Ahh, how quickly we blame software. The actual problem appears to
be hardware (see article below) that is causing the computer to
reboot about once every minute. Last I heard from NASA, Spirit
did an unexpected 73 Mbit dump of electrical subsystem information,
which would seem to support NASA's theory of hardware failure, via
the 128 Kbit/sec uplink to the Orbiter. And, BTW, it is NASA's
software running on VxWorks that is allowing the reboot to occur
due to a watchdog timer expiration, i.e., NASA's software is not
resetting the timer before it expires. The OS has nothing to do
with it, in this case. ;-)
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NASA fights to revive Spirit on Mars
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By Richard Stenger
CNN
(CNN) --Attempting to diagnose a nearly mute and temporarily delirious
spacecraft more than 100 million miles away, NASA mission controllers
said Friday that they suspect a hardware problem on the six-wheeled Mars
rover may have caused a severe malfunction.
The craft, Spirit, has sent back little more than beeps and sporadic
data bursts since Wednesday, forcing NASA engineers to scramble for
answers at an inopportune time: an identical robot ship is poised to
land on the other side of Mars on Saturday night or Sunday morning.
Cautioning that they will need more time to understand what went wrong,
project engineers said they have determined that Spirit has rebooted or
tried to reboot itself more than 60 times a day since the failure.
The preliminary health checkup includes both bad news and good news for
the $400 million mission, designed to search for evidence of water on
the red planet in the ancient past. First the bad.
"We will not be restoring functionality to Spirit for some time, for
days or weeks, even in the best of circumstances," Pete Thiesinger, Mars
rover project manager, told reporters at NASA's Jet Propulsion
Laboratory in Pasadena, California.
A measure of hope
-----------------
Now the good. NASA engineers think they can maintain the spacecraft's
current health for some time, communicating simple commands and
receiving simple replies, but nothing comparable to the flood of
geological and photographic data from the first 18 days of the mission
in Gusev Crater, a roughly 100-mile-wide pockmark thought to have once
been filled with water.
"I expect we will get functionality back from this rover," Thiesinger
added. The chances that it will be perfect again are not good. But the
chances that will not regain functionality are low, too, he said.
The culprit remains a mystery, but engineers have pinpointed the time
when the glitch began. Spirit was using an onboard motor to move its
thermal spectrometer for a test when the motor unexpectedly conked out.
After that, its messages to Earth became sporadic, feeble and in some
cases garbled. More detective work determined that its processor
repeatedly wakes up, attempts to load software data, finds a problem and
then presses its own reset button.
JPL engineers have coaxed Spirit back into regular and coherent contact
with Earth, albeit in very simple conversations. They think one possible
cause is that a hardware system has broken and affected the software
somehow.
"We're a long, long way from being done here, but we have serious
problems and our ability to work around them is unknown," Thiesinger said.
Into thin Martian air
---------------------
If performing long-distance therapy on Spirit were not enough, NASA must
guide an identical twin rover to a landing in Meridiani Planum, a
high-elevation plain loaded with a mineral that often forms in the
presence of water.
The Martian atmosphere is much thinner there than it is where Spirit
landed, and a recent dust storm in the region thinned it even further.
The conditions mean that Opportunity's parachute will have a harder time
slowing the craft as it prepares to land.
To compensate, the craft will deploy its parachute much sooner before
touchdown, which is scheduled for 12:05 a.m. ET.
"This will be challenging because it's the highest-altitude landing that
NASA has ever attempted," said Wayne Lee, the engineer in charge of
Opportunity's entry, descent and landing.
Find this article at:
http://www.cnn.com/2004/TECH/space/01/23/spirit.contact/index.html
