[meteorite-list] Prime Mission Half Over, Spirit Looks For Bonus Time

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:31:24 2004
Message-ID: <200402191809.KAA24783_at_zagami.jpl.nasa.gov>

http://www.spaceflightnow.com/mars/mera/040218spiritsol45.html

Prime mission half over, Spirit looks for bonus time
BY JUSTIN RAY
SPACEFLIGHT NOW
February 18, 2004

The first Mars Exploration Rover, beset for a time by computer troubles but
now trekking on a geology adventure to an impact crater, has reached the
midway mark of its primary mission.

Scheduled to last 90 martian days, or sols, Spirit completed the 45th workday
on the Red Planet Wednesday morning. The six-wheeled robot is currently en
route from its landing base to Bonneville Crater where it will survey the site for
eager scientists on Earth, hoping to find clues about Mars' history.

Spirit made its hectic entry, descent and landing on Mars January 3. In the
subsequent two weeks, the rover had to unfold its wheels, stand up and then
prepare to drive off its landing platform.

Once rolling the surface, the craft headed for a pyramid-shaped rock named
Adirondack. It was there that computer memory troubles struck on January 21,
knocking out communications between the rover and ground controllers. For a
time, many worried the mission could be over. But engineers struggled to regain
command of the craft, diagnose the problem and nurse Spirit back to health.

"In a nutshell the problem is as simple as this:" Glenn Reeves, flight software
architect, explained at a news conference earlier this month, "as we
accumulated additional files in the onboard file system, the system consumed
additional memory and eventually we ran out. That was problem No. 1. And
problem No. 2 is our reaction to that was fairly severe and in the course of
reacting we corrupted that same file system.

"The answer to get (the rover) back to its state where we are healthy and
pristine was basically get all of the information out of that file system that we
could and then erase the flash memory that actually holds it and to recreate the
file system on the vehicle."

It took a couple of weeks, but Spirit made a full recovery and returned to the job
it was sent to do -- finding proof that Mars once had a watery past. If the
planet did have water, it could have sustained life.

The rover is bound for Bonneville Crater to study the rocks, soil and landscape.
Unlike the drama-packed moments during the "six minutes of terror" of landing,
the science-led exploration being performed now is distinguished by the
discovery of never-before-seen parts of our neighbor planet.

"In some ways getting down on the ground and getting the rover off (the landing
base), that's the highest pressure, highest visibility period," said Richard Cook,
rover project manager. "And there is sort of almost a let down, to a certain
extent, amongst a lot of people that once you get through (those events) you
are now done with a lot of exciting stuff. It's interesting, I think, that the team's
morale and mood has, if anything, sort of turned around after that because we
are amazed about how interesting what we are seeing is and how capable these
vehicles are as far being able to drive and to look at new and interesting things.
In the case of science, it's fascinating to everybody."

Aside from the computer troubles that temporarily sidelined Spirit, officials are
pleased at how the first half of the mission has progressed.

"I think it's have gone way better than we would have expected," Cook said.
"One of our experiences on Pathfinder was that due to varying levels of
problems during the mission we would not be able to effectively use like one out
of every three days. We would have a problem with the vehicle wouldn't get the
instructions we sent for the day or we would have a coordination problem with
the (Deep Space Network communications system).

"So during our development period (for Spirit and Opportunity) we had this
mantra that if we could get two out of every three days to be successful and
productive then we would be doing very well.

"With the exception of the period of time when (Spirit) had the anomaly, we've
been doing much better than that. We've really had, knock on wood, a very long
chain of very successful days."

With Spirit is fine shape, engineers and managers are looking at plans to extend
the mission well beyond the primary goal of 90 martian days.

"We are actually in the process of doing that, to talk with the Mars program
both here at JPL and at NASA Headquarters about what they want to do as far
as an extended mission is concerned," Cook said. "Clearly, we have these
priceless assets on the surface and so we need to make the best use of them as
we can. Over time, we try to become more efficient and reduce the size of the
teams because we can do more with less.

"My expectation is that we will continue to operate them for quite a while
longer after the prime mission."

Exactly how long Spirit, and twin rover Opportunity, will continue to function in
the harsh Mars environment isn't clear.

"We are actually in the midst of doing an exercise to come up with that. In the
case of Spirit, from a power and a thermal point-of-view, we think the vehicle
will be very productive much longer beyond the 90 sols. Exactly what that
number is we're still trying to come up with," Cook said.

"The issue that is sort of at the back of everyone's mind is we do go through
these deep thermal cycles every day. So there is a concern that after we get
past sol 200 or something that we are going to start to have the potential for
some sort of problem due to the thermal cycling of the electronics and
mechanical hardware. It is very hard to predict when that will occur, so we are
continuing to proceed along with the thought that we should be trying to get as
much out of these right now as we can."

The temperature range between the cold of night and the warmth of day swings
from -95 degrees C to +10 degrees C for external components like motors,
Cook said. Internal hardware and electronics experience less severe shifts,
going from -10 degrees C to +30 or +40 degrees C.

"It is really the stuff outside that's more of a concern."

Still, the rovers could survive for twice their primary mission length.

"Doubling is certainly not out of the question. And Opportunity is in the same
condition (as Spirit)," Cook said.

Controllers expect Spirit to reach Bonneville within two weeks. What it
discovers will determine how long it spends there. For its part, Opportunity
continues to collect science data inside the tiny bowl-like crater in which it
landed 25 sols ago.

"It still remains very exciting to the team and they are looking forward every
day to seeing what these things can do," Cook said.
Received on Thu 19 Feb 2004 01:09:44 PM PST