PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

Mars Pathfinder Mission Status
July 12, 1997
12:45 a.m. Pacific Daylight Time
Flight controllers reestablished radio contact with the Mars Pathfinder lander tonight and repositioned the Sojourner rover after an initial communications session did not take place because the spacecraft's computer reset itself.

Beginning at about 3 p.m. Pacific Daylight Time Friday, the flight team sent commands to the Pathfinder lander instructing the Sojourner rover to back away from a rock nicknamed Yogi. The rover had been lodged against the rock since Wednesday evening; it was believed that commands sent Thursday to move the rover were not received by the lander because of an error in the timing of a radio uplink session.

The flight team received a signal from the Pathfinder lander's low-gain antenna at 6:47 p.m. Friday confirming that the lander received Friday's commands and was beginning to execute them. The team then expected to receive data over the lander's high-gain antenna beginning at 8:47 p.m. However, no signal was received at that time.

The team then sent a command to the Pathfinder lander via its low-gain antenna at about 9:45 p.m. instructing the lander to send a signal back to Earth. This signal was received. Flight controllers concluded that the lander's computer must have reset itself sometime between 6:47 and 8:47 p.m. PDT Friday evening. The commands to move the rover would not have been executed, because they were scheduled to take place later.

Commands were then sent at about 11 p.m. instructing the lander to point its high-gain antenna at Earth and begin a half-hour downlink session sending engineering data reporting on the status of the lander and rover. Commands were also sent to back the rover away from Yogi. Another command instructed the lander to take and transmit an image of the rover confirming that the repositioning had been completed.

At 12:15 a.m. PDT, the Deep Space Network station near Canberra, Australia, acquired a signal from the Pathfinder lander at the beginning of a half-hour downlink session sent via the lander's high-gain antenna. Data sent during this session indicated that the rover did in fact receive and execute commands to back it away from the Yogi rock and reposition itself on Thursday. It reexecuted these commands when they were resent Friday. In addition, an image was received at about 12:25 a.m. which showed the rover backed away from Yogi.

Friday evening marks the second time that the Pathfinder lander's computer has reset itself since its landing July 4. The flight team is not certain why the resets are taking place, but engineers noted that both incidents occurred during periods of heavy communication between the lander and rover.

Telemetry indicated that all spacecraft and rover systems are performing normally. Today is Sol 8 of the Mars Pathfinder mission.

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