Landing platform and small rover on Mars.

Mars Pathfinder Lander and Sojourner Rover on Mars.

Goals: Mars Pathfinder was designed primarily to demonstrate a low-cost way of delivering a set of science instruments and a free-ranging rover to the surface of the Red Planet. The unique airbag system cushioned the lander in a cocoon after a parachute and rocket descent through the thin Martian atmosphere.

Accomplishments: Mars Pathfinder demonstrated a number of innovative, economical, and highly effective approaches to spacecraft and mission design. The wagon-sized Sojourner rover was the forerunner of more advanced rovers such as Spirit, Opportunity and Curiosity. Both Spirit and Opportunity used a variation of the airbag system to land on Mars. The Carl Sagan Memorial Station also used an innovative petal design that unfolded after landing, exposing its science instruments and releasing the rover to explore surrounding rocks.

In addition to its engineering accomplishments, Pathfinder made significant contributions to what was known about Mars' geology and meteorology at the time.

4 Dec 1996: Launch
4 Jul 1997: Mars Landing
5 Jul 1997 - 25 Sep 1997: Sojourner Rover Operations
27 Sep 1997: End of Mission

Mission Type: Lander, Rover
Launch Vehicle: Delta 7925 (no. D240)
Launch Site: Cape Canaveral Air Station, Fla., USA
NASA Center: Jet Propulsion Laboratory
Spacecraft Mass:
Lander: 895 kg (1,973 pounds) at launch
Sojourner rover: 10.6 kilograms (23 pounds)
Spacecraft Instruments:
1) IMP imaging system (included magnets and wind socks)
2) APXS alpha/proton/x-ray spectrometer
3) ASI/MET atmospheric structure/meteorology package
Sojourner rover:
1) imaging system (three cameras)
2) laser stripers
3) accelerometers
4) potentiometers
Spacecraft Dimensions:
Lander: Tetrahedron, three sides and base, standing 0.9 meter (3 feet) tall
Sojourner rover: 65 cm (2 feet) long by 48 cm (1.5 feet) wide by 30 cm (1 foot) tall
Spacecraft Power: Solar Panels; Batteries
Maximum Power:
Lander: 160 W
Rover: 16 W
Total Cost: $171 million (capped at $150 million in fiscal year 1992 dollars), plus $25 million for rover.
Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, Monographs in Aerospace History No. 24, by Asif A. Siddiqi

National Space Science Data Center,

Mars Pathfinder was an ambitious mission to send a lander and a separate, remote-controlled rover to the surface of Mars, the second of NASA's Discovery missions.

Launched one month after Mars Global Surveyor, Pathfinder was sent on a slightly shorter seven-month trajectory designed for earlier arrival. The main spacecraft included a 10.6-kilogram, six-wheeled rover known as Sojourner capable of traveling 500 meters from the main ship at top speeds of 1 centimeter per second. The mission's primary goal was not only to demonstrate innovative, low-cost technologies, but also to return geological, soil, magnetic property, and atmospheric data.

After a seven-month traverse and four trajectory corrections (on 10 January, 3 February, 6 May, and 25 June 1997), Pathfinder arrived at Mars on 4 July 1997. The spacecraft entered the atmosphere and was then slowed by aerobraking, retrorockets, and a parachute before bouncing on the surface using cushioned landing bags that had deployed 8 seconds before impact.

Pathfinder landed at 16:56:55 UT on 4 July 1997 at 19.30° north latitude and 33.52° west longitude in Ares Vallis, about 19 kilometers southwest of the original target. Impact speed was about 10.5 meters per second; the spacecraft bounced several times before coming to a complete stop.

The next day, Pathfinder deployed the Sojourner rover on the Martian surface via landing ramps. Sojourner was the first wheeled vehicle to be used on any other planet of the solar system.

During its eighty-three-day mission, the rover covered hundreds of square meters, returned 550 photographs, and performed chemical analyses at sixteen different locations near the lander. The latter, meanwhile, transmitted more than 16,500 images and 8.5 million measurements of atmospheric pressure, temperature, and windspeed.

Data from the rover suggested that rocks at the landing site resembled terrestrial volcanic types with high silicon content, specifically a rock type known as andesite.

Although the planned lifetimes of Pathfinder and Sojourner were expected to be one month and one week, respectively, these times were exceeded by three and twelve times, respectively. Final contact with Pathfinder was at 10:23 UT on 27 September 1997. Although mission planners tried to reestablish contact for the next five months, the highly successful mission was officially declared terminated on 10 March 1998. After landing, Mars Pathfinder was renamed the Sagan Memorial Station after the late astronomer Carl Sagan.

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