After a very tense early morning, when communications with the still stowed Sojurner rover were intermittent and unreliable, the second sol on Mars has turned to triumph.

At approximately 5:00 pm Pacific Daylight Time, confirmation that communications were reliably re-established with the rover was received in Mission Control. Two hours later, during the next downlink session, confirmation was received that the rover deployment ramps were deployed on both sides of the petal on which it rested. After careful analysis of the images provided by the IMP camera, rover controllers decided to deploy the rover off the right-hand ramp. Stand up was confirmed during the final downlink session of this historic day, and the IMP again provided dramatic pictures of the rover moving down the selected ramp onto the surface of the Red Planet. Clear tracks were visible in the dusty soil and the rover came to rest about 10 cm from a nearby rock. During the martian night it will deploy its Alpha Proton X-Ray Spectrometer (APXS) onto the surrounding soil for 10 hours, and finally go into "sleep" mode to await the dawn of the next exciting new sol. 

Mars Pathfinder's robust, 23-pound rover named Sojourner successfully rolled off its ramp tonight and onto the Martian surface, becoming the first robotic vehicle ever to explore the surface of another planet.

The first image showing Sojourner with its six wheels firmly planted in sandy Martian terrain was received on Earth at about 10:59 p.m. PDT. The rover team did not know immediately what time the rover actually set foot on Martian soil. Rover deployment occurred within 10 minutes of Earth set, at which time telecommunications on Mars ceases as the Earth disappears below the horizon. Two-way communications resume at about 11 a.m. PDT on Sunday, July 6.

July 5, 1997

"Six wheels on soil!" This image was taken by the IMP camera on July 5, 1997. Sojourner's descent down the rear rover deployment ramp was successful. The microrover's seven month journey from Earth to Mars is complete. The soil beneath Sojourner (with tracks showing behind the right rear wheel) will be the first target of the Alpha Proton X-Ray Spectrometer.

 The operations team examined a set of black-and-white images showing the ramp deployment before activating the command sequence to deploy the rover. More than 90 frames coming down during an 8 - 9:15 p.m. PDT transmission showed that both ramps were situated at angles well within the limits of safe deployment. The rover team sent Sojourner down the rear ramp, or the ramp on the right side of the lander, which was tilted at just 20 degrees from the surface. The rover would not have been able to roll off the ramps had they exceeded a 30-degree tilt.

Sojourner made the trek down its ramp in two stages, first crawling half way down the ramp and stopping to take a photograph of the ramp, then continuing its 4-minute journey off the ramp. Additional images showed rover wheel tracks in soft Martian soil and the rover standing about 10 centimeters (0.3 feet) from the end of the ramp. The lander's camera also took photographs of the rover's exit. Once off the ramp, Sojourner unlatched its primary science instrument, an alpha proton X-ray spectrometer, and positioned it face down in the Martian soil to take 10 hours of measurements overnight.

The first science investigations beginning on Sunday, July 6, the third day of surface operations, are likely to include a soil mechanics experiment to observe how the rover's wheels and mobility system operate on the Martian surface and a rover photography session to create a "monster pan" of the surface in multiple color, high resolution format. The operations team also plans to increase Pathfinder's data rate to 6,300 bits per second to retrieve as much data as possible over the next week, which marks the primary lifetime of the rover.

A press briefing to announce science activities for day three is scheduled for 10 a.m. PDT on Sunday, July 6, in JPL's von Karman Auditorium. 

After receiving hundreds of new images of a boulder-strewn outflow channel known as Ares Vallis, NASA's Mars Pathfinder flight team spent the rest of Sol 1 - the equivalent of one day on Mars - rearranging an airbag that was covering the edge of the rover's petal so that the hearty, 23-pound vehicle can safely roll off its ramp later this afternoon.

The rover team decided last night to conduct further airbag retraction after studying the first set of black-and-white images to be returned via Pathfinder's high-gain antenna. A new software sequence was prepared and tested prior to transmission at 7:08 p.m. PDT. The command instructed the lander to pull the obstructed petal up about 45 degrees, further retract the airbag underneath the petal, then lay the petal down again. Data later in the evening indicated that the maneuver had been successful in clearing the airbag from the edge of the rover's petal.

These images show that the Mars Pathfinder airbags have been successfully retracted, allowing safe deployment of the rover ramps. The airbags visible prominently in the top image are noticeably retracted at the bottom of the second image. The Sojourner rover is at lower right in this second image, and rocks are visible in the background.

 Before Earth set on Mars at about 10:30 p.m. PDT, telecommunications engineers reported that Sojourner, which is programmed to communicate with the lander as frequently as every 10 minutes, was not "completing full sentences" in its transmissions to the lander. Dr. Jacob Matijevic, rover team leader, said at a 10 a.m. PDT press briefing today that the problem is most likely a software synchronization problem between the rover and lander. The team will conduct a brief communications session at 1 p.m. PDT to reset some of the modem parameters on the rover.

Meanwhile, the team was still waiting to learn if a set of commands set last night to deploy the second ramp and unlatch the rover had been carried out. They expected confirmation one way or the other during the next high-gain antenna downlink session at 2:30 p.m. PDT today. Once the ramp has been unfurled, the rover will stand up to its full height of 1-foot tall and roll off the forward ramp. The rover team reported today that the front ramp appears to be the safest exit route with fewer rocks on the surface at the end of the ramp. Sojourner will not be deployed until about 7:40 p.m. and will spend about five minutes driving off its ramp.

Scientists spent several hours last night comparing the landing site to Viking images of the region. Dr. Peter Smith, principal investigator on the lander camera team, said the lander is about 20 miles south of a large mountain peak and within about 3 to 4 kilometers (1.8 to 2.4 miles) northwest of the rim of a crater believed to be at least several miles in diameter. Dr. Matthew Golombek, the Mars Pathfinder project scientist, added that two rocks in the immediate vicinity of the lander, had been singled out as the first targets for the rover's travels, based on their varying colors and shapes, which may suggest different origins and compositions.

Earth rise over Mars - which brings Earth into the proper alignment for communications with the Pathfinder lander and rover - - began at 10:08 a.m. PDT today. The operations team has about 11 hours in which to conduct surface operations during this second day of Mars exploration. A press briefing to update the day's events will be held at 5 p.m. PDT and a final, wrap-up briefing will be held at 9 p.m. PDT. Both will be carried on NASA TV, which is available on GE-2, transponder 9C at 85 degrees west longitude, vertical polarization, with a frequency of 3880 MGz and audio of 6.8 MHz.

The public is encouraged to follow Mars Pathfinder mission activities via the World Wide Web by visiting the Pathfinder site at: http://mpfwww.jpl.nasa.gov.