Mars Global Surveyor Mission Status
NASA/JPL MISSION UPDATE April 16, 1999
NASA's Mars Global Surveyor spacecraft executed an automatic response to place itself in a "contingency" mode last night after a hinge that allows the spacecraft's high-gain telecommunications antenna to point toward Earth stopped moving as planned.
When the spacecraft is in a contingency mode, it shuts down all the science instruments and initiates communications with flight controllers through its smaller low-gain antenna. Contingency mode is an intermediate step that is not as severe as when a spacecraft goes into a so-called "safe" mode.
Flight controllers at JPL in Pasadena, CA, and Lockheed Martin in Denver, CO are in the process of diagnosing the problem to determine when the antenna stopped moving. This diagnostic process will continue throughout the weekend.
There are two hinges at the end of the boom that connect to the high-gain antenna. One hinge, called the azimuth hinge, moves the antenna from side to side; the other hinge, called the elevation hinge, moves the antenna up and down. The azimuth hinge appears to have stopped moving midway between its "parked" position and its "earth-tracking" position.
The on-board sequence commands the hinge to the "earth- tracking" position before the daily communications downlink. At the end of the communication session the sequence commands the hinge to the "parked" position to minimize the gravity force on the antenna.
The hinge has functioned as planned since the antenna deployment on March 28, indicating to project engineers that the problem is not related to that event.
Mars Global Surveyor began its full-scale, two-year mapping mission of the red planet on March 9.
In its deployed and steerable position, the high-gain antenna allows the spacecraft to simultaneously make measurements of Mars and communicate with Earth without turning the spacecraft. Information from the science instruments are recorded 24 hours per day on solid-state recorders onboard the spacecraft. Then the data are transmitted to Earth once a day, during a 10-hour tracking pass over a Deep Space Network antenna.
Mars Global Surveyor is managed by JPL for NASA's Office of Space Science, Washington, DC. JPL's industrial partner is Lockheed Martin Astronautics, Denver, CO, which developed and operates the spacecraft. JPL is a division of the California Institute of Technology.
Copyright 1999 Pole Star Publications Ltd
