[meteorite-list] Mars Exploration Rover Mission Status - May 26, 2004

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed May 26 20:25:07 2004
Message-ID: <200405270025.RAA05398_at_zagami.jpl.nasa.gov>

PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011

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

News Release: 2004-132 May 26, 2004

Mars Exploration Rover Mission Status

NASA's solar-powered Mars Exploration Rover Opportunity is beginning
on Thursday what controllers expect to be frequent use of an overnight
"deep sleep" mode to stretch the robot's power supply.

Opportunity has managed only one to two hours of activity on many
recent days while it has been examining a stadium-sized impact crater
from vantage points around the rim. Shutting down more completely
overnight will conserve enough battery charge to add several hours of
science operations during the day, according to Jim Erickson, Mars
Exploration Rover deputy project manager at NASA's Jet Propulsion
Laboratory, Pasadena, Calif.

There is a calculated tradeoff - an increased risk that, without an
overnight heater running, one of the six scientific instruments might
be disabled by the cold. The susceptible instrument is Opportunity's
miniature thermal emission spectrometer, called the Mini-TES. It makes
infrared observations used for identifying minerals from afar to help
the science team decide where to send the rover. Its observations also
provide close-up evaluation of rock and soil targets, and thermal
information about surface materials and the atmosphere. "The Mini-TES
gives us vital insight into the minerals in rocks and the role of
liquid water in their formation, so this choice is a carefully
considered decision to weigh the risk of losing this capability
against the benefit of continuing and increasing Opportunity's ability
to do all the other exploration-oriented things this rover can do,"
said Dr. Jim Garvin, lead scientist for Mars and lunar exploration at
NASA Headquarters, Washington, D.C.

Both Opportunity and its twin rover, Spirit, have already provided
several weeks of bonus operations after successfully completing their
primary missions: three months of examining geological evidence about
past environments at their landing sites.

As the Mars' southern-hemisphere winter advances and dust accumulates
on the solar panels, the amount of electricity the rovers can generate
is decreasing. The decline is more serious for Opportunity because the
robotic arm of that rover has a heater with a malfunctioning switch.
The switch cannot be turned off. A properly functioning thermostat
turns the heater off during the day, but the heater stays on overnight
even when it's not needed. The amount of energy wasted was not enough
to hinder Opportunity from succeeding in its primary mission, but is
now sapping about one-third of the rover's diminished amount of
solar-generated electricity.

"Deep sleep gives us a way to turn that heater off overnight," said
Opportunity Mission Manager Matt Wallace of JPL. The capability to do
so results from a software upgrade transmitted to both rovers in
April. The first use of deep sleep, on Opportunity on May 6, verified
its benefit to the useful power supply.

Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal
investigator for the rovers' science instruments, said, "Deep sleep is
going to buy us back a huge amount of capability to drive farther,
take more pictures, use the arm more." The deep sleep mode turns off a
heater for the miniature thermal emission spectrometer as well as the
troublesome heater in the arm. The spectrometer's heater uses less
power but provides important protection. Scientists and engineers
decided not to use deep sleep again after May 6 until the spectrometer
had completed high-priority observations from two different overlook
points of the crater informally named "Endurance." Those observations
were completed Tuesday.

Tests on Earth indicate the spectrometer's beam splitter, a disc of
potassium bromide salt about the size of a four-coin stack of
quarters, would become ruined somewhere in the temperature range of
minus 50 to minus 60 degrees Celsius (minus 58 to minus 76 degrees

Dr. Phil Christensen of Arizona State University, Tempe, lead
scientist for the instrument, said, "The thermal models predict that
with deep sleep, we'll go to about minus 48 Celsius. That has me
concerned because it's getting close." The May 6 deep sleep did no
damage, but next time the temperature could go lower, and it probably
will drop lower during deep sleep later in the martian winter.
Christensen concurs with the decision to take that risk in order for
the rover to have adequate power for its other activities. "We always
knew that as dust built up and we ran low on power, eventually there
would come a time when we couldn't use the Mini-TES heater," he said.
"We're getting to that point sooner because of the stuck heater on the

Meanwhile, engineers and scientists are assessing how well Opportunity
would be able to climb out of Endurance Crater. The assessment will
aid in deciding whether to send the rover into the crater for up-close
examination of rock layers there. Opportunity may complete a circuit
around the crater's rim by mid-June and be ready for a decision about
entering the crater.

Spirit, halfway around Mars, resumed normal operations May 23 after
engineers diagnosed a software glitch that halted the rover's
activities on May 21. The symptoms resembled a problem seen about a
week earlier, where again the computer encountered a conflict between
two onboard tasks. However the errors are understood and the two
incidents are unrelated. If they recur, neither pose a threat to the
rovers' health. Spirit is now less than 700 meters (0.4 miles) from
the base of the "Columbia Hills," having traveled more than 2.5
kilometers (1.5 miles) since landing. Controllers are optimistic that
Spirit will reach the base of the hills by mid-June.

JPL, a division of the California Institute of Technology, manages the
Mars Exploration Rover project for NASA's Office of Space Science,
Washington, D.C. Additional information about the project is
available from JPL at


and from Cornell University at

http://athena.cornell.edu .
Received on Wed 26 May 2004 08:24:55 PM PDT

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