[meteorite-list] Spirit Resumes Driving While Analysis of Problem Behaviors Continues

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 24 Apr 2009 16:06:57 -0700 (PDT)
Message-ID: <200904242306.QAA03679_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.cfm?release=2009-074

Spirit Resumes Driving While Analysis of Problem Behaviors Continues
Jet Propulsion Laboratory
April 24, 2009

Mars Exploration Rover Mission Status Report

PASADENA, Calif. -- NASA's Mars Exploration Rover Spirit drove on
Thursday for the first time since April 8, acting on commands from
engineers who are still investigating bouts of amnesia and other unusual
behavior exhibited by Spirit in the past two weeks.

The drive took Spirit about 1.7 meters (5.6 feet) toward destinations
about 150 meters (about 500 feet) away. The rover has already operated
more than 20 times longer than its original prime mission on Mars.

This week, rover engineers at NASA's Jet Propulsion Laboratory,
Pasadena, Calif., judged that it would be safe to send Spirit commands
for Thursday's drive. They also anticipated that, if the rover did have
another amnesia event, the day's outcome could be helpful in diagnosing
those events.

Three times in the past two weeks, Spirit has failed to record data from
a day's activity period into non-volatile flash memory. That is a type
of computer memory where information is preserved even when power is
off, such as when the rover naps to conserve power.

"We expect we will see more of the amnesia events, and we want to learn
more about them when we do," said JPL's Sharon Laubach, chief of the
rover sequencing team, which develops and checks each day's set of
commands.

The team is also investigating two other types of problems Spirit has
experienced recently: failing to wake up for three consecutive
communication sessions about two weeks ago and rebooting its computer on
April 11, 12 and 18. Engineers have not found any causal links among
these three types of events. After checking last week whether moving the
rover's high-gain antenna could trigger problems, routine communication
via that dish antenna resumed Monday.

Spirit has maintained stable power and thermal conditions throughout the
problem events this month, although power output by its solar panels has
been significantly reduced since mid-2007 by dust covering the panels.

"We decided not to wait until finishing the investigations before trying
to drive again," Laubach said. "Given Spirit's limited power and the
desire to make progress toward destinations to the south, there would be
risks associated with not driving."

The team has made a change in Spirit's daily routine in order to aid the
diagnostic work if the rover experiences another failure to record data
into flash memory.

To conserve energy, Spirit's daily schedule since 2004 has typically
included a nap between the rover's main activities for the day and the
day's main downlink transmission of data to Earth. Data stored only in
the rover's random-access memory (RAM), instead of in flash memory, is
lost during the nap, so when Spirit has a flash amnesia event on that
schedule, the team gets no data from the activity period. The new
schedule puts the nap before the activity period. This way, even if
there is a flash amnesia event, data from the activity period would
likely be available from RAM during the downlink.

Spirit and its twin, Opportunity, completed their original three-month
prime missions on Mars in April 2004 and have continued their scientific
investigations on opposite sides of the planet through multiple mission
extensions. Engineers have found ways to cope with various symptoms of
aging on both rovers.

This week, Opportunity completed drives of 96 meters (315 feet) Tuesday,
137 meters (449 feet) Wednesday and 95 meters (312 feet) Thursday in its
long-term trek toward a crater more than 20 times larger than the
biggest it has visited so far.

JPL, a division of the California Institute of Technology in Pasadena,
manages the Mars Exploration Rover project for NASA's Science Mission
Directorate, Washington.

Media contact: Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster at jpl.nasa.gov

2009-074
Received on Fri 24 Apr 2009 07:06:57 PM PDT