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July 3, 1998

John McNamee
Mars Surveyor 98 Project Manager

Orbiter integration and test activities are proceeding on schedule. Troubleshooting of the Pressure Modulator InfraRed Radiometer (PMIRR) instrument optical chopper assembly at Honeywell has uncovered a faulty bearing in the chopper. This bearing is the suspected cause of the chopper anomalies which surfaced during system testing.

The Thermal and Evolved Gas Analyzer (TEGA) flight instrument and the repaired flight meteorology mast were delivered to Lockheed Martin on July 2 for installation on the lander on July 6. This completes the lander flight science payload delivery and the full flight payload will be installed on the lander for the landed thermal balance test scheduled to begin on July 18.

The medium gain antenna (MGA) on the lander was damaged during a mission profile test on June 30 due to an incorrect physical configuration of the vehicle. The MGA was moving in a normal fashion during the test when it contacted one of the lander outboard solar panels. The incorrect physical configuration involved the conduct of the test with the outboard arrays tucked up in a stowed configuration against the inboard panel rather than in the deployed configuration (which would be the normal flight configuration during any MGA motion). The inboard arrays contain notches to accommodate the full design range of MGA motion while the outboard arrays contain no notches. The technicians in the test facility noticed the problem as it was occurring but were unable to stop the MGA motion due to two other contributing factors to the incident: 1) The lander was operating on battery power which rendered the kill switch inoperative, and 2) The mission sequence was at a point of transition from X-band to UHF transmission capability which made it impossible to command the vehicle at a time when MGA motion was occurring. The damage appears to be limited to the MGA with no visible damage evident on the solar array. The MGA was shipped to Boeing on July 1 for assessment and repair.

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