March 1997 Volume 6 Number 1

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MGS and TES Status: February 10, 1997




by Greg Mehall, TES Systems Engineer, Arizona State University


After the loss of Mars Observer, in August 1993, many thought that our chances of exploring Mars were lost as well. However, after three and a half years of hard work and dedication, Mars Global Surveyor (MGS) has put us back on track for the Red Planet!

The most exciting event so far for the MGS Thermal Emission Spectrometer (TES) team was the turn-on of our instrument on November 23, 1996. Just a few weeks after launch, we got to operate the TES to make sure it was functioning properly after being subjected to the violent vibrations of launch. We were all excited to see the first data show up on our computers at Arizona State University (ASU). The TES was operating perfectly!

The next day the spacecraft was maneuvered so that TES could view the Earth. In this test, we used the Earth as a point source of thermal energy to map out TES's fields of view. Since the MGS was about 3 million miles from Earth during this test, our planet filled only 10% of each detector. The data from this test verified that the TES had survived launch and that the optics were still aligned. Even at this great distance, TES was able to detect some of the key gases in Earth's atmosphere! The TES spectra showed Carbon Dioxide, Water Vapor, and Ozone. Together, these three gases might be interpreted to mean that Earth is a habitable planet. The spectrum of Earth can be seen by clicking HERE.

The TES was operated for four days in November, and all of the data showed that the TES instrument is working very well. If you would like to see the data from these tests, you can visit our WWW site

(/TESCruise/TESFirst.html).

During the first two weeks after the November 7th launch, the spacecraft team at Lockheed Martin Astronautics (LMA) in Denver, Colorado, tested all of the spacecraft subsystems. Except for the solar panel problem that I described in the last TES News, all of the spacecraft subsystems are working as expected. Shortly after launch, it was discovered that one of the solar panel arrays did not open completely. Analysis of the spacecraft telemetry indicated that the inner hinges that connect this solar panel to the spacecraft had jammed at about 20° short of the full, locked position. Since this discovery, the spacecraft team devised several tests to verify and characterize the problem. During much of the month of December, the flight team conducted "wiggle" tests to collect diagnostic data on the panels.

CLICK FOR FIGURE: Mars Global Surveyor solar panel hinge situation. Compare left solar panel with right solar panel.

The first round of tests did not resolve the problem but they did help to understand the cause. Engineers believe that the obstruction is a broken shaft from the solar array's deployment / damping mechanism. The shaft probably broke sometime during the launch or during solar array deployment, and then wedged itself in a position to keep the panel from opening to its proper position. Using the information learned from these tests, the flight team is currently devising a new group of tests to try to clear the obstruction. Both solar panels are generating power and pose no risk to cruise operations, but the undeployed panel could complicate the aerobraking activities that occur after MGS goes into orbit around Mars.

CLICK FOR FIGURE: Mars Global Surveyor in Mapping Configuration, showing all of the relevant parts labelled.

 The next TES power-on test is scheduled for the week of August 4, 1997. We will test several flight software modifications at that time. We also hope to be powered on, along with the MGS camera, during the last month of cruise, prior to reaching Mars. Over the next six months we will also be focusing our efforts on preparing for aerobraking and mapping activities that will occur after the successful Mars Orbit Insertion (MOI) on September 12, 1997. I will update you on the remaining spacecraft and instrument cruise activities on our way to Mars in the next edition of TES News. Until then... To Mars!

TES News is published quarterly by the Arizona Mars K-12 Education Program. This newsletter may be copied for EDUCATIONAL PURPOSES ONLY.

EDITED BY Kenneth S. Edgett, Arizona Mars K-12 Education Program, Arizona State University, Tempe, Arizona, USA.
E-mail: ken.edgett@asu.edu