After experiencing difficulties in communicating with the Mars Pathfinder spacecraft for the past three days, the operations team was able to reestablish a brief two-way communications session Tuesday using the lander's auxiliary transmitter. Receipt of this beacon signal indicated that the spacecraft is still operational.

The team began having communications problems with the spacecraft on Saturday, Sept. 27. These problems could be related to degradation of the spacecraft's battery. The last successful data transmission cycle from Pathfinder was completed at 3:23 a.m. Pacific Daylight Time on Sept. 27, which was Sol 83 of the mission.

No signal was received from the spacecraft on the next Martian day, Sol 84, which began in the evening of Sept. 27. The team's transmission session began at 11:15 p.m. PDT. The lack of a signal, at that time, was thought to be caused by a possible computer reset incident, ground system problem or low voltage condition. A reset or a low voltage condition, caused by the aging of the battery, would cause the spacecraft sequence to automatically stop and not execute its planned communication with Earth.

The team attempted to communicate with the spacecraft again on Sept. 29 (Sol 85) and Sept. 30 (Sol 86) with no success.

Tonight, on Sol 88 of the mission, the team will use the auxiliary transmitter again to attempt to acquire engineering data that will help them assess the cause of the communications problem. Meanwhile, the rover, which receives its instructions from Earth via the lander, is currently running a contingency program which has instructed it to stand still rather than begin its trek around the lander.

The team will repeat these activities on subsequent days and attempt to receive telemetry that will give them more information about the health of the lander and rover.

If Pathfinder operations do not return to normal tonight, a Mars Pathfinder team representative will provide an update on the situation at the beginning of the planned Mars Global Surveyor science news briefing at 9 a.m. PDT on Thursday, Oct. 2.

The Pathfinder team used today's passes over the 70 meter Deep Ppace Network stations in Canberra and Madrid, to attempt to get engineering data from the spacecraft. Although we were not able to obtain engineering data as we had hoped, we did learn another important piece of information that has assisted us in putting more pieces of our puzzle together. By watching the signal from Pathfinder's auxiliary transmitter were able to see when the spacecraft powered on this morning. The power on was later than expected due to what appears to be extra loads on the spacecraft. We believe that these loads may be the result of some hardware failure, or may have been caused by sequences that run every morning when the spacecraft wakes up.

Normally execution of our morning sequences is not a problem. However, since we believe that the spacecraft battery may no longer be operating ,the spacecraft has lost track of time. This loss of time causes loads to be turned on when there may not be enough power to support them. The initial lack of power is due to the fact that the Sun has not risen high enough to fully illuminate the solar panels and provide the required power. The spacecraft will not power on until it determines that there is enough power to operate its critical systems.

This will cause the spacecraft to wake up later in the morning and power off sooner in the afternoon than we would normally expect. This may explain some of the behavior we have been seen in the last several days. Tomorrow we will once again attempt to receive engineering telemetry data from the spacecraft. We will also be sending commands to put the spacecraft in the safest state possible for the current no battery situation. This will include taking the battery off-line. We expect to receive signals from the auxiliary transmitter indicating the completion of certain events that have been executed to save the spacecraft.

Although the exact causes of our communication problems have not been identified, we do believe that they are related to the degradation of the spacecraft battery. We have over the past two days received good indication that the spacecraft is commandable and able to communicate with us via the auxillary transmitter.

This information means that we can continue to operate the spacecraft. The spacecraft will gradually move towards using the other antennas and transmitters and will verify they are operating correctly.

For more information, please visit our website at http://mpfwww.jpl.nasa.gov. or call our Mission Status Report line at 1-800-391-6654.