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From: doug@escher.UUCP (Douglas J Freyburger)
Newsgroups: net.space
Subject: Re: Voyager, on to Uranus.
Message-ID: <38@escher.UUCP>
Date: Wed, 17-Jul-85 22:32:56 EDT
Article-I.D.: escher.38
Posted: Wed Jul 17 22:32:56 1985
Date-Received: Fri, 19-Jul-85 02:04:28 EDT
References: <1792@aecom.UUCP>
Distribution: na
Organization: NASA/JPL, Pasadena, CA
Lines: 33


	A while ago, there were some questions about
Voyager 2s condition and what its chances are of hitting or
being thrown seriously off course by gravity from Uranus's
moons.  I talked it over with one of my friends in
celestial navigation and got this:

	Noone is quite sure of the mechanical condition of
the machine, but they believe it is quite fine.  There is
more worry about radiation damage to the electronics.  It
turns out that most of the electronics slowly recovers from
radiation damage if it is powered down, but there is the
tradeoff that something powered down might never come back.
Also most of the more critical circuitry in attitude
control, etc can't realistically be turned off.  It's to
risky, so they eat the accumulated radiation dameage.

	For the orbital path, the moons of Uranus are quite
small, so there is very little chance of an impact.  Even
an encounter close enough to seriously effect the
trajectory is very unlikely.  For moons of a body not yet
visited, the uncertainty in the orbit is VERY great.
Several orders of magnitude greater than the size of the
bodies, so even if you WANTed to impact one, you'd be hard
pressed.  On its pass through Saturn's system one of the
V's ended up on an impact course with Titan because of
these uncertainties.  They had several days to make the
burn, but there were still plenty of nervous space
scientist types around here at the time.

	There also seems to be plenty of delta-V left worth
of fuel, so any maneuvers to get closer to the moons will
be "no problem".