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September 8, 1999

Mars Climate Orbiter (MCO)

During the past week the flight team mounted an intense effort to conduct a series of diagnostic tests of the spacecraft's ability to safely move its solar array in and out of its stowed position. This testing was motivated by behavior observed following the completion of Trajectory Correction Maneuver #3 (TCM-3) on July 25, in which the spacecraft had some difficulty in its initial attempt to unstow the array following the maneuver. The array was ultimately unstowed and repositioned to its proper cruise orientation by the spacecraft's articulation control system on that day.

Last Friday (September 3), in-flight testing revealed that small tabs on the solar array, designed to passively restrain the array while stowed, were making unexpected contact with the spacecraft bus during the stow/unstow procedure. Over the weekend the team updated the stow/unstow procedure to avoid the contacted area and retested these commands in the MCO simulator in Denver, in preparation for an additional in-flight test which was conducted today. This test, just completed, verified that the team's modified commands succeeded in accomplishing the stow/unstow movements without any spacecraft/solar array contact. The team is now proceeding with additional testing of the command sequences for Mars Orbit Insertion and aerobraking using the updated stow/unstow procedure.

In addition, the flight team is beginning development of the fourth and final course correction, TCM-4, to be executed prior to Mars arrival. TCM-4 is scheduled to take place in one week, eight days prior to orbit insertion.


Mars Polar Lander (MPL)

Mars Polar Lander continues to perform well, with no activities planned during the previous week. The flight team has finished preparations for the second and final comprehensive science instrument checkout, which will take place tomorrow (September 9). Also included is the 8th check of meteorology package sensors, which have been conducted approximately once per month throughout cruise. Following this activity, data transmission from the instruments will be completed by September 12. Subsequently, the next MPL activity scheduled to occur is Trajectory Correction Maneuver #3 (TCM-3), on October 7.

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