Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!henry From: henry@utzoo.UUCP (Henry Spencer) Newsgroups: net.columbia Subject: Re: Launch Windows Message-ID: <5179@utzoo.UUCP> Date: Wed, 6-Mar-85 16:12:43 EST Article-I.D.: utzoo.5179 Posted: Wed Mar 6 16:12:43 1985 Date-Received: Wed, 6-Mar-85 16:12:43 EST References: <225@tellab2.UUCP> Organization: U of Toronto Zoology Lines: 24 I'm not an expert on this, but there are at least two reasons why there are definite launch windows for Clarke ("geostationary") orbit. First, remember that a satellite in that orbit remains over essentially the same spot on the equator. This means that you are not only trying to get the satellite into that orbit, it has to be in the right *place* in that orbit. There are further complications because most of the launch sites are not on the equator, which means that plane changes as well as orbital shape changes are needed. Second, most current satellites do not deploy most of their solar panels until they are in the final orbit, because the support structures are not strong enough to survive orbital maneuvering. This means that the satellites are very short of power while in transit, and the angle of the sun with respect to the solar cells is significant. (Satellites are often not free to turn to get the best angle, due to things like spin stabilization and the directions rocket motors point.) Passing through the Earth's shadow can also be a problem for a power-starved satellite. For these (and probably other) reasons, satellite launches most definitely do have time constraints as well as position constraints. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry