Satgen94 Simple Timing of Satellite Passes 14th Jan 91 by GM4IHJ Ivan G3EMU has reminded me about the simple mental arithmetic aids, to get tomorrows satellite times, if you know todays. To quote the regulars:- Satellite Mins different next day Degrees different next day NOAA 9 -13 ( eg earlier) -4 degs W ( 4 degs east) NOAA 10 -24 -5 NOAA 11 -12 -3 Feng Yun 1 -0.5 0 Uosat 2 +35 +9 Uosat 3 -28.9 -7 Pacsat -29 -7 Dove -29 -7 Weber -29.1 -7 Lusat -29.2 -7 Fo 20 +19 +6 RS 10 +30 +9 Mir +35 +16 So if Mir is EQX Equator crossing 0114 at 136 deg W today . It will be 0149 152 degs west tomorrow. Equally if you hear Mir at 0800 today , you will probablly hear it at 0835 tommorrow and 0910 the day after. All the other satellites on the list have a relatively fixed Mins difference per day, but Mir can change depending on its altitude. If it is up at 400 kms after an engine firing the mins difference per day will be 40, whereas if it is down at its very lowest altitude of 322 kms height the Mins difference per day will be about 14 minutes. Do not try to divide the minutes different by 4 and call it degrees. This does not allow for the perturbation of the orbits right ascension which in Mir's case can be as much as 6 degrees. Another point to note is that satellites in direct orbits ( inclination 90 degs or less) you work out perturbation and add minutes /4 to get degrees west per day. By contrast retrograde orbit satellites ( inclination greater than 90 degs , which includes all of the list except Mir and RS10) , you work out mins/4 - perturbation to get degrees west per day. Another point of interest mentioned by Phil GM8SNE. If you look closely at the above list you see two things :- Firstly Feng Yun EQXs and AOS hardly change at all from day to day Secondly all the Microsats are very similar. So if you hear Dove 35 minutes after Pacsat on one day , you can expect to hear Dove 35 minutes after Pacsat for at least a week there after, before their timing drifts slowly apart. RM-1 G3RWL suggests that some reports are saying that RM1 may not use the mode B anologue transponder on a regular basis, but will stick to nearly 100% Rudak packet tests. If this turns out to be the case, my recent mail suggests it will be very unpopular. As several people have pointed out to me " We already have 6 packet satellites which very few people are using. Do we really need a 7th on all the time". 73 de John GM4IHJ @ GB7SAN