Pathfinder

Mars Pathfinder (MESUR Pathfinder) is an American robotic spacecraft that landed a base station with a roving probe on Mars in 1997. It consisted of a lander, renamed the Carl Sagan Memorial Station, and a lightweight (10.6 kg/23 lb) wheeled robotic Mars rover named Sojourner, which became the first rover to operate outside the Earth–Moon system.

Launched on December 4, 1996 by NASA aboard a Delta II booster a month after the Mars Global Surveyor was launched, it landed on July 4, 1997 on Mars's Ares Vallis, in a region called Chryse Planitia in the Oxia Palus quadrangle. The lander then opened, exposing the rover which conducted many experiments on the Martian surface. The mission carried a series of scientific instruments to analyse the Martian atmosphere, climate, geology and the composition of its rocks and soil. It was the second project from NASA's Discovery Program, which promotes the use of low-cost spacecraft and frequent launches under the motto "cheaper, faster and better" promoted by the then administrator, Daniel Goldin. The mission was directed by the Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology, responsible for NASA's Mars Exploration Program. The project manager was JPL's Tony Spear. This mission was the first of a series of missions to Mars that included rovers, and was the first successful lander since the two Vikings landed on the red planet in 1976. Although the Soviet Union successfully sent rovers to the Moon as part of the Lunokhod program in the 1970s, its attempts to use rovers in its Mars program failed.

In addition to scientific objectives, the Mars Pathfinder mission was also a "proof-of-concept" for various technologies, such as airbag-mediated touchdown and automated obstacle avoidance, both later exploited by the Mars Exploration Rover mission. The Mars Pathfinder was also remarkable for its extremely low cost relative to other unmanned space missions to Mars. Originally, the mission was conceived as the first of the Mars Environmental Survey (MESUR) program.

Mission objectives

 * To prove that the development of "faster, better and cheaper" spacecraft was possible (with three years for development and a cost under $150 million).
 * To show that it was possible to send a load of scientific instruments to another planet with a simple system and at one fifteenth the cost of a Viking mission. (For comparison, the Viking missions cost $935 million in 1974 or $3.5 billion in 1997 dollars.)
 * To demonstrate NASA's commitment to low-cost planetary exploration by finishing the mission with a total expenditure of $280 million, including the launch vehicle and mission operations.Pathfinder 3.gif

End of mission
Although the mission was planned to last from a week to a month, the rover operated successfully for almost three months. Communication failed after 7 October, with a final data transmission received from Pathfinder at 10:23 UTC on September 27, 1997. Mission managers tried to restore full communications during the following five months, but the mission was terminated on March 10, 1998. During the extended operation a high-resolution stereo panorama of the surrounding terrain was being made, and the Sojourner rover was to visit a distant ridge, but the panorama was only about one-third completed and the ridge visit had not begun when communication failed.

The on-board battery—designed to operate for one month—may have failed after repeated charging and discharging. The battery was used to heat the probe's electronics to slightly above the expected nighttime temperatures on Mars. With the failure of the battery, colder-than-normal temperatures may have caused vital parts to break, leading to loss of communications.

After the landing, Pathfinder was renamed as the Sagan Memorial Station in honour of astronomer and planetologist Carl Sagan. The mission had exceeded its goals in the first month.

Landing Site
The landing site was an ancient flood plain in Mars's northern hemisphere called "Ares Vallis" ("the valley of Ares", the ancient Greek equivalent of the ancient Roman deity Mars) and is among the rockiest parts of Mars. Scientists chose it because they found it to be a relatively safe surface to land on and one that contained a wide variety of rocks deposited during a catastrophic flood. After the landing, at 19.13°N 33.22°WCoordinates: 19.13°N 33.22°W, succeeded, the landing site received the name The Carl Sagan Memorial Station in honour of the astronomer.