Drag is now taking control and Ao13 is heading for its funeral exactly as predicted at Amsat NA Symposium Oct 94 and reported in Amsat Journal May 95. Oscar 10 has not suffered the solar lunar resonance effects, but its poor orbit taking it into the hard radiation zone of the Van Allen Belts, resulted in a radiation dead onboard house keeping computer several years ago. Since when Oscar 10 has not accepted ground commands. None the less every few months or so its tumbling, spinning, progress temporarily aligns its solar panels somewhere near normal to the incoming sunlight. At which times the satellite is usable mode B 435 up 145 down SSB and CW. The clue to whether Ao10 is usable or not is its beacon on 145.810 Mhz. Most of the time it is sending an unstable carrier which is FMing usually about 50 Hz every 8 seconds or so ,but, sometimes as much as 150 Hz. In step with this frequency wobble, the signal to noise varies from 10 dB to 0 dB. Would be user are recommended to avoid accessing the satellite when its beacon is FMing as described above. Every so often it stops FMing and is stable , indicating relatively steady power supply via the solar panels. In some instances it has remained steady for weeks, but it is difficult if not impossible to accurately predict when these useful periods will occur. At this time (July August 96 ) Ao10 is only available to northern hemisphere stations for short periods around its orbit perigee and it is FMing. But as its perigee is higher than all the LEO satellites, it still gives better coverage than they do when its power supplies are stable. By November December 96 Ao10 will be available to northern stations almost from perigee to apogee , so maybe it will be stable then. There after when A013 goes awol, Ao10 will hopefully provide some reasonable operating periods until Phase 3D is safely in orbit.