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Mars Pathfinder Update - October 3, 1997

MARS PATHFINDER MISSION STATUS
3 October 1997

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 antenna. 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
spacecraft 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 spacecraft 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 spacecraft. At this point the team
assessed that the spacecraft 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
was necessary to try and send data due to tracking station
elevation requirements may have been too early for the
spacecraft to have been awake. A later attempt was made to
send and activate a sequence on the spacecraft 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 spacecraft. 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 spacecraft the number of possible scenarios
is large. However, since the spacecraft 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 spacecraft 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.
Follow-Ups: