The Mars Pathfinder Mission
Status Reports - Fourth Week

25 July 1997, 1:30 p.m. PDT

Mars Pathfinder celebrated its three-week anniversary on the surface of Mars today, with all spacecraft systems, science instruments and rover activities continuing to go exceptionally well.

On this Martian day, Sol 21, Earth rose at 10:48 p.m. PDT July 24 and Sunrise occurred at 1:53 a.m. PDT today.

The science team finished analyzing alpha proton X-ray spectrometer data from the rock nicknamed "Scooby Doo", the third rock measured by the rover since rolling off its ramp on July 5. ("Barnacle Bill" and "Yogi" were the first two rocks to be measured). "Scooby Doo", of interest to scientists because of its light color, has a chemical signature very similar to other soils measured at the Pathfinder landing site. However, initial analysis shows that it contains slightly higher amounts of calcium and silicon.

Data returned during successful communications sessions last night indicated that the lander and rover remain in excellent health, reported Guy Beutelschies, Pathfinder flight director for Sol 21.

Sojourner performed a "self-guided" traverse today, receiving a minimum of instructions from Earth before driving off to find its own way to the next rock. Up until now, Sojourner has relied on detailed instructions and "way points", or X-axis and Y-axis coordinates, to find its way to the next rock target.

Today's 3-meter (10-foot) excursion, however, involved only two sets of way point instructions and an additional command to "find the rock". Sojourner used its own hazard avoidance system to locate the two way points, as it usually does, but then relied only on its laser light beams to find the next rock and line up with it. By 11 a.m. PDT, Sojourner had stopped just 25 centimeters (10 inches) in front of "Souffle", the next rock to be studied.

The rover will begin making measurements of "Souffle" on Sol 22, using its alpha proton X-ray spectrometer.

Meanwhile, atmospheric and meteorological data on the temperatures and density of the Martian atmosphere continue to be received during daily telecommunications sessions. Data stored onboard Pathfinder last week, while the flight computer was automatically resetting itself, were returned on Sol 21.

The lander camera snapped images of the disturbed soil near the rock called "Lamb", and photographed three more rocks: "Half Dome", "Shark", and "Pumpkin".

The Earth set today -- Sol 21 -- at 12:24 p.m. PDT.
The Sun set at 2:46 p.m. PDT.

26 July 1997, 3:00 p.m. PDT

The Mars Pathfinder lander and rover remain healthy and are continuing to carry out science experiments on this Martian day, Sol 22.

Today the Earth rose over Mars at 11:28 p.m. PDT July 25.
The Sun rose today at 2:33 a.m. PDT.

Sojourner's self-guided journey to the rock "Souffle" was interrupted briefly by a software sequencing error, which was identified and corrected immediately. A sequencing error is easily corrected by modifying the numerical coding in the program responsible for executing the command, just as a computer user would modify coding in a program that runs the main menu or desktop functions of a personal computer.

"The problem was corrected immediately and a new sequence was radiated to the rover during the second downlink session", said Becky Manning, flight director for Sol 22. "By the end of that session, ground controllers had received confirmation that the rover had successfully received and was executing the instructions to continue its traverse to Souffle".

Sojourner will leave Souffle on Sol 23 and circumnavigate the lander. When that journey has been completed, the rover will be in the vicinity of three new rocks named "Baker Bench", "Desert Princess" and "Marvin".

The Mars Pathfinder lander imager (IMP) returned more data from the "insurance" panorama and "super" panorama today. It is preparing to take the standard end-of-the-day photograph of the rover before surface operations conclude in 30 minutes.

On Sol 22, the Earth set over Mars at 1:04 p.m. today.
The Sun will set in about 25 minutes, at 3:25 p.m. PDT.

27 July 1997, 4:30 p.m. PDT

All lander and rover systems and science instruments continue to operate well on Sol 23 of the Mars Pathfinder mission. Earth rise at the landing site occurred at midnight PDT July 26; sunrise followed at 3:13 a.m. PDT today.

In keeping with the tradition of playing wake-up songs for the space shuttle astronauts, the rover and flight teams were awakened on Sol 23 to the music of the Blues Brothers' version of "Raw Hide", a 1960s television western. The song was chosen to match "a long day of driving" for the rover.

Flight Director Jennifer Harris reported that start-of-the-day images showed the rover had begun to climb up the side of the rock named "Souffle", but was not able to position its science spectrometer against the rock. Consequently, no alpha proton X-ray spectrometer data were acquired today.

"However, this did not deter the rover from executing a long traverse which took it past the lander, through the 'Rock Garden', and past a rock named 'Casper', before coming to a stop near the rocks 'Desert Princess' and 'Baker's Bench'", Harris said. In all, Sojourner traveled six meters (nearly 20 feet) to complete the traverse, the longest excursion it has taken yet.

Images of the traverse, as well as routine beginning and end-of-day images, were taken by the Imager for Mars Pathfinder (IMP) camera. These images will go into a "rover movie", which is being compiled by the imaging team.

The IMP imaged sunrise on Mars, Phobos, one of Mars' two small moons, and the next portion of the super panorama, Harris said. The flight team also completed its downlink of the IMP stowed-position "insurance pan", which will enable them to begin downloading another portion of the super panorama.

Tomorrow's activities will include sending the rover to a way point beyond the rocks "Calvin" and "Hobbes". There it will be instructed to turn toward a rock named "Mini Matterhorn", take a picture of it, and then image the lander.

On this Martian day, Sol 23, the Earth set at 1:43 p.m. PDT, and the Sun set at 4:04 p.m. PDT.

28 July 1997, 3:00 p.m. PDT

The Mars Pathfinder lander and rover remain healthy and are continuing to carry out science experiments on this Martian day, Sol 24. Today the Earth rose over Mars at 12:48 am PDT July 28. The Sun rose today at 3:53 a.m. PDT.

The Sol 24 plan was executed without any problems. Sojourner moved past Souffle and made its way over 7 meters (almost 23 feet) to the rock called Mini Matterhorn. The Rover then imaged Mini Matterhorn and the lander.

The Imager for Mars Pathfinder (IMP) executed windsock, Phobos, dust opacity and star images in addition to cloud search and sunset images. The Super Panorama will continue to be downlinked to Earth.

29 July 1997, 4:30 p.m. PDT

Imaging the atmosphere of Mars -- how clear or dusty it is and whether there are traces of water vapor -- was the focus of science activities on the surface of Mars today.

The Mars Pathfinder imaging team also photographed the lander's wind socks, three small socks attached at different heights to a 1-meter mast. Visual images of these small socks provide scientists with information on wind strength and direction.

Temperatures on Sol 25 were typical, ranging from highs near minus 12 degrees Celsius (10 degrees Fahrenheit) and lows of minus 79 degrees Celsius (minus 110 degrees Fahrenheit). Today the Earth rose over Mars at 1:28 a.m. PDT and the Sun rose at 4:32 a.m. PDT.

The Atmospheric Science Instrument/Meteorology Package (ASI/MET) instrument team reported a very successful day of data return, said Flight Director Jennifer Harris, receiving more information than ever before on the pressure of the Martian atmosphere. Also included in the downlink sessions was more imaging data for the high-resolution "super panorama" of the landing site. In all, a total of 48 megabits of data was successfully returned.

A sequencing transmission error prevented the rover from executing its daily traverse, Harris said. The situation was quickly corrected and the rover was able to complete an accelerometer diagnosis sequence, which involved making a 120- degree turn in place. Sojourner will complete its traverse to the rock nicknamed Mini Matterhorn tomorrow and then turn to image the lander.

30 July 1997, 4:30 p.m. PDT

Pathfinder's 10.5-kilogram (23-pound) rover called Sojourner stalled today during the last stretch of its journey to a rock nicknamed Mermaid, but was quick to recover and prepare for completion of the traverse tomorrow.

Data returned this morning from the Sagan Memorial Station indicated that the rover's left front wheel stalled during the third of four waypoint maneuvers. Waypoints are navigational instructions -- consisting of x- and y-axis coordinates -- used by the rover to travel from one rock to another. To complete today's traverse to the rock nicknamed Mermaid, for instance, the rover had to make four short trips based on four sets of waypoint coordinates. Its wheel jammed during the third segment of the journey.

"This stall was probably caused by a small rock becoming jammed in one of the rover wheel's cleats", said Flight Director David Gruel. "Once the rover detected the stall on its own, she was able to autonomously clear the problem by backing up a short distance. Since the stall did not exist after the backup was performed, there's a high probability that Sojourner is ready to continue the drive around the lander tomorrow".

Approximately 55 megabits of engineering and science data were returned today. All data indicated the lander and rover are healthy and the lander's battery continues to power the craft through the subfreezing nights on Mars. The rover returned a "spectacular" image today of the rear of the lander and the rock nicknamed Mini Matterhorn.

Temperatures on Mars today ranged from a balmy minus 13 degrees Celsius (8 degrees Fahrenheit) at 5:35 p.m. local solar time to minus 79 degrees Celsius (minus 105 degrees Fahrenheit) at 5:30 a.m. local time. Winds were light and from the west.

On this Martian day, Sol 26, Earthrise occurred at 2:09 a.m. PDT, and sunrise followed at 5:12 a.m. PDT. The Earth later set at 3:43 p.m. PDT, and Pathfinder will observe its 26th sunset at 6 p.m. PDT.

31 July 1997, 4:30 p.m. PDT

The Mars Pathfinder flight team has completed all of its science and engineering goals, four days before the primary mission draws to a close, said Dr. Matthew Golombek, Pathfinder project scientist, at today's press briefing.

Atmospheric-surface interactions were the focus of today's presentation. To set the stage, Dr. Mark Lemmon, a member of the Imager for Mars Pathfinder (IMP) camera team from the University of Arizona, presented new images of the Martian sunrise and sunset. True to color, the dawn images revealed pale pink sunrises and clouds floating overhead. The reddish tint is the result of Martian dust, composed of oxidized iron, which is present in the atmosphere. The sunset images -- color-enhanced to bring out structural detail in the atmosphere -- showed a sky darkening to salmon-colored hues.

These spectacular images of the Martian summer are possible by return of an unprecedented amount of science and engineering data -- on the order of 400 megabits just in the last nine days -- Golombek pointed out.

Temperature highs and lows at the landing site have not varied much, said Dr. Robert Haberle, a participating scientist from the NASA Ames Research Center. They range from highs of about minus 12 degrees Celsius (8 degrees Fahrenheit) to lows near minus 76 Celsius (minus 105 Fahrenheit).
Frozen water-ice clouds are evident in the Martian sky during the early morning hours, but evaporate once temperatures rise. "We expect late night and early morning clouds, but we expect those clouds will burn off fairly rapidly with sunrise, giving way to a dusty Martian day", Haberle said.
Although there has not been much variation in these weather conditions since Pathfinder arrived, they are expected to begin changing in about a month, as fall arrives and ushers in the dust storm season.

Atmospheric pressures, on the other hand, are fluctuating dramatically, sometimes peaking two, three or four times a day, Haberle noted. Pressure oscillations are indicative of a global scale thermal tidal system that is moving dust, water-ice or vapor clouds and other volatiles through the atmosphere. On Mars, these atmospheric variations are sizable, whereas on Earth they almost never occur.

Since data-gathering began, the maximum change in pressure over the course of a day has been 0.3 millibars, which is about 4.5 percent of the average pressure on Mars. On Earth, pressures that low might occur during a severe hurricane. A better understanding of these pronounced pressure oscillations will help scientists understand the processes by which volatiles enter and escape the Martian atmosphere, and may shed more light on the rise of regional and global dust storms.

Wind speeds have been increasing with altitude, reported Dr. Robert Sullivan of Arizona State University. And temperatures will vary dramatically with elevation. When ground temperatures are 16 to 21 degrees Celsius (60 to 70 degrees Fahrenheit), they can drop to minus 23 to 27 degrees Celsius (minus 10 to minus 15 degrees Fahrenheit) just five and a-half feet above the ground.

Images of the Martian landscape also revealed a shiny object about 1,200 meters (7/10ths of a mile) away from the lander. Dr. Michael Malin, a participating scientist, said the object is about the same dimensions and is probably the spacecraft's discarded backshell, which separated just before the spacecraft landed.

Although the Pathfinder lander and rover remain healthy, engineers plan to recharge the lander's battery during a two-day hiatus beginning Sunday, Aug. 3. The lander will perform some science experiments during the day, but will use most of its solar energy to charge the battery.
At night, the craft essentially goes to sleep.

The rover will continue its daily traverses and spectrometer studies, rolling off to a smooth, dark region of soil called Mermaid Dune, tomorrow. After taking measurements of the soil, scientists will identify one of three large, dust-free rocks -- Shark, Half Dome, and Wedge -- as the next target for study.

On this Martian day, Sol 27, Earthrise occurred at 2:49 a.m. PDT, and sunrise followed at 5:52 a.m. PDT. The Earth later set at 4:23 p.m. PDT and the Sun set at 6:41 p.m. PDT.


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Status reports prepared by:
Office of the Flight Operations Manager
Mars Pathfinder Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109


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EDT = PDT + 3 hrs. = UTC - 4 hrs. Venezuelan Time = UTC - 4:30 hrs.

Updated: August 4 '97

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