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From: weemba@garnet.berkeley.edu (Obnoxious Math Grad Student)
Newsgroups: sci.space,sci.space.shuttle
Subject: Voyager success
Message-ID: <12026@agate.BERKELEY.EDU>
Date: 13 Jul 88 09:45:29 GMT
References: <1222@thumper.bellcore.com>
Sender: usenet@agate.BERKELEY.EDU
Reply-To: weemba@garnet.berkeley.edu (Obnoxious Math Grad Student)
Followup-To: sci.space
Organization: Brahms Gang Posting Central
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In-reply-to: karn@thumper.bellcore.com (Phil R. Karn)

In article <1222@thumper.bellcore.com>, karn@thumper (Phil R. Karn) writes:
>Good point. But how many applications really require six second response
>time? Voyager seems to have been highly successful without humans on
>board, despite round trip times measured in hours.

Yes, it has been highly successful.  But not without some extreme diffi-
culties.  [The following is based on the 10/86 S&T account.]

The first major nasty for Voyager 2 was the radio receiver short-circuited
eight months after launch.  The backup proved incapable of changing fre-
quencies.  All this time mission control has had to estimate, within 100
Hz, the effective receiving frequency (the instrument is very sensitive
to temperature).  This is not easy, and a misguess as V2 nears Neptune
could prevent any essential last-minute corrections from taking place.

The second major nasty for V2 was the gearing that controlled the optical
istruments went berserk and then jammed to a halt shortly after reaching
the far side of Saturn.  Numerous photo-opportunies were lost.  The prob-
lem took several years for JPL to diagnose.  It was rather fortunate that
simply heating and cooling got the gears unjammed.  For once, the long time
scales proved a boon.

The third major nasty for V2 was related to the reprogramming of the error
correcting code from a wasteful Golay code to a bit-spartan Reed-Solomon
code.  Six days before U-day the JPL monitor pictures began to go blooey.
Two days were wasted trying to find the problem in JPL software, before
it was generally realized that it was V2.  A bit-by-bit check showed that
a single 0 had flipped to 1, and it couldn't flip back.  A JPL hacker
figured out--overnight--how to program around this.

There were other problems, and only a combination of good luck and ex-
cellent talent has made V2 a success.  I've got my fingers crossed for
Neptune.

ucbvax!garnet!weemba	Matthew P Wiener/Brahms Gang/Berkeley CA 94720