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February 19, 1999

Mars Polar Lander

The Mars Polar Lander spacecraft continues to perform well in early cruise.

Mars Climate Orbiter

Mars Climate Orbiter continued in semi-quiet cruise operations during the past week.

Additional diagnostic telemetry from Inertial Measurement Unit (IMU)-A was down-linked last week in further support of the investigation into noise characteristics of the ring-laser gyro control loops. Further testing is underway by the manufacturer to characterize the circumstances in which the noise phenomena is observed and to identify its cause.

Commands were also sent to the spacecraft to obtain some specialized telemetry designed to map the unused space in the telemetry buffer. These maps are being used to formulate a "housekeeping" strategy for managing the buffer free space, limiting its fragmentation.

On Tuesday, February 16, a simple test of the UHF transceiver was performed. With the orbiter in its cruise attitude, the transceiver was powered on and commanded into its nominal receive mode, in which it begins transmitting short "ping" waveforms of 150 ms duration every 3 seconds The transceiver was powered for approximately 2 hr; the X-band link with real-time telemetry was maintained throughout this period. A 46 m radio astronomy station operated by Stanford University was configured to attempt detection of the UHF-band "pings" through several different means. Spacecraft telemetry indicated nominal operation of the transceiver during this period; however, power and temperature telemetry from components located near the UHF antenna displayed an unpredicted pattern of quasi-cyclic noise spikes due to the UHF radio operation. After the transceiver was powered off all real-time telemetry returned to nominal values. The Stanford antenna was unable to detect the "ping" wavetrain in real time (the probability of doing so was not considered to be high for the detection methods attempted and due to the line of sight blockage of the spacecraft's UHF antenna in the cruise configuration). The flight team is currently evaluating telemetry from this test to better understand the interactions observed.

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