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July 28, 1999

Mars Climate Orbiter (MCO)

The sequence of commands for executing Trajectory Correction Maneuver #3 (TCM-3) were transmitted to the MCO spacecraft this past Friday, July 23. The spacecraft successfully performed this 3.3 meter/second maneuver at 05:00 PDT on Sunday morning, July 25. Post-burn navigation estimates of the flight path have verified that the maneuver was implemented very accurately, due to some "tuning" of the spacecraft's autopilot based on experience gained from TCM-1 and TCM-2. Simulated animations of TCM-3 is available on our website:

Following the maneuver, the solar array's two-axis gimbal drive was commanded to reposition the solar array to its cruise orientation, according to standard procedure. During this event the spacecraft's fault protection system detected a possible anomaly in one of the gimbal encoders, which measures angular position (there is one encoder for each of the two gimbal axes). The fault protection system automatically activated the back-up encoder for that axis, and successfully completed repositioning the solar array. Once it was back in cruise configuration, a complete health and status check of the spacecraft was performed, indicating that it was otherwise in excellent health and performing as expected. The flight team is presently evaluated recorded spacecraft telemetry to further assess whether or not the suspect encoder actually experienced a malfunction.

Mars Polar Lander (MPL)

The MPL spacecraft continued cruise operations last week, with no planned commanding or flight events due to the flight team's focus on accomplishing TCM-3 for Mars Climate Orbiter.

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