Mars Rover Spirit Mission Status - November 4, 2003

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

News Release: 2003-144
November 4, 2003

Mars Rover Spirit Mission Status

A series of tests of one of the science instruments on NASA's Mars
Exploration Rover Spirit has enabled engineers and scientists to
identify how to work around an apparent problem detected in August.

Tests now indicate that all of the science instruments on both Spirit
and its twin, Opportunity, are in suitable condition to provide full
capabilities for examining the sites on Mars where they will land in
January.

Spirit's Mössbauer spectrometer, a tool for identifying the types of
iron-bearing minerals in rocks and soil, returned data that did not
fit expectations during its first in-flight checkup three months ago.
A drive system that rapidly vibrates a gamma-ray source back and forth
inside the instrument appeared to show partial restriction in its
motion.

"The drive system is adjustable. We can change its velocity. We can
change its frequency," said Dr. Steve Squyres of Cornell University,
Ithaca, N.Y., principal investigator for the rovers' science
instruments. "We've found a set of parameters that will give us good
Mössbauer science if the instrument behaves on Mars the way it is
behaving now."

The corrective countermeasures include using a higher frequency of
back-and-forth motion. "With these settings, whatever happened during
launch will not decrease the quality of the data we get from the
instrument," said Dr. Göstar Klingelhöfer, of Johannes Gutenberg
University, Mainz, Germany, lead scientist for the Mössbauer
spectrometers on both rovers. "The instrument was designed with enough
margin in its performance that we can make this change with no
significant science impact."

A possible explanation for the instrument's behavior since launch is
that intense vibration of the spacecraft during launch shook something
inside the spectrometer slightly out of position, he said.

Landings on Mars are risky. Most attempts over the years have failed.
And even if the spacecraft survives the landing, there is the
potential that individual components could be damaged. "One remaining
issue with the Mössbauer Spectrometer on Spirit, as with all the
instruments, is that we can't be one hundred percent sure it'll
operate on Mars the way it's operating now," Squyres said. "We'll
breathe easier once we've done all our post-landing health checks."

Another fact that has emerged from the in-flight checkouts of the
Mössbauer spectrometers on both spacecraft is that the internal
calibration channel of the Mössbauer spectrometer on Opportunity is
not functioning properly. But because the instrument has the
redundancy of a separate, completely independent external calibration
method, this problem will not hamper use of that instrument, Squyres
said.

Spirit is on course to arrive at Mars' Gusev Crater at 04:35 Jan. 4,
2004, Universal Time, which is 8:35 p.m. Jan. 3, Pacific Standard Time
and 11:35 p.m. Jan. 3, Eastern Standard Time. (These are "Earth
received times," meaning they reflect the delay necessary for a
speed-of-light signal from Mars to reach Earth; on Mars, the landing
will have happened nearly 10 minutes earlier.) Three weeks later,
Opportunity will arrive at a level plain called Meridiani Planum on
the opposite side of Mars from Gusev. Each rover will examine its
landing area for geological evidence about the history of water there,
key information for assessing whether the site ever could have been
hospitable to life.

As of 13:00 Universal Time on Nov. 5 (5 a.m. PST; 8 a.m. EST), Spirit
will have traveled 367.4 million kilometers (228.3 million miles)
since its launch on June 10 and will still have 119.6 million
kilometers (74.3 million miles) to go before reaching Mars.
Opportunity will have traveled 296 million kilometers (184 million
miles) since its launch on July 7 and will still have 160 million
kilometers (99.2 million miles) to go to reach Mars.

The Jet Propulsion Laboratory, 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

http://mars.jpl.nasa.gov/mer

and from Cornell University, Ithaca, N.Y., at

http://athena.cornell.edu http://athena.cornell.edu/ .


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