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Mars Pathfinder
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Sol 79 (23 September 1997) Images




 This color image taken by the Sojourner rover's rear camera on Sol 78 (September 21) shows the Alpha Proton X-ray Spectrometer (AXPS) deployed above the rock "Chimp." Fine-scale texture on Chimp is visible. Sojourner's rear camera is used to pinpoint the position of the APXS on target rocks and soils.





 This stereo image pair taken by the Sojourner rover's front cameras was taken on Sol 76. The "Twin Peaks" (~ 1 km away) are seen on the right horizon, as is "Big Crater" (2.2 km away) at left. This new viewing perspective shows dunes and rocks not visible from the Pathfinder lander.





 This figure shows temperature measured by the Pathfinder ASI/MET instrument, 1.0 m above the level of the lander solar panels, for a period of continuous measurement during Sols 68 and 69. Measurements are obtained every 4 seconds. Temperature is given in Kelvin, and time is expressed in Sols, where 68.0 is midnight at the end of Sol 68 and 68.5 is noon on Sol 69. Coverage extends from roughly 9 am on Sol 68 to 2:30 p.m. on Sol 69. Temperatures fall from a maximum of 265 K at about 2:30 p.m. to a minimum of 196 K just before dawn at 5:30 am. During the morning and afternoon, surface heating causes turbulent convection, and temperatures fluctuate rapidly by as much as 15-20 K. At sunset and sunrise the atmosphere is stable, and temperatures vary by significantly less than 1 K in the short term. During the night, the atmosphere is also stable with cold air near the surface, but is disturbed frequently by downslope winds which produce short-term temperature fluctuations of a few degrees. This figure shows pressure measured by the ASI/MET instrument during the period covered by the temperature figure described above. Both diurnal (daily), semidiurnal (twice-daily), and higher order variations can be seen clearly. Peak-to-peak variations are approximately 0.3 mbar, or 5% of the mean pressure. The daily pressure minimum occurs at sunset and the maximum is usually found shortly after sunrise. Narrow pressure minima, produced by 'dust devils', can be seen at Sols 67.486, 67.560, and 68.535.


22 September 1997, 11:00 p.m. PDT

All Sol 79 uplink and downlink activities have been completed. Actually, the downlink ended about 45 minutes early today due to an unexpected drop in the downlink signal strength being detected on the ground. Troubleshooting here on Earth failed to reveal what the problem might be, but once contact is reacquired with the Pathfinder lander tomorrow evening, we hope to better determine what the problem might have been.

The Earth rose above the Martian landing site at 2 PM PDT, and the Sun shown on our Martian dwellers at 4:30 PM PDT today. Data was returned from Mars today using the Deep Space Network stations in Canberra, Australia. Up until the final drop in signal strength, telemetry indicates that everything continues to operate nominally on the

surface of Mars, and both the Sagan Memorial Station and Sojourner rover continue to be in good health.

The rover wakeup song for Sol 79 was "Cashmere" by Led Zeppelin. The third time was truely the charm, as the rover was able to promptly position the APXS instrument onto the rock, Chimp. Composition data is currently be sent down to the Earth tomorrow before the rover moves off to its next target.

The Pathfinder spacecraft went to sleep prior to the Martian sunset which occurs at 4:30 AM PDT Tuesday morning. The lander should awaken at its usual time at 8AM local solar or Martian time tomorrow, and downlink should be received here on around 9 AM PDT.

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