MARS PATHFINDER MISSION STATUS
3 October 1997, 4:00 p.m. PDT

The Mars Pathfinder spacecraft team has been experiencing communication problems with the lander spacecraft on Mars. The last successful data transmission cycle was completed Saturday morning, September 27, 1997 at 3:23 am (sol 83).

On September 27, at 11:15 pm, (sol 84) no signal was received. The spacecraft was powered on at 2:00 am local Mars time to perform early morning weather measurements and sky images. The lack of a signal, at that time was thought to be caused by a possible reset, ground system problem or low voltage condition. A reset or a low voltage condition, caused by the aging battery, would cause the spacecraft sequence to automatically stop and not execute its planned communication with earth.

On September 29 at 1:30 am (sol 85) the team attempted to command the spacecraft to send a carrier signal to earth over the low gain and high gain antennae. Neither signal was received.

In the early morning of September 30 (sol 86), the team again attempted to command the spacecraft to send a carrier signal to earth over the low gain antenna. This attempt was done at Mars local noon in order to ensure maximum power on the solar arrays in order to power the s/c transmitter . No signal was received. At this point a preliminary assessment was made of possible problems. As in the past, loss of communication can be caused by problems with the ground system, flight software and/or flight hardware.

On early Wednesday morning, October 1, (sol 87), assuming a possible hardware problem, the team commanded the spacecraft to switch to its auxiliary transmitter. At first no signal was received but at approximately 4:23 am, a signal was received that lasted for about 20 minutes. The team also attempted to power on the secondary string of the main transmitter but no signal was seen.

Thursday morning, October 2, (sol 88), the team attempted to get digital data from the auxiliary transmitter. During the beginning of track the spacecraft auxiliary transmitter signal was seen again. The signal turned off at 11:30 local solar time on Mars indicating that the s/c computer had enough power to wake-up and turn off the transmitter. Because of the late wake-up there was no time to attempt to receive digital data from the s/c. At this point the team assessed that the s/c may be seeing extra loads on the bus resulting in late wake-up times. Since this could be related to a battery failure, commands were sent to put the spacecraft in a mode where it does not use the battery and takes it off-line. It is not clear whether these commands were received.

October 3, (sol 89), the team once again attempted to get digital data on the auxiliary transmitter. No data was received. However, the time of day in which it was necessary to try and send data due to tracking station elevation requirements may have been too early for the s/c to have been awake. A later attempt was made to send and activate a sequence on the s/c which put the Pathfinder in the safest state possible for a potential non-operational battery. There was no signal indicating that these commands executed on the s/c. The problem of not seeing this signal could have been ground station related.

The rover continues to be in a contingency state. Sojourner will do nothing until Sunday, October 5 (sol 91) and then will begin to drive in an arc around the lander.

The team continues to investigate a number of possible scenarios. Since so little information is currently available from the s/c the number of possible scenarios is large. However, since the s/c battery has exceeded its expected lifetime by a factor of 3, scenarios associated with the degradation of the battery are probably most likely. Learning how the s/c operates without the battery is something the team is in the process of doing.

Although the Pathfinder mission has extended far beyond its expected lifetime, the team is currently doing everything possible to attempt to get back on schedule with Pathfinder’s extended mission.

For further information on the Mars Pathfinder Mission, please call our Mission Status Report line at 1-800-391-6654.