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From: eder@ssc-vax.UUCP (Dani Eder)
Newsgroups: net.space
Subject: Re: communications satellite insurance rates
Message-ID: <237@ssc-vax.UUCP>
Date: Wed, 25-Sep-85 13:15:19 EDT
Article-I.D.: ssc-vax.237
Posted: Wed Sep 25 13:15:19 1985
Date-Received: Fri, 27-Sep-85 04:12:20 EDT
References: <536@petrus.UUCP> <528@riccb.UUCP> <539@petrus.UUCP> <530@riccb.UUCP> <564@petrus.UUCP>
Organization: Boeing Aerospace Co., Seattle, WA
Lines: 26

In response to Phil Karns question about why the Shuttle can't deploy
comsats immediately like an expendable:

     Communications satellites live in Geosynchronous Orbit, where they
orbit the earth every 24 hours.  Since the earth also rotates every 24
hours, the satellite appears to hang over a single spot on earth.  To
get to that specific location as quickly as possible, so as to start
producing revenue for the satellite owner as soon as possible, you want
a transfer orbit that intersects your destination.  

     You start a satellite on it's way to Geosynchronous one-half orbit
earlier in low earth orbit.  The shuttle orbit , and hence the initial
satellite orbit, remains fairly stationary in inertial space, inclined
28.5 degrees to the equator.  The transfer orbit is attached to the destination
in GEO, which is moving around once per 24 hours.  Thus once every 24
hours there is an opportunity to deploy and inject a comsat.

     This is why comsats are generally launched one per day starting
with the first mission day.  If the satellites are spaced fairly far
apart in GEO, it would be possible to launch two or more in one day.
The alternative, which takes longer, is to launch the satellite as
soon as possible.  The satellite then arrives at the wrong place in
GEO>  YOU MAKE your orbit slightly un_synchronous< and drift to the
correct location>   this takes weeks>

DANI EDER ??? boeing >> ssc_VAX!eder