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**August 06, 2003**
**Mars Exploration Rover Mission Status**
                                    Artists concept of Mars Exploration Rover                                                The first in-flight checkouts of the science instruments and engineering cameras on NASA's twin Spirit and Opportunity spacecraft on their way to Mars have provided an assessment of the instruments' condition after the stressful vibrations of launch.

The instrument tests run by the Mars Exploration Rover flight team at NASA's Jet Propulsion Laboratory, Pasadena, Calif., finished with performance data received Tuesday from two of the spectrometers on Opportunity. 

Each rover's suite of science instruments includes a stereo panoramic camera pair, a microscope camera and three spectrometers.  The tests also evaluated performance of each spacecraft's engineering cameras, which are a stereo navigation camera pair, stereo hazard-avoidance camera pairs on the front and back of the rover, and a downward-pointing descent camera on the lander to aid a system for reducing horizontal motion just before impact.

All 10 cameras on each spacecraft - three science cameras and seven engineering cameras on each - performed well. One of the three spectrometers on Spirit returned data that did not fit the expected pattern. The other two spectrometers on Spirit and all three on Opportunity worked properly.  Teams have been busy since the tests began nearly three weeks ago analyzing about 200 megabits of instrument data generated from each spacecraft.

"All the engineering cameras are healthy," said JPL imaging scientist Dr. Justin Maki. "We took two pictures with each engineering camera -- 14 pictures from each spacecraft. Even when the cameras are in the dark, the images give characteristic signatures that let us know whether the electronics are working correctly." 

The science cameras on each rover - the Pancam color panoramic cameras and the Microscopic Imagers - all performed flawlessly. A spectrometer on each rover for identifying minerals from a distance, called the miniature thermal emission spectrometer, or mini-TES, also worked perfectly on each rover.

Two other spectrometers - an alpha particle X-ray spectrometer and a M�ssbauer spectrometer - are mounted on an extendable arm for close-up examination of the composition of rocks and soil.  Both instruments on Opportunity, as well as Spirit's alpha particle X-ray spectrometer worked properly.  The M�ssbauer spectrometer on Spirit is the one whose test data did not fit the pattern expected from normal operation.  

"The M�ssbauer results we just received from Opportunity are helping us interpret the data that we've been analyzing from Spirit," said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the suite of science tools on each rover. "Some of the theories we had developed for what might be causing the anomalous behavior of the M�ssbauer instrument on Spirit have been eliminated by looking at the data from the one on Opportunity."

The remaining theories focus on an apparent problem in movement of a mechanism within the instrument that rapidly vibrates a gamma-ray source back and forth.

"The M�ssbauer spectrometer on Spirit is working, and even if we don't come up with a way to improve its performance, we'll be able to get scientific information out of the data it sends us from Mars," Squyres said. "But it's a very flexible instrument, with lots of parameters we can change. We have high hopes that over the coming months we'll be able to understand exactly what's happened to it and make adjustments that will improve its performance. And if the M�ssbauer spectrometer on Opportunity behaves on Mars the way it did today, we'll get beautiful data from that instrument." 

The two types of spectrometers on the rovers' extendable arms complement each other. The alpha particle X-ray spectrometers provide information about what elements are in a rock.  The M�ssbauer spectrometers give information about the arrangement of iron atoms in the crystalline mineral structure within a rock.  

As of 6 a.m. Pacific Daylight Time August 7, Spirit will have traveled 157.1 million kilometers (97.6 million miles) since its June 10 launch, and Opportunity will have traveled 82.7 million kilometers (51.4 million miles) since its July 7 launch. After arrival, the rovers will examine their landing areas for geological evidence about the history of water on Mars. 

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 http://mars.jpl.nasa.gov/mer and from Cornell University, Ithaca, N.Y., at http://athena.cornell.edu .
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Guy Webster (818) 354-6278Jet Propulsion Laboratory, Pasadena, Calif.

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

NEWS RELEASE: 2003-109
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