Current Status of the MOLA Investigation
25 Jul 2001
(Source: Goddard Space Flight Center)
The MOLA instrument was commanded off on June 30, 2001 at about 6:00 PM EDT when Mars Global Surveyor telemetry indicated that its laser operating temperature had dropped to a preset lower limit. At the time of the anomaly MOLA had been in space for 1696 days, and had undergone 216 power-on/off cycles. The MOLA laser had fired 671 million times in space and MOLA had made about 640 million measurements of the Martian surface and atmosphere. Until the anomaly, the laser energy had been nominal and steady at about 20 mJ/pulse. The June 30 event was the first anomaly in MOLA's operation since the MGS launch in November, 1996.
Effort is underway to determine the most likely cause of the anomaly. Analyses to date indicate that the likely cause appears to be an interruption of the 10-Hz laser trigger signal from the MOLA altimeter electronics. Without the trigger signal, the laser would not fire and its temperature would have dropped, eventually to the lower limit.
The first MOLA diagnostic test of a 64-minute duration was performed just after Noon EDT Saturday, July 14, 2001 and consisted of a simple turn-on. The instrument successfully returned all housekeeping packets while in maintenance mode but did not return science packets. Analysis so far is consistent with the opinion that the most likely cause of the MOLA anomaly is associated with the altimetry oscillator or first divider chip in the electronics box.
While the instrument did not assume normal operation in the first diagnostic test, the data indicate the MOLA computer is operating and that the instrument responds to commanding, which will facilitate further testing. A number of more sophisticated tests will be performed to further troubleshoot the anomaly and to understand the constraints on further operation of the instrument. The second diagnostic test will be performed the week of July 23, 2001.
Dave Smith, MOLA PI
Maria Zuber, MOLA Deputy PI
Jim Abshire, Instrument Scientist
July 25, 2001