From: John Conover <john@email.johncon.com>
Subject: forwarded message from John Conover
Date: Mon, 3 Mar 1997 11:47:42 -0800
Will be a sad day ...
John
There is a BTW at the end of this, which I think all have seen.
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Message-ID: <"F6NWV2.0.li.Ijn6p"@netcom13>
From: John Conover <conover@netcom.netcom.com>
To: John Conover <john@email.johncon.com>
Subject: Pioneer 10 to retire after 25 years of space exploration
Date: Sun, 2 Mar 1997 13:00:58 PST
MOUNTAIN VIEW, Calif. (Reuter) - Twenty-five years after
launch, Pioneer 10, history's longest lasting and most distant
interplanetary explorer, is being retired six billion miles from
home.
Pioneer 10's science mission -- which began March 2, 1972,
- -- ends later this month with the craft twice as far from the
sun as Pluto, officials at the NASA Ames Research Center in
Mountain View said.
``This is a bittersweet moment,'' Pioneer project manager
Larry Lasher said. ``We're celebrating one thing (the 25th
anniversary of Pioneer 10's launch), but we're sad it won't be
around much longer.''
The spacecraft's power sources are quickly degrading, Lasher
said. While the craft will continue to transmit data for about
another 12 months, ``we believe the scientific return that we
are getting at this point does not justify additional
expenditures on the mission,'' he said.
Pioneer 10 is so far away that its radio signal, traveling
at the speed of light, or 186,000 miles per second, takes more
than nine hours to reach the Earth.
Built by TRW Space & Electronics Group, a unit of Cleveland-
based TRW Inc., Pioneer 10 was launched in the same year Hewlett
Packard introduced the world's first hand-held calculator.
``By present standards, the instruments (aboard Pioneer 10)
were low tech,'' said James Van Allen, professor emeritus of
physics at the University of Iowa, and one of the principal
investigators on the Pioneer 10 mission.
Its mission was intended to last just 21 months. But to the
surprise of many scientists, it survived to become one of NASA's
most prolific interplanetary explorers. ``It has been a success
beyond any of the original objectives,'' Van Allen said.
Pioneer 10 was the first spacecraft to travel through the
asteroid belt and explore the outer solar system, the first
spacecraft to visit Jupiter, the first to use a planet's gravity
to change its course and to reach solar-system-escape velocity,
and the first to pass beyond the known planets.
On June 13, 1983, more than 11 years after launch, Pioneer
10 became the first man-made object to leave the solar system.
``It paved the way, opened the door for all the other
missions,'' said Lasher of Ames, which pilots Pioneer 10 and
collects its data. ``It broke the four-minute mile.''
At age 25, Pioneer, traveling at 28,000 mph
, is still recording the intensity of galactic cosmic rays in
the outer heliosphere, a region still under the influence of the
sun, as it races toward the heliopause, the true outer boundary
of the solar system.
Six of its original 11 instruments are functional, but the
energy produced by its generators can only operate two of them.
In the coming months the craft's power sources will continue to
degrade.
Van Allen said he would try to pressure NASA to continue
collecting at least some data from Pioneer through the end of
1997.
``It's been a beautiful mission, terribly successful,'' Van
Allen said. ``We want to keep it running as long as we can.''
But NASA maintains that the scientific value of Pioneer 10
data no longer justifies the expense, and on March 31, the
funding needed to continue mission operations at Ames will cease.
Once Pioneer 10's radio signal dies out, the ghost ship will
coast silently through deep space on its own momentum.
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--
John Conover, john@email.johncon.com, http://www.johncon.com/
BTW ...
BTW, as an interesting bit of trivia, the Pioneer has an interesting
history behind it. (Actually, in case you are curious, Neptune is now
the outer most planet-Neptune and Pluto do not have concentric orbits,
and they overlap, and Neptune will be the outer most planet well into
the next century. Thanks for sharing that, huh?)
There were two Pioneers launched, several weeks apart. The primary was
launched first, and the backup, Pioneer II, was launched later. They
were both intended to provide information on the planets, Jupiter and
Saturn. The primary was a disaster-about a week after the launch, all
sorts of stuff started to fail. Mission control at JPL initiated an
all out effort to fix things. And here is where it gets interesting.
I don't know if you have ever though about it, but one of the issues
in robotic space craft design is to determine when the robot is to
switch over to backup systems. As a case in point, how does the robot
"know" to switch over to the backup communications receiver? I mean,
if the receiver is "dead," it obviously can't receive a signal to
switch over to the backup system, right? The way this was handled was
that mission control was to send a signal every few days to the craft,
and if the craft received the signal, it would "know" that the
receiver was functional.
Unfortunately, mission control was busy piddling with the first
Pioneer, and some how or the other, the signal was not sent, and
Pioneer II dutifully switched over to its backup communications
equipment, which had far less capability than the primary.
Pioneer II, now the backup craft, running on backup communications
equipment performs its basic mission, flawlessly, (the primary craft
is now flying off through the boon docks of the solar system.) Mission
control decides that the Pioneer II, (through some very clever flight
dynamics,) could possibly be re-routed to reach the outer
planets. (Uranus, Neptune and Pluto were all somewhat aligned-a
situation that happens only very few times in a millenia-and JPL
wanted to take advantage of the opportunity.) Unfortunately, the
backup communications equipment was not capable of transmitting
signals from that distance.
A bold scheme was improvised to do something that had never been done
before. The craft's computers, in a very risky operation, would be
reprogrammed to digitally compress the video signals, (it was the
first time in history that a craft had been reprogrammed after
launch,) allowing the signal bandwidth to be reduced adequately, thus
reducing the noise level, and, with some modifications to the
receiving equipment south of Albuquerque, New Mexico, the signal could
be received from the outer planets. Very clever engineering.
As you will recall, the pictures were transmitted from JPL, real time,
world wide to the television media. The craft continued on, and is the
first man made object to exit the solar system. Time magazine has
called the craft "Nasa's Energizer Bunny."
Where is all this leading? Well, two folks affiliated with Sandia
National Laboratories were the architects of the compression and
computational marvel that made it all possible. Their names are Reed
and Solomon.
The same computer algorithm, that was hastily thrown together for
Pioneer II, is now used in all CD players, and hard disks-that's the
way store their data.
And Pioneer II? As of now, it is still working well-the plutonium
reactor that supplies electricity to the craft has run down over the
last decade to about 50% of capacity, but all systems are functional.
Plans are to permanently disable the craft in March of this year, do
to Nasa's budgetary constraints, but the craft will continue on to
somewhere in Alpha Centari, (I think it is,) where its journey will
terminate, in several tens of thousands of years ...
John
BTW, you might be careful quoting anything here-it is from my
recollections, and recollections of talking to folks at Sandia, (I was
at the University of New Mexico, studying information theory, of which
Reed and Solomon are two of the "Deans" of the science.)