Although yesterday's silence was planned, the silence from Monday is still unexplained. Today's data may shed some light on the period of silence. Limited DSN availability forced us to take a break from operations. Very early on Saturday morning Sojourner will attempt to get closer to Shark for an APXS measurement. Shark will soon join Yogi and Barnacle Bill in the annals of rocks that have been analyzed for content by the Alpha Proton X-Ray Spectrometer, or APXS.

On Monday, the flight team transmitted commands to activate the Mars Orbiter Camera science instrument in preparation for two days of star imaging this week. Once per day on Wednesday and today, the spacecraft turned to point the camera at stars in the constellation Scorpius called Beta Scorpii, Omega-1 Scorpii, and Omega-2 Scorpii. Over the course of one hour on each imaging day, the camera observed stars within the target area.

The camera team, led by Dr. Michael Malin, will use these star images to determine the best focus settings for a set of long-range Mars images that will be obtained during a three-day period beginning on Tuesday, August 19th. In addition, the Thermal Emission Spectrometer science instrument will also observe Mars during this time period.

After a mission elapsed time of 281 days from launch, Surveyor is 226.68 million kilometers from the Earth and is moving in an orbit around the Sun with a velocity of 21.80 kilometers per second. This orbit will intercept Mars 27 days from now, slightly after 6:00 p.m. PDT on September 11th (01:00 UTC, September 12th). The spacecraft is currently executing the C10 command sequence, and all systems continue to be in excellent condition.

Sojourner, meanwhile, did what she was supposed to do when confronted by obstacles beyond her operating capability: she stopped and waited patiently for instruction. With her front wheel on the rock Torres and rear wheel on Tigger, her articulation hazard parameter was exceeded. This caused her further motion toward the rock Shark to be stopped, as provided for in the rover software. Rover engineers are considering a change in the value of this articulation hazard parameter to allow Sojourner freer motion in the challenging terrain of the Rock Garden. A decision for this change will be made in the next couple of days.

A total of 50 megabits of data were returned from the surface of Mars in a two hour transmit session to the Goldstone antenna in California. Earthset on Mars was at 1:35 a.m. PDT and sunset was at 3:30 a.m.

For the first time, a "thinking" robot, equipped with sophisticated laser eyes and automated programming, is "thinking" and reacting to unplanned events on the surface of another planet.

"After a few days on the Martian surface, when we left the rock named Yogi, we turned on Sojourner's hazard avoidance system and asked it to start making some of its own decisions," said Brian Wilcox, supervisor of the robotic vehicles group at JPL. "This hazard avoidance system sets the rover apart from all other machines that have explored space. Sojourner had to make that trip to the next rock without the benefit of detailed information to warn it of obstacles along the way."

Sojourner's intelligence is the product of many years of research in the fields of telerobotics and automation. Beyond the challenges of building a robot that can survive the frigid climate of another planet, Sojourner is taking the robotic exploration program one step further to a day when truly "smart" machines will be able to explore hundreds of kilometers away from a landing site all on their own.

"Because Sojourner is our first rover, we designed it to be quite safe," Wilcox said. "She moves slowly (0.7 centimeter per second or 0.3 inches per second) and stops a lot along the way to sense the terrain and process information. Her IQ is probably not as high as an insect's, but to put it in the proper perspective, consider that even a house fly has more computing capacity than the largest supercomputers today."

Sojourner's hazard avoidance system is comprised of five laser stripes that project out to the ground. One laser is located in the center of the rover body and points straight ahead. Two of the laser beams are pointed outward at a modest angle from the center beam, while two more project much farther outward, like periphery vision, beyond the rover's body.

"These lasers cut across anything in the rover's path," Wilcox said. "By looking at the shape of the stripe with the rovers cameras, we can detect rocks and build contour maps of the terrain immediately in front of the rover. The rover then moves three inches ahead and projects its laser beams on the ground again. We take that data and continue to build our terrain maps based on the shapes of the laser beams as they bend with the shape of the ground."

To complement its laser eyes, the rover has three levels of autonomy to use in choosing its path across the Martian sand. The first level involves little risk: it instructs the rover simply to avoid all but the flatest ground. The higher levels of risk cause the rover to drive over bigger and bigger obstacles without trying to avoid them, with the highest risk level allowing the rover to climb over rocks almost as big as the wheels.

"If we were exploring a dry riverbed, which would be relatively smooth and devoid of rocks, the first level of risk would probably be all we needed to drive a rover," Wilcox said. "But given the terrain we've landed in, which contains a huge variety of rocks, we have to use the higher levels of risk. Just like on the freeway, you would always drive around any small object if you could. In more rugged terrain, we don't have that luxury."

Another type of autonomy command tells the rover to find rocks.

"We tested this mode when Sojourner made its way to the rock named Souffle," Wilcox said. "We gave it only the x- and y-axis coordinates, then told it to find a rock. It used its laser hazard sensor to find, instead of avoid, the rock. If the coordinates were about right, then it knew it must be at the right rock. And even though the wheel slippage and gyro drift would have caused the rover to be more than 30 centimeters (1 foot) away from Souffle, the rover instead parked itself within 4 centimeters (2 inches) of the spot we wanted near the rock."

Sojourner's intelligence is based on a mathematical model that emulates animal behavior. The ability for animals to avoid or flee danger, such as predators, is a low level reflex, Wilcox explained, but it gets the job done. "The rover can distinguish between obstacles that pose no threat, such as a two- or three-inch-tall rock that can be driven over, as opposed to a 10- or 12-inch-tall rock that might tip it over," he said. "As soon as the rover recognizes the hazardous rocks, it switches into the hazard avoidance behavior and begins to turn until it no longer sees the obstacle. Then it moves forward and returns to a course toward the current goal."

Sojourner's reasoning capabilities deviate from the strict sequence of instructions used on prior space explorers. Previous spacecraft have operated solely using sequences of instructions created by human operators on the ground, along with preprogrammed "safing" sequences which protect the spacecraft from harm and re-establish contact with Earth if some failure should occur. Sojourner has both of these capabilities, but also has reflexes to avoid hazards and respond to unplanned events. This is necessary because it would go much too slow if humans on Earth had to make every decision when interacting with the unknown environment.

"This is what allows Sojourner to take a stroll on its own," Wilcox said. "If it encounters new rocks that it had not anticipated, the rover will use sensory information provided by the lasers to circumvent the obstacle. If the wheels on one side slip in the dirt, it will begin to turn until it is going back in the right direction."

Sojourner's major limitations lie in its dependence on the Pathfinder lander for communications. If it journeys much beyond the lander's line of sight, it will become marooned. Already on the drawing boards for future missions are rovers that will be able to communicate with orbiters flying overhead a landing site. Engineers hope to gain a much better understanding of Sojourner's interactions in the Martian environment to make this concept a reality.

"We are already learning a lot about the demands of driving a rover," Wilcox said. "Right now we're developing a brand new command sequence for the rover every day, but we're accomplishing that with significantly fewer people than we did in the Voyager days. In those days, it took as many as 700 people to fly the spacecraft, whereas Sojourner only requires about seven people."

Powerful visualization tools not yet invented 20 years ago have also advanced Sojourner's and future rovers' autonomous capabilities. For instance, with a specially designed computer program, stereo images taken by the lander or Sojourner are integrated into a three-dimensional view of the rover's location. Engineers can see the rover's tire tracks and know where it has gone. Their view of the immediate surroundings also helps them decide where Sojourner should go next.

"In 10 to 20 years, I'd like to see a rover that could go anywhere on Mars," Wilcox said. "I'd like to launch a Lewis and Clark expedition, where we would basically travel 1,000 kilometers cross-country with our rover."

Even in the shorter term, though, the strides made by Sojourner's travels on Mars will be evident. The next rovers to explore the red planet will have at least 1,000 times the processing speed of Sojourner and will be able to travel much farther much faster.

"Tomorrow's rover will be able to plan and think ahead," Wilcox said. "Whereas Sojourner can only plan 20 centimeters ahead, our next rover will be able to plan 10 meters or more ahead. And while Sojourner has no concept of what rocks look like 20 meters away, her successor will be able to recognize rocks that far away very easily."

After Earthrise yesterday at 10:50 a.m PDT, Sol 39 the Sojourner woke up to a song written especially for the occasion: "Mars Rovin'" by Tempus Fugit and the Time Travellers (click here for a full listing of all Rover wake-up songs to date). Even though there were problems with the articulation of the rover during this sol, it performed its operations with remarkable results. Sojourner pushed the rock Hassock out of her way, but a fault resulted when another wheel moved up onto a medium-sized rock. This caused further movement to cease for safety reasons and as provided for in the rover's software. The Rover will continue its journey toward the rock named Shark when operations resume.

The Imager for Mars Pathfinder (IMP) returned more images including night observations of the skies above the Sagan Memorial Station. Possible images of stars may be among those received on Earth, but will require further analysis. The "Super Panorama", a full 360-degree image of the landing site in all 12 spectral filters from both eyes of the IMP, is now halfway complete. The imaging team expects the entire panorama to be received by Earth in the next two weeks.

Meanwhile, the battery provided more than enough power for all night-time operations of the lander, but the station was placed in hibernation mode tonight to conserve power.

Mars Pathfinder Mission Report
JPL - 11 August 1997 - Continuing the healthy and normal operations of the lander and rover on the surface of Mars, yesterday was a busy sol.

After sunrise yesterday, Sol 38, at 9:30 am Pacific Daylight Time, the lander woke up and began its daily round of atmospheric opacity measurements, imaging of the surrounding terrain, weather measurments and other activities. The Imager for Mars Pathfinder (IMP) returned a total of 65 megabits of information in a marathon 5 hour transmit session made possible by the conservation of battery power during the Martian night. This saving of energy allows power to be used to transmit data back to Earth in place of recharging the battery.

Sojourner moved off the rock Hassock and turned to place its Alpha Proton X-Ray Spectrometer (APXS) on the rock Wedge. It was not immediately clear whether this operation was completely successful and if the APXS was placed on the rock or on the soil surrounding it. Today will be a rest day for the rover and an assessment day for the team back here on Earth. In any case, the rover will continue with its operations in the Rock Garden and its explorations of the interesting features to be found there.

The Earth set on Mars at 11:00 pm PDT and sunset was at 1:00 am PDT.

Pathfinder Concludes Primary Mission
August 10, 1997 - NASA's Mars Pathfinder spacecraft -- a novel mission to send an inexpensive lander and roving prospector to the surface of Mars - has concluded its primary mission, fulfilling all of its objectives and returning a wealth of new information about the red planet.

The robotic lander, which continues to explore an ancient outflow channel in Mars' northern hemisphere, completed its milestone 30-day mission Aug. 3, capturing far more data on the atmosphere, weather and geology of Mars than scientists expected. In all, Pathfinder returned 1.2 gigabits (1.2 billion bits) of data and 9,669 tantalizing pictures of the Martian landscape.

The mission has been followed with great interest via the World Wide Web. Twenty Pathfinder mirror sites, constructed by JPL web engineer Kirk Goodall and managed by Pathfinder webmaster David Dubov, recorded 565,902,373 hits worldwide during the period of July 1 - August 4. The highest volume of hits in one day occurred on July 8, when a record 47 million hits were logged, which is more than twice the volume of hits received on any one day during the 1996 Olympic Games in Atlanta.

"The data returned by the Sagan Memorial Station and Sojourner has been nothing short of spectacular, and it will help provide a scientific basis for future Mars missions, including a sample return, for years to come," said Dr. Wesley Huntress, NASA associate administrator for space science. "The Pathfinder team's 'can do' attitude not only was critical to overcoming several complex technical challenges during development and cruise, but has carried through the uncharted territory of operating a solar-powered lander and mobile rover on the surface of a planet millions of miles from Earth."

"This mission demonstrated a reliable and low-cost system for placing science payloads on the surface of Mars," said Brian Muirhead, Mars Pathfinder project manager at NASA's Jet Propulsion Laboratory. "We've validated NASA's commitment to low-cost planetary exploration, shown the usefulness of sending microrovers to explore Mars, and obtained significant science data to help understand the structure and meteorology of the Martian atmosphere, and to understand the composition of the Martian rocks and soil."

A new portrait of the Martian environment has begun to emerge in the 30 days since Pathfinder and its small, 10.5- kilogram (23-pound) rover began to record weather patterns, atmospheric opacity and the chemical composition of rocks washed down into the Ares Vallis flood plain. The rover's alpha proton X-ray spectrometer, led by Principal Investigator Dr. Rudolph Rieder, was responsible for making the first in-situ measurements of rocks near the landing site.

"We are seeing much more differentiation of volcanics than we expected to see," said Dr. Matthew Golombek, Mars Pathfinder project scientist at JPL. "The high silica content of one of the rocks we've measured suggests that there was more crustal activity - heating and recycling of materials -- early in Mars' history than we thought."

Similarly, atmospheric-surface interactions, measured by a meteorology package onboard the lander, are confirming some conditions observed by the Viking landers 21 years ago, while raising questions about other aspects of the planet's global system of transporting volatiles such as water vapor, clouds and dust, said Science Team Leader Dr. Timothy Schofield. The meteorology mast on the lander has observed a rapid drop-off in temperatures just a few feet above the surface, and one detailed 24-hour measurement set revealed temperature fluctuations of 30-40 degrees Fahrenheit in a matter of minutes.

In addition, sweeping, color panoramas of the Martian landscape, created by the Imager for Mars Pathfinder (IMP) team and Principal Investigator Peter Smith, are revealing clear evidence that the surface of Mars has been altered by winds and flowing water.

The rover's performance has easily surpassed its designers' minimum expectations. Engineers designed the roving vehicle's electronics, battery power and hazard avoidance features to see it through at least a week of safe roving, not knowing beforehand what conditions it might encounter on Mars. After 30 days, the rover is still healthy and has clocked 52 meters (171 feet) distance, circumnavigated the lander and taken 384 spectacular views of rocks and the lander.

"Sojourner's capabilities to detect hazards and then act on its own to overcome those hazards has been remarkable," said Dr. Jacob Matijevic, Sojourner project manager. "The technology experiments we have been able to perform with the rover's wheels have given us more information about the composition of the Martian soil, as well as rocks around the landing site. Sojourner's durability in this frigid, hostile environment is also showing us that we are on the right track to building smarter, even more durable rovers for future missions."

Pathfinder's primary objective was to demonstrate a low-cost way of delivering an instrumented lander and free-ranging rover to the surface of the red planet. Landers and rovers of the future will share the heritage of spacecraft designs and technologies tested in this "pathfinding" mission.

Part of NASA's Discovery program of low-cost planetary missions with highly focused science goals, the spacecraft used an innovative method of directly entering the Martian atmosphere. Assisted by an 11-meter (36-foot) diameter parachute, the spacecraft descended to the surface of Mars and landed, using airbags to cushion the impact.

This novel method of diving into the Martian atmosphere worked like a charm. "Every event during the entry, descent and landing (EDL) went almost perfectly," said Richard Cook, Pathfinder mission manager. "The sequences were executed right on time and well within our margins."

Pathfinder landed right on the money, within 20 kilometers (13 miles) of the targeted landing site. The landing site coordinates in Ares Vallis were later identified as 19.33 degrees north latitude, 33.55 degrees west longitude.

The spacecraft's terminal velocity as it parachuted to the ground was higher than expected, said Rob Manning, Pathfinder flight system chief engineer. "Interestingly, we estimated our descent on the parachute at about 60 meters per second (134 miles per hour). Software controlling the retro rockets recorded Pathfinder's speed at about 61.5 meters per second (140 miles per hour) at the time the RAD (rocket-assisted deceleration) rockets fired."

Pathfinder's performance in the Martian atmosphere will be of great value to Mars Global Surveyor, which will aerobrake through the Martian atmosphere to circularize its orbit when it reaches Mars on Sept. 11. The Pathfinder navigation team, led by Peter Kallemyn of JPL, estimated horizontal wind velocities in the upper atmosphere, which accelerated the spacecraft's descent velocity by about 13 meters per second (20 to 25 miles per hour).

After being suspended from a 20-meter (65-foot) bridle and firing its retro rockets, a 5.8-meter (19-foot) diameter cluster of airbags softened Pathfinder's landing, marking the first time this airbag technique has been used. The spacecraft hit the ground at a speed of about 18 meters per second (40 miles per hour) and bounced about 16 times across the landscape before coming to a halt. The airbag seems to have performed perfectly and sustained little or no damage. To top it off, the spacecraft even landed on its base petal, consequently allowing its thumb- sized antenna to communicate the successful landing to a jubilant team on Earth only three minutes after touch down.

Science data from the surface of Mars will continue to be collected and transmitted to Earth, then analyzed by scientists, as Pathfinder enters its extended mission. The lander was placed in a two-day hibernation period to recharge its battery after the conclusion of the primary mission, and the flight team will begin to power the lander battery off each Martian night now to conserve energy. The rover's batteries remain in good condition, but are not rechargeable.

Mars Pathfinder Mission Report
August 4, 1997 - Although the reason for yesterday's loss of downlink opportunities has not yet been identified, science activities proceeded normally today on the surface of Mars. Today, Sol 30, marks the end of the Mars Pathfinder primary mission, 30 days after the spacecraft landed in an ancient outflow channel called Ares Vallis.

The Imager for Mars Pathfinder (IMP) continued to image the thin Martian atmosphere, the lander's wind socks, the Sun and the rover as it roamed to another destination, said Carl Steiner, Mars Pathfinder flight director. Acting as a weather station, the Pathfinder lander -- now called the Sagan Memorial Station -- gathered weather data for the 12th consecutive day. Data from yesterday's surface operations had been stored onboard the lander and were downlinked today. Highs on Mars rose to minus 10 degrees Celsius (14 degrees Fahrenheit) today and dipped to minus 70 degrees Celsius (minus 94 degrees Fahrenheit).

The rover finished its soil analysis of Mermaid Dune before heading toward the Rock Garden. An onboard tilt protection circuit caused the rover to shut down after reaching 10 centimeters (0.3 feet) of motion.

"An especially noisy accelerometer had caused this problem in past, but had successfully guarded the rover against excessive tilt," Steiner said. "The rover team thought it prudent to activate this device, even with the possibility of inadvertent shut-down, because of the uneven path to the Rock Garden and the long traverse." Sojourner will resume this traverse on Sol 32, as Pathfinder's extended mission gets under way.

Three downlink sessions were successfully carried out today using the low-gain antenna once and the high-gain antenna for the next two sessions, Steiner said. The operations team, however, was unable to complete its planned downlink of an eighth (octant) of the so-called "super pan" before the end of the day and the beginning of a two-day sleep period for the lander.

"This will be the first time in nearly 240 days that the lander's electronics will be powered off," Steiner said. "At the conclusion of today's activities, all lander electronics, with the exception of a few computer chips that comprise the hybernate circuit, will be powered off to conserve energy through the Martian evening and prolong our waning battery."

The hybernate circuit has been programmed to wake up the lander at 7:30 a.m. local solar time tomorrow. A backup circuit will wake the lander at 8 a.m. if the lander is still asleep. Tomorrow's activities will focus on recharging the battery to the fullest capacity possible. No science experiments are planned.

On this Martian day, Sol 30, Earthrise occurred at 4:49 a.m. PDT and sunrise occurred at 7:51 a.m. PDT. The Earth set over the landing site at 6:22 p.m. PDT and the sun set at 8:39 p.m. PDT.

Mars Pathfinder Mission Report
August 2-3, 1997 - Mars Pathfinder lander and rover operations were curtailed August 2 when the lander downlink session, scheduled to begin at 1:20 p.m. PDT, was not initiated. The cause of the problem was not known at the time, said Mars Pathfinder Mission Manager Richard Cook.

The flight team, led by Flight Director Carl Steiner, subsequently reestablished communications with the lander and received a brief carrier blip at 3:30 p.m. PDT. Additional downlink sessions were not attempted, however, because of the lack of time before the Earth set over the landing site at 5:42 p.m. PDT.

Data on the health of the lander and rover, in addition to other engineering telemetry, were acquired the following day.

On this Martian day, Sol 29, Earthrise occurred at 4:09 a.m. PDT and sunrise followed at 7:11 a.m. PDT. The sun set over the landing site at 7:59 p.m. PDT.

Although yesterday's loss of downlink opportunities has not yet been identified, science activities proceeded normally today, August 3, on the surface of Mars. Today, Sol 30, marks the end of the Mars Pathfinder primary mission, 30 days after the spacecraft landed in an ancient outflow channel called Ares Vallis.

The Imager for Mars Pathfinder (IMP) continued to image the thin Martian atmosphere, the lander's wind socks, the Sun and the rover as it roamed to another destination, said Carl Steiner, Mars Pathfinder flight director. Acting as a weather station, the Pathfinder lander -- now called the Sagan Memorial Station -- gathered weather data for the 12th consecutive day. Data from yesterday's surface operations had been stored onboard the lander and were downlinked today. Highs on Mars rose to minus 10 degrees Celsius (14 degrees Fahrenheit) today and dipped to minus 70 degrees Celsius (minus 94 degrees Fahrenheit).

The rover finished its soil analysis of Mermaid Dune before heading toward the Rock Garden. An onboard tilt protection circuit caused the rover to shut down after reaching 10 centimeters (0.3 feet) of motion.

An especially noisy accelerometer had caused this problem in past, but had successfully guarded the rover against excessive tilt, Steiner said. The rover team thought it prudent to activate this device, even with the possibility of inadvertent shut-down, because of the uneven path to the Rock Garden and the long traverse Sojourner will resume this traverse on Sol 32, as Pathfinder's extended mission gets under way.

Three downlink sessions were successfully carried out today using the low-gain antenna once and the high-gain antenna for the next two sessions, Steiner said. The operations team, however, was unable to complete its planned downlink of an eighth (octant) of the so-called super pan; before the end of the day and the beginning of a two-day sleep period for the lander.

This will be the first time in nearly 240 days that the lander's electronics will be powered off, Steiner said. At the conclusion of today's activities, all lander electronics, with the exception of a few computer chips that comprise the hybernate circuit, will be powered off to conserve energy through the Martian evening and prolong our waning battery.

The hybernate circuit has been programmed to wake up the lander at 7:30 a.m. local solar time tomorrow. A backup circuit will wake the lander at 8 a.m. if the lander is still asleep. Tomorrow's activities will focus on recharging the battery to the fullest capacity possible. No science experiments are planned.

On this Martian day, Sol 30, Earthrise occurred at 4:49 a.m. PDT and sunrise occurred at 7:51 a.m. PDT. The Earth set over the landing site at 6:22 p.m. PDT and 8:39 p.m. PDT.

Mars Pathfinder Mission Report
August 1, 1997 - A wealth of new information about Martian weather and atmosphere was acquired by the Pathfinder lander on the 27th and 28th days of surface operations in the Ares Vallis outflow channel on Mars.

Data are showing that daily temperatures do not vary much, but minute-by-minute temperatures can fluctuate dramatically, reported Flight Director Rob Manning. Atmospheric pressures can also change significantly within a matter of minutes. Scientists think some of these variations may be caused by small dust devils that can be whipped up by a gust of wind.

The flight team has been taking advantage of longer downlink sessions over the last several Martian days to acquire as much weather data as possible. Regular weather measurements will be limited in the days ahead due to the lander's limited battery power. A two-day shutdown of lander operations to recharge the battery will occur on Sunday and Monday, Aug. 3-4.

Summer temperatures remain in the same range. This morning's low was minus 75 degrees Celsius (minus 103 degrees Fahrenheit) , while highs rose to minus 15 degrees Celsius (5 degrees Fahrenheit). Winds were blowing lightly from the south and swinging around from the northwest during the day.

The rover continued its trek south today after undergoing a temporary delay. Yesterday the vehicle detected a jam in its left front wheel and autonomously backed up to free the pebble from the cleats in its stainless steel wheels. Today Sojourner marched about 4 meters (13 feet) to the south.

"Using waypoints specified the day before, Sojourner stopped, spun about and carefully backed up and onto a small dune named Mermaid today," Manning said. "This afternoon she continued to back up onto the dune and then lowered the alpha proton X-ray spectrometer onto the dune. Tonight the rover will collect elemental spectra of this interesting feature."

The lander and rover returned more than 60 megabits of science and engineering data on Sols 27 and 28. "This data included yet another rover traverse movie and a series of photometric strips that will allow scientists to precisely gauge the optical properties of key features near the lander," Manning added.

On this Martian day, Sol 28, Earthrise occurred at 3:29 a.m. PDT and sunrise followed at 6:32 a.m. PDT. The Earth set at 5:02 p.m. PDT and sunset occurred at 7:20 p.m. PDT.

Mars Pathfinder Mission Report
July 31, 1997 - 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.

Mars Pathfinder Mission Report
July 30, 1997 - 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.

Mars Pathfinder Mission Report
July 29, 1997 - 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.

The Earth set today at 3:03 p.m. PDT and the Sun will set at 5:22 p.m. PDT.

Mars Pathfinder Mission Report
July 28, 1997 - 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.

Mars Pathfinder Mission Report
July 27, 1997 - The Mars Pathfinder lander and rover remain healthy and are continuing to carry out science experiments on this Martian day, Sol 23. Today the Earth rose over Mars at 12:00 midnight PDT July 27. The sun rose today at 3:13 a.m. PDT.

The beginning of day rover image showed that Sojourner had climbed slightly up Souffle and therefore the Alpha Proton X-Ray Spectrometer did not make contact with the rock. No APXS data was acquired from Souffle.

However, the rest of the Sol 23 plan was executed flawlessly. Sojourner began its circumnavigation of the lander, moving through the Rock Garden, past the rock dubbed Casper, and ending near the group of rocks named Desert Princess and Baker's Bench. This traverse involved almost 6 meters (18 feet) of autonomous driving for the Rover, far more than any previous sol's activity.

The Imager for Mars Pathfinder (IMP) executed sunrise, Phobos, opacity and star images in addition to the next sector of the "Super Panorama". The team has also successfully completed the downlink of the IMP stowed-position "Insurance Panorama". The Super Panorama will now begin to be downlinked to Earth.

Monday's plans are to allow the Rover to continue driving to a way-point beyond Calvin and Hobbes and then turn toward the rock called Mini-Matterhorn. Sojourner will then image this rock and the Sagan Memorial Station.

On Sol 23, the Earth set over Mars at 1:43 p.m. today. The sun set at 4:04 p.m. PDT.

Mars Pathfinder Mission Report
July 26, 1997 - 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.

Mars Global Surveyor
Friday, 25 July 1997 - As of today, less than seven weeks remain until arrival at Mars. Over the past two weeks, the flight team has spent the majority of their time preparing for this arrival by conducting operational simulations, finalizing operational plans, and modifying Surveyor's onboard flight software.

Two simulations were conducted on July 17th and July 24th. These exercises were designed to train flight team members and tracking antenna operators of the Deep Space Network to react to time-critical situations that will occur during aerobraking. In this phase of the mission, the flight team will lower the high point of Surveyor's orbit from 56,000 to 400 km by repeatedly flying the spacecraft through the upper Martian atmosphere. Each exercise provided an opportunity for the team to analyze spacecraft telemetry from a simulated atmospheric pass, and to use the analysis toward generating new commands for the next pass.

In addition to the operational simulations, the flight team made two different modifications to Surveyor's onboard flight software. The first one involved reprogramming the payload data subsystem to collect information packets from the science instruments at a slightly faster rate. This improvement in efficiency will allow the camera and Thermal Emission Spectrometer to increase their combined volume of scientific data transmission by about 10%.

The second of the two software modifications will allow Surveyor's flight computer to automatically activate gyroscope #2 in the unlikely event that an anomalous condition is detected in either the #1 or #3 gyros. Normally, all three gyroscopes are active during flight to help the spacecraft keep track of its pointing orientation in space. However, because only two gyroscopes are required at any one time, project management has decided to save the #2 gyro for use as a backup in emergency situations.

After a mission elapsed time of 260 days from launch, Surveyor is 201.83 million kilometers from the Earth, 11.76 million kilometers from Mars, and is moving in an orbit around the Sun with a velocity of 21.77 kilometers per second. This orbit will intercept Mars 48 days from now, slightly after 6:00 p.m. PDT on September 11th (01:00 UTC, September 12th). The spacecraft is currently executing the C9 command sequence, and all systems continue to be in excellent condition.

Mars Pathfinder Mission Report
July 24, 1997 - All communications sessions between the Pathfinder lander and rover were successfully completed today, one day short of the mission's three-week anniversary on the surface of Mars.

Sol 20 began when the Earth rose over Mars' horizon at 10:30 p.m. Pacific Daylight Time last night (July 23), enabling the flight team to initiate communications with the spacecraft. The Sun later rose at 1:15 a.m. PDT this morning, supplying the lander and rover with the energy needed to carry out specific tasks.

Communications were carried out using the 70-meter (230- foot) antenna of NASA's Deep Space Network facility in Madrid, Spain. Forty-seven megabits of data during two downlink sessions were returned on Sol 20.

The data indicated that both the lander and rover remain in excellent health and are continuing to operate masterfully. Flight Director Dave Gruel reported that no further flight software resets have occurred since the team sent modified flight software three sols, or days, ago.

Today's data included numerous images taken for ongoing science experiments. The Imager for Mars Pathfinder (IMP) also completed another section of the 12-color super panorama image of the landing site, then imaged the rover to add to an ongoing "rover movie" that is being assembled. IMP took a final, end-of- the-day photo of Sojourner following completion of its activities.

Sojourner traveled a total of 7/10ths of a meter (2.3 feet) today and performed another soil mechanics experiment that involved staging a "wheely." The last of its activities was to lower the alpha proton X-ray spectrometer onto the soil near the rock named Lamb. Presently, because it is night on Mars, the rover is powered down and using only its battery to operate the spectrometer and gather data on the Martian soil near Lamb. That data will be transmitted to Earth via the lander during the next Martian day, Sol 21, which begins when Earth rises over Mars tonight at 8:48 p.m. PDT.

Activities for Sol 21 will include another rover soil mechanics test, some more autonomous driving and repositioning of Sojourner's spectrometer against the side of Lamb in preparation for data-gathering the following night.

The lander's meteorological experiment reported highs today of minus 2 degrees Celsius (28 degrees Fahrenheit) and morning low temperatures of minus 73 degrees Celsius (minus 99 degrees Fahrenheit). The weather detectors also recorded large fluctuations of 3/10ths millibars in total pressure on the surface of Mars.

On this Martian day, Sol 20, the Earth set at 11:45 a.m. PDT, ending spacecraft communications with Earth for the day. The Sun set at 1 p.m. PDT.

More than 300 megabits of data have been returned just in the last week, said Dr. Matthew Golombek, Pathfinder project scientist. The rover continues to follow an aggressive series of maneuvers to study rocks and soils identified by the science teams for their interesting features. In addition, the rover's wheel tracks and soil abrasion experiments are beginning to yield new information about the Martian soil, which appears to be finer than talcum powder.

Worldwide interest in the mission has peaked, with more than 400 million hits reported on the Internet to date, said Kirk Goodall, Mars Pathfinder web engineer. Goodall and David Dubov, Mars Pathfinder webmaster, constructed 20 Pathfinder mirror sites prior to landing day to service the public. The most hits received in a single day -- 47 million -- occurred on July 8, Goodall said, which is more than double the number of hits received in a single day during the 1996 Olympic Games in Atlanta, Georgia.

A communications problem experienced last weekend has been resolved, reported Richard Cook, Mars Pathfinder mission manager. The problem was associated with ground operations, which has been required to reconfigure equipment and software on a daily basis, and the necessity of establishing communications links only during the short periods of time each day when the lander's transmitter is on.

Scientists are beginning to learn more about the Martian soil by studying the rover's wheel tracks, asking it to perform soil abrasion experiments and measuring the material properties of dust and soil through these wheel-soil interactions. Dr. Henry Moore, a rover scientist with the U.S. Geological Survey in Menlo Park, CA, likened the Martian soil to a very fine-grained silt that could be found in Nebraska. The Martian particles are less than 50 microns in diameter, which is finer than talcum powder.

Dust coverage on some of the spacecraft instruments is accumulating at a very low rate of about 3 percent per day, added Dr. Geoffrey Landis, NASA Lewis Research Center in Cleveland, which is very close to the team's original predictions. These measurements also indicated that the dust was not moving toward the Martian poles right now. Additional study of dust patterns in the Martian environment may shed more light on the ways in which dust leaves the Martian atmosphere.

Dr. Peter Smith, University of Arizona, who is principal investigator of the lander camera, described more about the Martian landscape, pointing out a shallow riverbed crossing through the landing site and rocks in the distance that were washed into this outflow channel from the Martian highlands. About four distinct impressions left by the airbags were evident in the images presented today, noted Dr. Tim Parker, a science team member at JPL. The disturbed soil suggested that the spacecraft was nearly rolling, rather than bouncing, by the time it came to a stop. Parker estimated that the spacecraft bounced 15 to 20 times over a kilometer (6/10ths of a mile) of the landing site before stopping.

Science activities last night took the rover through the "cabbage patch," an area of soil in between Scooby Doo and a light-colored rock named Lamb. The rover will conduct a soil experiment, then turn and move toward Lamb. Scientists will take measurements of the dark soil near that rock before moving Sojourner close enough to place its spectrometer against the rock.

On this Martian day, Sol 18, Earth rose over the Sagan Memorial Station at 8:47 p.m. PDT, July 21. Sunrise was at 11:54 p.m. July 21 and Earth set occurred yesterday morning (July 22) at 10:25 a.m. PDT.

"This told us that the spacecraft was basically healthy but that there was a problem with the telecommunications link," said Project Manager Brian Muirhead. A later attempt to communicate with the lander through its high-gain antenna from 7:03 to 7:27 a.m. PDT was not successful.

"The flight team is assessing the possible causes of the communication problem, said Muirhead. "This morning's problem may be related to some extent to configuration problems between the spacecraft and the Deep Space Network, but more data is needed to fully assess the problem. We are trying to troubleshoot a problem with very little information," he said.

The flight team is preparing sequences for a low-gain antenna communications session for about midnight tonight (July 20, Pacific Time). A communications session with the high-gain antenna is planned for about 3:30 a.m. PDT tomorrow, July 21.

"Since we have only limited windows to communicate with the spacecraft we must wait patiently for our next opportunity, Muirhead said. "We will go through the usual steps that have worked for us before, and then we will get to the bottom of the problem as we have before." The telecommunications problem is not thought to be related to the reset problem previously experienced by the lander's computer.

The rover remains safely at the rock called Scooby Doo. Earth will rise over the Sagan Memorial Station at 8:07 p.m. PDT today July 20, and sunrise will be at 11:15 p.m. Earth set is at 9:45 a.m. July 21.

Mars Pathfinder Mission Report
JPL - July 16, 1997 - The Sojourner rover moved away from the rock nicknamed Yogi and headed toward a rock dubbed Scooby Doo during Mars Pathfinder's 12th Martian day, or Sol 12, which just concluded.

The rover moved a total of 3.6 meters (about 12 feet), and has about 2 to 3 meters (7 to 10 feet) to go to reach Scooby Doo. On the way between the two rocks, the rover's alpha proton X-ray spectrometer (APXS) instrument will be taking readings of Martian soil. The science team expects for the APXS instrument to take readings of Scooby Doo on Sol 14 -- equivalent to Thursday night and Friday morning, July 17-18.

Also during the past Martian day, the lander's Imager for Mars Pathfinder (IMP) instrument captured pictures of a Martian sunrise, atmospheric opacity and the lander's windsocks. The imager is also expected to take pictures shortly of a sunset and Mars' moon Phobos.

During Sol 12, Pathfinder's lander sent a total of 65 megabits of data to Earth. All systems are functioning normally. On this Martian day, Earth rise was at 4:47 p.m. Pacific Daylight Time on Tuesday, July 15; sunrise was at 7:56 p.m. PDT; Earth set was at 6:26 a.m. PDT Wednesday, July 16; and sunset was at 8:54 a.m.

While the rover continued its science gathering tasks, the Imager for Mars Pathfinder (IMP) camera continued to take its own spectrographic studies of the Martian terrain. Thursday the camera was used to create the first stereo 3-D pan of the landing site. This "virtual reality" recreation of the rocks, boulders, and landscape, incorporating photo images of the rover and lander as well, will give rover drivers greater confidence in planning safe traverses for the wheeled craft. Thus far, the IMP and rover have taken some 2,280 pictures of Mars as of 1:30pm PDT Thursday.

JPL scientists are also planning to put the IMP to work taking images to help determine the water content of the Martian atmosphere. Friday will see the IMP continue in its detailed photography of the landing site, the so-called "Presidential Pan" due to its high resolution content.

Meanwhile the Sagan Weather Station reported Thursday a virtual heat wave had struck the Ares Vallis. A high of 8 degrees F was recorded by the spacecraft's instruments, with the by now normal low of -100 F. Winds were still out of the west, with a chance of early morning fog Friday hanging around until mid-morning. Friday's targets for spectrographic study were the rocks dubbed Stack, Flattop, Shaggy Dog as well as Yogi.

Following its analysis of the face of "Barnacle Bill", Sojourner put the APXS back on surface soils Tuesday to gather more data on the chemical composition of the top soil layers. During the Martian night Monday evening, the IMP camera was aimed at the heavens, and took the first image of the Martian moon Deimos ever taken from the surface. Spectrographic views of astronomical objects will help scientists determine the composition of the atmosphere of Mars, and how its temperature shifts during the cold evening hours.

In a Martian weather report, scientists said Tuesday that as of 2:45pm local time at the Ares Vallis site, temperature was five degrees above zero F, with a pressure of 6.75 millibars, a pressure about 150 times lower than Earth. Tonight when the sun sets, expect a low of -106 degrees F, with a high Wednesday near zero. Winds at the landing site are currently coming from the northwest, and a light morning fog is possible Wednesday, which will clear rapidly. Wednesday scientists will aim the IMP to the sky in search of cloud formations, more clues to the composition of the red planet -which, by the way scientists say, is several different shades of red and pink. Why? It's Sojourner's job to find out.

The era of microspacecraft exploring the planets has only just started, and others are scheduled to take up the robotic quest begun July 4th on Mars. Out in the dark cold between worlds, the NASA/Lockheed Martin Mars Global Surveyor spacecraft is speeding towards its own rendezvous with the red planet this fall. On September 11, 1997 at 9PM EDT, the remote sensing spacecraft will enter orbit around Mars and begin a year-long research mission. Once in orbit, the spacecraft's sensors and mapping cameras will radio back to Earth new details about Mar's surface, atmosphere, and magnetic fields. Surveyor will make a complete orbit around Mars every two hours. Each orbital "pass" will take the probe over a different part of the Martian terrain. As the weeks and months of observations create new detailed databases for earthbound scientists, a complete global portrait of Mars will emerge. And from time to time, Surveyor will orbit directly overhead its Mars companion and precursor -the now silent Sagan Memorial Station with its stilled rover, Sojourner.

At nearly the same time the Surveyor is reaching Mars, the U.S. plans to return to the Moon with its own version of the Surveyor, a Lunar Prospector. A microspacecraft, the Prospector will orbit the Moon for the first time since the 1960's and seek to confirm whether there is water ice at the lunar South Pole.

More Mars microships will embark from the shores of Earth in 1998, sending more advanced rovers and landers. The 1998 landers will bring new soil microprobes to seek answers about possible formations of water deep beneath the surface.

In 2001, a new orbiter will enter Martian orbit, seeking to identify surface features detected by its predecessor in 1998. That same year, a new rover will collect the first samples from the surface in a base camp that another rover will return to in 2003. That year, an advanced orbiter/lander combination will return to Mars, pick up the samples compiled in 2001, and blast-off from Mars for return to Earth, an historic first in space exploration. These missions of the new century will be conducted in concert with the Russian Space Agency, if the political and economic climate there allows. During this same period, a French and Russian balloon probe will explore Mars. A recent agreement has seen a NASA experiment package added to the craft's payload. Japan, too plans to take up lunar exploration with small robotic craft.

And what beyond 2003? Building on the "faster, better, cheaper" concept, NASA is planning Deep Space 1 and 2, a pair of microcraft to intercept comets and asteroids. The Stardust project may see the return to Earth of a sample from these objects in space. The most startling and advanced projects beyond these are possible Interferometers placed in high orbit near Jupiter. Their mission: to seek alien planets in orbit around other stars. Also being discussed is a spacecraft called Planetfinder, to make detailed deep space observations of the planets found by the Interferometers.

And what then? By the second decade of the 21st century, Mars and the Moon will be fully mapped, and more knowledge about their surfaces will reside in Earth computers than ever before. The International Space Station will have compiled details on how to live and work in space for months and years at a time. Perhaps then, the time will once again be at hand to send humans beyond Earth orbit again, back to the Moon- and onward to Mars.

Historians often refer to the period of space history from 1958 to 1972 as the "Golden Age" of space flight. Perhaps they have been premature. It is just possible that such an age has just begun -started anew on a distant shore of a dusty red planet, by a tiny robot sent by Americans on July 4, 1997: the day the future of spaceflight began anew. ...
...And Space Bank and SpaceCast will bring that to you, too.

For 10 hours in the Martian dark Sojourner has been gathering chemical composition data on the rock's mineralogy. It marks the first time that the rover has used the instrument -its primary scientific tool -on a rock at the landing site. Earlier in the day JPL commanded the IMP camera boom to extend to its full height over the lander and the surface. From that higher perspective the imager took what space officials refer to as the "monster pan" -a panorama of the entire Martian horizon. From the full near six foot height, rocks that loomed as huge Saturday now don't look as imposing, although they still are deemed of great interest as rover visit targets. The camera on the rover also imaged "Bill", as well as looked back at the lander itself, nearly encased in deflated airbags as seen from its height a few inches above the surface.

By midday Monday NASA was plotting pathways for the Sojourner's trek across the Martian surface. And several other rock target priorities were identified for visits in the next few days.

Throughout its first night on the Martian surface, the rover has been gathering scientific composition data by the first use of its primary instrument, the Alpha Proton X-ray Spectrometer. This device, along with filters on the camera aboard the lander and the rover's own cameras, will take the first measurements of the basic make-up of the rocks and soil near the touchdown site and help scientists on Earth determine its mineral content. The spaceship's landing site was deliberately chosen for the scientific value of its surface materials- the Ares Vallis.

Named by the Greeks for the God of passion and war, Ares was named for a valley on Mars that is a great rocky plain believed to have been once flooded with water. The landing site is at the mouth of an ancient outflow channel carved by that flood, an area believed rich in varied types of both rocks and soil. Within minutes of photographing the surface from the lander's camera, scientists selected a gnarled rock, dubbed "Barnacle Bill" that has accumulated Martian dust on one side, and partly uncovered material, perhaps original Martian basaltic material, on the other. The rock is one of Sojourner's prime candidates for a "sample" by its spectrometer once it moves further away from the lander, expected later in its traverses. But the craft will most likely stay within a few tens of meters near the site, the maximum travel distance planned.

Engineers on Earth at JPL, lead by chief rover Brian Cooper, will help navigate the rover during its operation. But given the time it takes for communication between Earth and Mars, about 10 minutes each way, Cooper and his team will only be able to choose targets for the wheeled craft, not truly steer it. An on-board computer will, in fact, do that (space officials gave Cooper a 'Driver's License for Sojourner, signed by U.S. Vice President Al Gore, making Cooper the only rover driver on Earth). With three cameras and a laser system to avoid obstacles in its path, Sojourner will move about on the surface slowly. Its carriage features a "rocker-bogie" wheeled suspension. This means that Sojourner will use rotating joints for its wheels that avoid the necessity for springs, enabling it to conform to the shape of the terrain it travels. It can tilt as much as 45 degrees over a rock without falling over. Motion sensors in its chassis will help the craft avoid such larger rocks.

The rover was designed for a surface exploration "life" of about seven Martian SOLs, a new term coined to describe a Martain day of 24.6 Earth hours. The expectation, however, is that like its Viking precursors, it will last for many times longer. The lander is capable of operating for about 30 SOLs, although it, too, is expected to last much longer. As of late Sunday, all was well with both craft. But the lander was no longer named Pathfinder. It was renamed by the staff of JPL as the "Carl Sagan Memorial Station" - in honor of a man whose vision and determination for scientific truth provided a path that all could find.

Within minutes of examination of the early photography of the rover's activities, indications were received that the craft actually rode over a small rock on its way onto the surface.

The Mars Pathfinder rover is the first ever robotic spacecraft to conduct a mobile exploration of the surface of another world. It was contained aboard the Pathfinder's landing craft during Friday's descent and landing on the surface of Mars at the Ares Vallis, a dry river bed that had been selected by scientists as the target for the Pathfinder mission.

Rocky Gets to Work
Washington DC - July 6, 2:15AM EDT - The Sojourner Mars Pathfinder rover isn't wasting any time in beginning its planned explorations of the surface of Mars. Within minutes of its descent onto the surface Sunday morning the tiny craft extended its main instrument probe and promptly began a 10-hour session analyzing Mars' soil composition.

The craft extended its Alpha Proton X-ray Spectrometer, mounted on the rover's rear, onto the dusty Martian surface. For 10 hours, as the Earth sleeps, the rover will use battery power to continue its testing, cloaked in nighttime darkness with the sun -and the Earth -on the opposite side of Mars.

The rover was to come to a halt shortly after moving away from the ramp, and was to immediately begin a chemical analysis of the surface soils by extending the craft's Alpha Proton X-Ray Spectrometer. The rover is the first robotic, mobile spacecraft to ever roam Mars, and the first U.S. roving craft since the final Apollo lunar landing of December, 1972. The rover's departure onto the surface of Mars was delayed nearly a day by a communications problem that plagued the modems aboard both the landing craft and the rover. From recycling commands sent just before Earthset early Saturday, the problem was cleared, although engineers didn't know this until the Earth rose again over the Pathfinder's landing site at around 4PM EDT Saturday.

In other developments, NASA believes earlier problems with the comms links between the lander and rover have been resolved following frantic reprogramming that now appears to have cleared the problem.

With the communications problem now resolved, a decision to deploy the recover could come at 10:40PM EDT USA tonight. First pictures of Sojourner on its way could then come to Earth around 12:38AM Sunday morning. But officials warned that these timelines were preliminary, and much work remained before the craft could be cleared for its exploration of Mars.

NASA officials reported early Friday that the 9600 baud modems linking communications between the two tiny vehicles were not "talking" with each other. If this problem is not fixed, the rover could still be deployed, using stored commands within its own computer software. But NASA wants the lander to command the rover's planetary adventures. So that will be the focus of day 2's early activities. The sun won't rise over the Ares Vallis until about 1PM EDT USA,, so space officials must wait for the sun's solar energy to power the pathfinder base camp and begin exchanging data with the spacecraft on the surface.

Late Friday, commands were sent to the Pathfinder lander to unfurl the front section of the ramp which Sojourner will use to come rolling down onto the surface. But it was not clear if the commands had been executed by the vehicle before the setting Earth cut off communications. Earlier Friday the lander petal holding the rover was raised 45 degrees, and the airbags beneath were retracted in six cycles. This was done to clear the fabric of the deflated bags from blocking the rover's path once it is commanded down onto the surface. Subsequent photos taken by the lander's base camera seemed to indicate that the bags had been cleared away. Later on Saturday, after a final panorama of the surface, the boom holding that camera will be raised to its full height. All later pictures of Mars taken by that camera will show the surface as would be seen by a standing adult.

This first day on the red planet, one of a possible 30, was a day of triumph for the U.S. space agency. The Mars Pathfinder vehicle reached Mars, entered its atmosphere, deployed its parachute, and then in a never-before-tried maneuver, deployed a cocoon of inflated airbags to cushion its drop to the surface. Both the lander and the rover survived to conduct the first ever mobile exploration of Mars. For NASA, it was a demonstration that the new, micro-sized space vehicles were capable of performing their missions. It opened the promise of sending, in pairs, fleets of the tiny craft to Mars and other worlds, reinvigorating the once broke U.S. planetary exploration program.

Will this "faster, better, cheaper" means of exploring space prove to be the wave of the future? Or just one way of doing science on the cheap - with limited results? Stay tuned - SOL #2 is about to begin. And, after all, it is called Pathfinder, isn't it?

Deployment of the front ramp at the end of this first solar day means that engineers will not have the chance to receive photos of the ramp deployment until tomorrow. This "deployment in the blind" is a sequence that has been practiced by NASA well in advance of the space mission's launch. However, with Earth now setting at the landing site, it is not clear if the commands to do the ramp deployment, as well as a command to stand up the rover and the Alpha Proton X-Ray Spectrometer will be received by the tiny spacecraft.

Washington - July 4, 5:27PM EDT - The Mars Pathfinder lander called Earth today some four and a half hours after touchdown and reported on both its health and the events during its descent through the atmosphere. The spaceship was also to give the latest weather on the red planet. "We have RF signal!", Flight Director Jennifer Harris told her flight control team just after 5:20PM EDT as the first groups of actual digital data was being displayed on Mission Control screens at the Jet Propulsion Lab in California. Engineers are now trying to determine what the data says about the tiny craft's landing events earlier today, the composition of the Mars atmosphere from readings it took during its brief ride down, and the tilt angle of the landing craft relative to the surface area where it landed. Shortly after 5:12PM the lander was to send the first communications, via a 9600 baud modem, to the rover, perched atop one of the craft's landing petals, to determine how it withstood the ride down.

Space officials will now power up and deploy on a boom the camera atop the center main complex on the center petal, and will await the first black and white low quality image from the spacecraft, now expected at around 7:30PM EDT tonight. Thus far, NASA engineers say there have been no alarms received within the data stream, meaning that no out-of-tolerance condition has been experienced by the Mars craft.

If Pathfinder, as has been indicated by early data, landed on its base petal, then the process of retracting the bags and preparing the craft for petal opening will be greatly simplified. About three full hours have been allotted by mission planners for the retraction of the bags and the deployment of the petals. New digital data will not be received from Pathfinder until around 5:07PM EDT today, when the spacecraft will acquire the newly risen Earth and report back on both its health and the weather at the landing site.