Satgen424 MobilePhone Satellites by GM4IHJ (BID SGEN424) 10 May 97 The big commercial move into LEO low earth orbit, has started. By 2004 , we could have over 1000 new commercial communications satellites in orbit. If all systems now planned, materialise and make it into space. Five Motorola Iridium mobile phone satellites were placed in orbit on a single launch from California on 5th May 97, after hold ups on 2nd and 3rd due to high winds, and a cancellation due to ground equipment failure on the 4th. All this after an original delay in January caused by a minor Delta rocket problem, which then became a two month hold, when all Delta launches were postponed whilst the enquiry into a Delta rocket explosion over Florida, reached its verdict, and Delta launches could resume. The Iridium satellites are in an 86.4 degree inclination, 100.1 minute period orbit. When operational, the Space to Ground telephone frequencies will be in the band 1621.35 to 1626.5 MHz. Inter satellite links are in the 23.18 to 23.38 GHz band, and Gateway and Earth station links will use 19.4 to 19.6 GHz downlinks and 29.1 to 29.3 GHz uplinks. Frequency and Time Division multiplexing will be used and data will be QPSK at 2400 bps. When the Iridium network is complete , it will comprise 66 satellites in 6 different planes, 11 satellites in each plane spaced about 33 degrees apart. Elsewhere , speculation appears to be the rule. At the low end , OrbComs store and forward system which launched 2 satellites in April 95 , has not added any more of the planned 20+ satellites, and may turn out to be a non starter unless more satellites launch soon. At the expensive end . Teledesic's proposed 324 satellite constellation ( down in numbers from 800+), is condemned by some financial consultants as a potential financial disaster. But this has not stopped progress on design and planning , although McCaw Cellular appear to have withdrawn from the project. Meanwhile Hughes, Loral and Motorola all seem to think that Teledesic may be right to suggest a worldwide , wide band Internet link using LEO sats is viable, and they too have stated that they are working on solutions. At the moment , the big questions are :- (1) Will Iridiums LEO constellation of mobile phone sats work well, or will the prize go to the other companies such as Loral Globalstar, TRW Odyssey and ICO Global Communications , all of whom propose simpler systems in higher orbits? (2) If any of these LEO or Medium Height systems succeed , will they render the less versatile geostationary mobile phone systems obsolete? (3) If Iridium proves the viability of the LEO mobile phone route, will similar LEO satellite fleets, offering wide band Internet coverage, follow a few years behind? In the answers to these questions, there lies the fate of billions of commercial dollars, and a whole series of lessons for amateur radio, where perhaps we too may find we went the wrong way , ignoring LEO orbiters, and going for very expensive, high elliptical orbiters.