Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site decwrl.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!decvax!decwrl!dec-rhea!dec-dvinci!fisher From: fisher@dvinci.DEC Newsgroups: net.columbia Subject: Launch Windows Message-ID: <1005@decwrl.UUCP> Date: Thu, 7-Mar-85 13:52:42 EST Article-I.D.: decwrl.1005 Posted: Thu Mar 7 13:52:42 1985 Date-Received: Sat, 9-Mar-85 11:33:46 EST Sender: daemon@decwrl.UUCP Organization: DEC Engineering Network Lines: 46 From: DVINCI::FISHER 7-MAR-1985 13:42 To: FISHER Subj: net.columbia > ...why are there launch windows for geosync satellites? >> ...they have to be at the right place at the right time to end up >> in the right place over the earth Well, actually there is more to it. If you end up in the wrong place in geosync orbit, it is pretty cheap to move a satellite, as long as you are not in a real big hurry. You just give it a push and let it drift. In general the OPENING of the launch window is usually defined by when the AOA (Abort Once Around) landing site (usually Edwards AFB) will have enough light. Thus try not to launch earlier than one orbit-time before sunrise at EAFB. Another important consideration is that satellites are typically designed for the conditions they will encounter during their operational life, and not a whole lot more. Ex: In operation, many geosync sats spin, and are in sunlight MOST of the time. Thus they are not designed to tolerate darkness very often, and they are not designed to tolerate direct sunlight when they are not rotating. The launch timing is critical (I think typically the window closeing is based on) the sun angles on the satellite while it is climbing to geosync altitude. Aside: I have always been amazed at how fussy and specialized space vehicles are. And you wonder why it costs $millions to keep a space vehicle like Voyager going once it is up there? Someone has to keep monitering the critter to make sure it does not exceed some weird design limitation! Burns UUCP: ... {decvax|allegra|ucbvax}!decwrl!rhea!dvinci!fisher ARPA: fisher%dvinci.dec@decwrl.ARPA Posted: Thu 7-Mar-1985 13:46 Eastern Standard Time To: rhea::decwrl::"net.columbia"