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From: karn@ka9q.bellcore.com (Phil Karn)
Newsgroups: sci.space
Subject: Re: Comsat fuel saving maneuver invented
Message-ID: <183@ka9q.bellcore.com>
Date: Sun, 19-Oct-86 19:53:43 EDT
Article-I.D.: ka9q.183
Posted: Sun Oct 19 19:53:43 1986
Date-Received: Tue, 21-Oct-86 23:12:45 EDT
References: <8610180704.AA03474@s1-b.arpa>
Organization: Home for Burned-out Hackers
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> The NY Times reported today (10/16) that engineers at Comsat Corp.
> have developed a technique for reducing the fuel consumption
> of comsats by up to 90%.  The technique can be applied remotely to
> satellite already in orbit.

I'm puzzled by this move on the part of Comsat. It has been well known for
many, many years that North/South stationkeeping is much more expensive in
terms of fuel consumption than East/West stationkeeping, and that a
satellite that foregoes N/S thrusting will describe a "figure 8" orbit whose
inclination varies cyclically with time due to lunar and solar
perturbations.  However, they're claiming that this is a new, novel and
PATENTABLE idea. I hope there's something more to it than I've heard so far,
since AMSAT has been saying (in print) for several years now that we would
only do E/W stationkeeping on our Phase 4 amateur birds in order to minimize
hydrazine requirements.

The only problem I can see with this technique is how they are going to keep
the antenna footprint in a fixed position given a spinning spacecraft.  I
guess they could reorient the spin axis so that it's always normal to the
orbit plane. This would cause a 24-hour cycle in which the footprint would
"rotate" at the equator crossings.  With a three-axis stabilized (i.e.,
non-rotating) spacecraft, however, this could be avoided.

Phil