Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!linus!decvax!harpo!eagle!karn
From: karn@eagle.UUCP (Phil Karn)
Newsgroups: net.space
Subject: Re: sattelites
Message-ID: <1047@eagle.UUCP>
Date: Thu, 21-Jul-83 06:09:42 EDT
Article-I.D.: eagle.1047
Posted: Thu Jul 21 06:09:42 1983
Date-Received: Thu, 21-Jul-83 21:35:37 EDT
References: sri-arpa.3180 pur-phy.835
Lines: 21

In the interests of reducing netnews traffic in general and flame reduction
in particular, I've worked out the percentage visibility between
a shuttle orbiter and a geostationary satellite.  Using my orbit program
and a bit of geometry, I stepped through a one day period in 10 second steps,
counting the number of steps in which the shuttle can see the geostationary
satellite. The answer is 54.87%.

Assumptions:

1. The shuttle is in a ~300 km, 28.46 deg inclination circular orbit.
(Specifically I used STS-7.)
2. Not knowing the final location of TDRS-1, I used SBS-2 which is
parked at 97 deg west.  The actual position won't matter when averaged
over a long interval, since the TDRS will rotate once per day around the
shuttle's orbit plane.
3. The earth is perfectly spherical for purposes of visibility.
4. Communications aren't cut off until the earth itself actually blocks
the direct line-of-sight path. (I.e., the atmosphere is ignored.)


Phil