NASA Facts National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, CA 91109 Mars Pathfinder Mars Pathfinder was the first completed mission events, ending in a touchdown which left all systems in NASAs Discovery Program of low-cost, rapidly intact. developed planetary missions with highly focused sci- The landing site, an ancient flood plain in Mars ence goals. With a development time of only three northern hemisphere known as Ares Vallis, is among years and a total cost of $265 million, Pathfinder was the rockiest parts of Mars. It was chosen because sci- originally designed entists believed it to as a technology be a relatively safe demonstration of a surface to land on way to deliver an and one which con- instrumented lander tained a wide vari- and a free-ranging ety of rocks robotic rover to the deposited during a surface of the red catastrophic flood. planet. Pathfinder In the event early in not only accom- Mars history, sci- plished this goal but entists believe that also returned an the flood plain was unprecedented cut by a volume of amount of data and water the size of outlived its primary North Americas design life. Great Lakes in Pathfinder used about two weeks. an innovative The lander, for- method of directly mally named the entering the Carl Sagan Martian atmos- Memorial Station phere, assisted by a following its suc- parachute to slow cessful touchdown, its descent through and the rover, the thin Martian atmosphere and a giant system of named Sojourner after American civil rights crusader airbags to cushion the impact. It was the first time Sojourner Truth, both outlived their design lives this airbag technique had been used. After the entry the lander by nearly three times, and the rover by 12 vehicle entered Mars atmosphere from its interplane- times. tary trajectory, it successfully completed a 4-1/2- From the landing on July 4, 1997, to the final data minute sequence of complex and precisely timed transmission on September 27, 1997, Mars Pathfinder Wind Sensor Thermocouples Wind Socks Atmospheric Structure Instrument Solar Panel and Meteorology Package (ASI/MET) Low-Gain Imager for Mars Antenna Pathfinder (IMP) ASI/MET Accelerometers High-Gain Antenna Rover Solar Panel Solar Panel Instrument Electronics Assemblies Alpha Proton X-ray Spectrometer returned 2.3 billion bits of information, including included a Star 48 solid rocket as the third-stage more than 16,500 images from the lander and 550 booster. images from the rover, as well as more than 15 chem- During the spacecrafts seven-month journey to ical analyses of rocks and soil and extensive data on Mars, four trajectory correction maneuvers fine-tuned winds and other weather factors. Findings from the its flight path. NASAs Deep Space Network of giant investigations carried out by scientific instruments on dish antennas provided the two-way communications both the lander and the rover suggest that Mars was at link for command, tracking and telemetry operations. one time in its past warm and wet, with water existing Except for some difficulty with two of the space- in its liquid state and a thicker atmosphere. crafts five Sun sensors early in the flight, all critical Overall, the Pathfinder mission was a great suc- spacecraft subsystems performed as expected. cess, providing scientists with large amounts of data, At 1:42 p.m. PDT on June 30, 1997, the flight pioneering many new technologies, and demonstrat- team commanded the spacecraft to switch into its ing the feasibility of developing, designing launching mode for entry, descent and landing on Mars. On July and operating a planetary mission according to 3, 1997, at about 4 a.m. PDT, the spacecraft passed NASAs new faster, better, cheaper philosophy. into the sphere of Mars gravitational influence. Early Mission Overview on July 4, 1997, Pathfinder was heading for its Mars Pathfinder was launched atop a Delta II- approximately 100- by 200-kilometer (60- by 120- 7925 launch vehicle from Cape Canaveral Air Station mile) landing ellipse. in Florida on December 4, 1996. The launch vehicle The sequence of entry, descent and landing events was as follows: release of the cruise stage (34 minutes 2 prior to landing), entry into Mars upper atmosphere sent confirmation back to Earth that Pathfinder had (4 minutes to landing), deployment of the 11-meter- landed. Approximately 90 minutes after landing, engi- diameter (36-foot) parachute (2 minutes to landing), neering data received by the flight team indicated that release of the heat shield, release of the lander from Pathfinder had fully deployed its petals and was the backshell and descent of the lander on a 20-meter awaiting sunrise on Mars to begin its mission. The (65 foot) tether, acquisition of altitude information by lander came to rest about 20 kilometers (12 miles) the radar altimeter, inflation of the airbags (8 seconds southwest of its targeted landing spot and was resting to landing), firing of the rocket-assisted deceleration on the surface at a very slight tilt of about 2.5 engines, cutting of the tether, and free-fall of the lan- degrees. der to the Martian surface. Pathfinders first transmission via the landers The airbag-cushioned lander hit Martian soil at low-gain antenna was received on time at 2:07 p.m. 10:07 a.m. PDT on July 4, 1997, at a speed of 14 PDT on July 4, 1997, or sol 1 (a Martian day, or meters per second (31 miles per hour). Measuring 5.8 sol, is 24 hours, 37 minutes). The transmission con- meters (19 feet) in diameter, it bounced like a giant tained preliminary information about the health of the beach ball about 15 times, as high as 15 meters (50 spacecraft and rover; the spacecrafts orientation on feet), before coming to rest 2-1/2 minutes later about the surface; data about its entry, descent and landing; 1 kilometer (six-tenths of a mile) from the point of and a first look at the density and temperatures of the initial impact. The landing coordinates were 19.13 Martian atmosphere. degrees north latitude, 33.22 degrees west longitude, Pathfinders first transmission via its high-gain in the boulder-strewn Ares Vallis flood plain. antenna, beginning at 4:28 p.m. PDT the same day, Fortuitously, the lander came to rest right side up on returned to Earth the first images taken by the lan- its base petal, thereby eliminating the need for the ders camera, including a color mosaic of the boulder- spacecraft to right itself while deploying its petals. strewn Ares Vallis flood plain. Some of the images An antenna mounted on one of the landers petals revealed that one of the airbags had not fully retract- Antenna Solar Panel Material Alpha Proton Adherence X-ray Spectrometer Experiment Cameras/ Lasers Rocker-Bogie Warm Electronics Box Mobility System 3 ed, and was obstructing opening of one of the rover ed to reestablish contact with the spacecraft for sever- ramps. al months until March 1998, but were unable to Also on its first day on Mars, Sojourner, which regain contact. Although the cause of the loss of com- was programmed to communicate with the lander as munication with the lander may never be known, frequently as every 10 minutes, was not completing engineers suspected that depletion of the spacecrafts full sentences in its transmissions to the lander. This battery and a drop in the operating temperature of the communication problem which engineers conclud- spacecraft, which was kept warm by the battery, were ed was the result of a problem with the modem on the to blame. (The battery was only designed to operate lander used to communicate with the rover was for one month.) The rover had completed an APXS solved the next day. study of a rock nicknamed Chimp when it was last After receiving hundreds of new images of the heard from. Assuming that the lander was not func- Ares Vallis outflow channel, the flight team spent the tioning after the loss of signal, it is assumed that the rest of sol 1 retracting the airbag obstructing the rover rover would have gone into a contingency mode with- ramp. On the night of July 5, late in the second in a few days -- either circling the lander repeatedly Martian day, or sol 2, Sojourner stood up to its full or standing in place, awaiting instructions. The height of 30 centimeters (1 foot) and rolled down the Pathfinder mission was declared officially concluded landers rear ramp, which was tilted at 20 degrees in March 1998. from the surface, well within the limits of safe The only objective left unfinished at the time deployment. Sojourner then positioned its primary communications was lost was completion of a high- science instrument, an alpha proton X-ray spectrome- resolution 360-degree image of the landing site nick- ter (APXS), face-down in the Martian soil to take 10 named the Super Pan, of which 83 percent was hours of measurements overnight. received on Earth. Other complete panoramas had On sol 3, Sojourner performed two science exper- already been received. iments: a soil mechanics experiment designed to Mars demonstrate how the rovers wheels and mobility sys- One of five planets known to the ancients, Mars is tem operate on the Martian surface; and a trip of known as the red planet because of its reddish color. about 36 centimeters (1.2 feet) to a rock nicknamed At times it is the third brightest planet, after Venus Barnacle Bill, against which Sojourner placed the and Jupiter. Mars was named by the Romans for their APXS overnight to gather data on its composition.