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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



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Posted:	Thu 7-Mar-1985 13:46 Eastern Standard Time
To:	rhea::decwrl::"net.columbia"