From: utzoo!decvax!cca!cobb@NBS-VMS@sri-unix Newsgroups: net.space Title: Dial-A-Shuttle Article-I.D.: sri-unix.2065 Posted: Tue Jul 13 09:27:53 1982 Received: Fri Jul 16 02:05:04 1982 The reason you don't hear all that much on the Dial-A-Shuttle number is that Houston and the Shuttle can only talk to one another when the shuttle is over a ground station, which doesn't happen all that often. The Shuttle is in such a low orbit that the horizon is only a few hundred miles, and it's moving so fast that it covers that distance fairly quickly. Twenty minutes talking to the same ground station is a long pass. You have to know when the shuttle is over a ground station in order to get anything out of the phone number besides the recording. Unfortunately, the ground stations are pretty randomly scattered, and the shuttle doesn't cover the same ones on successive orbits because the Earth rotates under it. In order to predict ground station passes, you need either: - a fairly sophisticated orbital trajectory program, or - a copy of NASA's flight plan, which has (among other goodies) a map of the shuttle's ground track, including markers indicating which ground stations are in communication with the shuttle at what times. Once you correct for the difference between planned and actual liftoff times, the map is very accurate. The flight plan is included in the Shuttle Mission Press Kit (at least it was in the one for STS-3), so pester your friendly neighborhood newspaperman. Second topic: The article I read said that AT&T had collected $1.2 million dollars on that number during the last mission. That's not peanuts! That's quite a few percent of the cost of the mission. What are the chances of NASA collecting some royalties here? After all, they're \providing/ the signal; Ma Bell is just moving it around. Even if NASA can't get any of the money directly, that sure shows that there's a helluva lot of popular support out there for the space program. Probably more than most congressmen realize... Stewart PS - Does anyone have a program for calculating ground tracks/ground station coverage? Can anyone provide pointers to the appropriate algorithms? (Supposedly they fly an HP-41 calculator on the Shuttle that's programmed to display upcoming ground stations, so it can't be that hard.)