[meteorite-list] Spirit Condition Upgraded as Twin Rover Nears Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:08 2004
Message-ID: <200401250107.RAA23381_at_zagami.jpl.nasa.gov>

Guy Webster (818) 354-5011
Jet Propulsion Laboratory, Pasadena, Calif.

Donald Savage (202) 358-1547
NASA Headquarters, Washington, D.C.

New Release: 2004-034 January 24, 2004

Spirit Condition Upgraded as Twin Rover Nears Mars

Hours before NASA's Opportunity rover will reach Mars, engineers
have found a way to communicate reliably with its twin, Spirit, and
to get Spirit's computer out of a cycle of rebooting many times a
day.

Spirit's responses to commands sent this morning confirm a theory
developed overnight that the problem is related to the rover's two
"flash" memories or software controlling those memories.

"The rover has been upgraded from critical to serious," said Mars
Exploration Rover Project Manager Peter Theisinger at NASA's Jet
Propulsion Laboratory, Pasadena, Calif. Significant work is still
ahead for restoring Spirit, he predicted.

Opportunity is on course for landing in the Meridiani Planum region
of Mars. The center of an ellipse covering the area where the
spacecraft has a 99 percent chance of landing is just 11 kilometers
(7 miles) from the target point. That point was selected months
ago. Mission managers chose not to use an option for making a final
adjustment to the flight path. Previously, the third and fifth out
of five scheduled maneuvers were skipped as unnecessary. " We
managed to target Opportunity to the desired atmospheric entry
point, which will bring us to the target landing site, in only three
maneuvers," said JPL's Dr. Louis D'Amario, navigation team chief for
the rovers.

Opportunity will reach Mars at 05:05 Sunday, Universal Time (12:05
a.m. Sunday EST or 9:05 p.m. Saturday PST).

>From the time Opportunity hits the top of Mars' atmosphere at about
5.4 kilometers per second (12,000 miles per hour) to the time it
hits the surface 6 minutes later, then bounces, the rover will be
going through the riskiest part of its mission. Based on analysis
of Spirit's descent and on weather reports about the atmosphere
above Meridiani Planum, mission controllers have decided to program
Opportunity to open its parachute slightly earlier than Spirit did.

Mars is more than 10 percent farther from Earth than it was when
Spirit landed. That means radio signals from Opportunity during its
descent and after rolling to a stop have a lower chance of being
detected on Earth. About four hours after the landing, news from
the spacecraft may arrive by relay from NASA's Mars Odyssey orbiter.
However, that will depend on Opportunity finishing critical
activities, such as opening the lander petals and unfolding the
rover's solar panels, before Odyssey flies overhead.

Spirit has 256 megabytes of flash memory, a type commonly used on
gear such as digital cameras for holding data even when the power is
off. Engineers confirmed this morning that Spirit's recent symptoms
are related to the flash memory when they commanded the rover to
boot up and utilize its random-access memory instead of flash
memory. The rover then obeyed commands about communicating and going
into sleep mode. Spirit communicated successfully at 120 bits per
second for nearly an hour.

"We have a vehicle that is stable in power and thermal, and we have
a working hypothesis we have confirmed," Theisinger said. By
commanding Spirit each morning into a mode that avoids using flash
memory, engineers plan to get it to communicate at a higher data
rate, to diagnose the root cause of the problem and develop ways to
restore as much functioning as possible.

The work on restoring Spirit is not expected to slow the steps in
getting Opportunity ready to roll off its lander platform if
Opportunity lands safely. For Spirit, those steps took 12 days.

The rovers' main task is to explore their landing sites for evidence
in the rocks and soil about whether the sites' past environments
were ever watery and possibly suitable for sustaining life.

JPL, a division of the California Institute of Technology in
Pasadena, manages the Mars Exploration Rover project for NASA's
Office of Space Science, Washington. Images and additional
information about the project are available from JPL at

http://marsrovers.jpl.nasa.gov

and from Cornell University, Ithaca, N.Y., at
 
http://athena.cornell.edu/ .

                                -end-
Received on Sat 24 Jan 2004 08:07:51 PM PST