To: Valueman who wrote (5910 ) 4/30/1999 10:56:00 AM From: RMiethe Respond to of 10852
"Losing 'lock' with a GEO can arise for a variety of reasons. GOCC actually never really has 100% certainty as to why. Though the matter is academic now, since you ask: this GEO drifted out of its slot ('box'), but GOCC never lost contact with it. There is an omnidirectional antenna on the GEO that can receive messages from GOCC, as in this case, once the computer has placed the GEO in a 'safe mode'. [The unidirectional antennas are for specific strong signals for communications in the footprint]. You have 'drift models' that tell you where the GEO should be at any given milisecond (I do mean 'milisecond') when it drifts. But the computer has to be right as to the "CAUSE" of the drift. Normally the computer will run through its own models and mix and match, so to say, what the causes are to get a location on the drift. This GEO was pretty quickly found, and brought back to its slot, and the general belief is that there was a programming error that sent this satellite adrift. The 'spin' to which you refer is/can be a 'by-product' of the programming error. While fuel was used to bring this GEO back to its slot, I can't say how much, and would not pretend to know. Will this happen again? It happened once before, as I mentioned. 'Wounded'? Too strong a term, and one that is not apt here. This sort of problem that Sol 1 had happens in 5% of communications satellites, and the issue is usually handled without publicity. It is because this is a commercial satellite that it got the publicity. It makes for a good 'rush' among Wall Streeters, but actually overstates what turned out to be a brief anomaly."