[meteorite-list] Mars Exploration Rover Mission Status - October 21, 2004

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Oct 21 17:53:28 2004
Message-ID: <200410212152.OAA10179_at_zagami.jpl.nasa.gov>

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

Guy Webster (818) 354-6278
Jet Propulsion Laboratory, Pasadena, Calif.

Don Savage (202) 358-1727
NASA Headquarters, Washington

News Release: 2004-261 October 21, 2004

Mars Exploration Rover Mission Status

A problem that affects the steering on NASA's Mars Exploration
Rover Spirit has recurred after disappearing for nearly two
weeks.

Engineers at NASA's Jet Propulsion Laboratory, Pasadena, Calif.,
are working to fully understand the intermittent problem and
then implement operational work-arounds. Meanwhile, Spirit
successfully steered and drove 3.67 meters (12 feet) on Oct. 17.

Rover engineers are also analyzing a positive development on
Spirit's twin, Opportunity: a sustained boost in power
generation by Opportunity's solar panels.

Both rovers have successfully completed their three-month
primary missions and their first mission extensions. They began
second extensions of their missions on Oct. 1.

Rover engineers refrained from driving Spirit for five days
after an Oct. 1 malfunction of a system that prevents wheels
from being jostled in unwanted directions while driving. Each of
the front and rear wheels of the rover has a motor called a
steering actuator. It sets the direction in which the wheel is
headed. The steering actuators are different from the motors
that make the wheels roll, and hold the wheel in a specific
direction while driving. A relay used in turning these steering
actuators on and off is the likely cause of the intermittent
nature of the anomaly.

The relay operates Spirit's right-front and left-rear wheels
concurrently, and did not operate as commanded on Oct. 1.
Subsequent testing showed no trace of the problem, and on Oct.
7, the rover steered successfully and drove about 2 meters (7
feet), putting it in position to examine a layered rock called
"Tetl" for several days. However, the anomaly occurred again on
Oct. 13, and the problem appeared intermittently in tests later
last week.

"We are continuing tests on Spirit and in our testbed here at
JPL," said Jim Erickson, Mars Exploration Rover project manager
at JPL. One possible work-around would be to deliberately blow a
fuse controlling the relay, disabling the brake action of the
steering actuators. The rovers could be operated without that
feature. "The only change might be driving in shorter steps when
the rover is in rugged terrain," Erickson said.

Spirit has driven a total of 3,647 meters (2.27 miles) since
landing, more than six times the distance set as a goal for the
mission. Its current target is a layered rock called "Uchben" in
the "Columbia Hills." Opportunity has driven 1,619 meters (just
over a mile). Its latest stop is a lumpy boulder dubbed "Wopmay"
inside "Endurance Crater."

The daily power supply for each rover comes from 1.3 square
meters (14 square feet) of solar panels converting sunlight into
electricity. Just after the landings in January, the output was
about 900 watt-hours per day for each rover -- enough to run a
100-watt bulb for nine hours. As anticipated, output gradually
declined due to dust buildup and the martian seasonal change
with fewer hours of sunlight and a lower angle of the Sun in the
sky. By July, Spirit's daily output had declined to about 400
watt-hours per day. It has been between 400 and 500 watt-hours
per day for most of the past two months.

Opportunity, closer to Mars' equator and with the advantage of a
sunward-facing tilt as it explored inside the southern half of a
crater, maintained an output level between 500 and 600 watt-
hours per day in June, July and August. Since early September,
the amount of electricity from Opportunity's solar panels has
increased markedly and unexpectedly, to more than 700 watt-hours
per day, a level not seen since the first 10 weeks of the
mission.

"We've been surprised but pleased to see this increase," said
Erickson, "The team is evaluating ways to determine which of a
few different theories is the best explanation."

Possible explanations under consideration include the action of
wind removing some dust from the solar panels or the action of
frost causing dust to clump. "We seem to have had several
substantial cleanings of the solar panels," Erickson said.
JPL, a division of the California Institute of Technology
in Pasadena, manages the Mars Exploration Rover project for
NASA's Science Mission Directorate, Washington. Additional
information about the project is available from JPL at
http://marsrovers.jpl.nasa.gov/ and from Cornell
University, Ithaca, N.Y., at http://athena.cornell.edu .

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Received on Thu 21 Oct 2004 05:52:21 PM PDT