Satgen345 Satellite Software Pt12 by GM4IHJ 4 Nov 95 Ancillary Programs. From time to time satellite users may need access to information which is not usually available from conventional software. Typical examples are :- Calculation of Apogee and Perigee Height. As in the case of Oscar 13 , as it comes closer each month to the earth at perigee. AO13 has been a near perfect example of several curious features of orbital behaviour, as solar and lunar gravitational resonance effects have stretched its apogee high point , higher, and pulled its perigee low point lower. Anyone with a simple Apogee perigee calculator, has only to input the latest Keplerian elements for the fate of this somewhat unlucky satellite to be followed , perhaps to its death. Calculation of Acquisition, Loss of satellite and Equator crossing times , again available via simple basic software , can give a wealth of information, when applied say to RS12, with its sub horizon propagation capabilities. A situation which can be further understood if you have software which shows the position of the solar terminator or better still maps out the theoretical ionospheric propagation profile to and from the satellite. Calculation of the location of the edge of the satellite footprint delineating the area that the satellite can see at any time. This was invaluable in the days when Russian communications ships were appearing all over the oceans , helping to fill the gaps in space station Salyut or Mir VHF communications. A minute by minute update of the Mir footprint soon revealed the location of stations the cosmonauts were talking to. More recently this software has established just which Shuttle missions would come in range of Northern Laitude stations. Eg STS 73 at 39 degree inclination has a footprint of only 16 degrees radius. So it could see to 39 + 16 = 55 north, no good for IHJ at 56.2 degrees north. Propagation Calculations. How far can you track a 1 watt 70 cm beacon from an omni directional antenna fitted onto a Mars probe. All the way to Mars ? ? No such luck , the program shows you would be lucky to hear it even to 3,000,000 miles (roughly 1/40 of the likely separation earth/mars) even if you had a super cooled front end. One day we may follow planetary probes, but they will need to operate at higher frequencies where there is some chance of high terrestrial antenna gain. No doubt readers will be able to think of other useful ancillary programs. But the one which IHJ is going to do next is a satellite fact file , listing all the operating characteristics , operating procedures and typical station hardware and software requirements. Meanwhile this ends this series of satgen bulletins discussing satellite software. PS ... Do not forget the Leonids meteor shower , 17 to 19 November probably peaking am UTC on 18th. We are not quite at the right time for one of the regular 33 year Leonids super showers ( due 1998 or 1999 ) but you never know , things might start livening up a little this year.