This mission, managed for NASA by Jet Propulsion Laboratory (JPL) is part of the Discovery Program for planetary missions. Pathfinder will be launched aboard a Delta II Rocket. Pathfinder will arrive on Mars July 4, 1997. One of the unique aspects of the missions is that the craft will go directly from Earth to Mars and land instead of going into orbit.
When the craft enters the Martian atmosphere, it will use a parachute along with a rocket breaking system and air bags to ensure a soft, upright landing. The lander will make atmospheric and meteorological observations during descent and once on the surface, it will act as a weather station and a radio relay for the Rover.
During the flight to Mars, the Rover (named Sojourner) is carried in a stowed configuration with the body lowered, because of available space. Once on Mars, it will extend to its full height before it leaves the lander. It will roll down a deployment ramp to the surface and will then be independent except for using the lander data and communications functions for contact with Earth.
The Rover will
be operated for at least 7 sols. If all goes well, and the lander and Rover
are functioning well, the mission may be continued: one year for the lander,
and up to 30 sols for the Rover.
The actual landing site of the Pathfinder is an ancient flood plain on Mars, known as Ares Vallis. The site is 850 km southeast of the first Viking lander. One of the deciding factors for this site was the amount of sunlight it will receive during the mission period. Since the Rover is solar powered, maximum sunlight is a must. During July, the sun is directly over the 15 N latitude site. The site is also of major geologic interest. It is at the mouth of a large outflow channel where there is likely to be a large variety of rock samples. The rocks would have been washed down during a time when floods washed over the surface of Mars.
The operator on Earth views the work station with a stereo display of the lander's image of the terrain through three-dimensional glasses. The work station's software places an icon of the rover in the scene and the coordinates of the placement are determined. Those coordinates form the basis of the rover commands to traverse the surface Vehicle motion control is accomplished through the on/off switching of the drive or steering motors. An average of motor drive or steering readings determines when to switch off the motors. When motors are off, the computer conducts a proximity and hazard detection function, using its laser striping and camera system to determine the presence of obstacles in its path. The vehicle is steered autonomously to avoid obstacles but continues to achieve the commanded goal location
During
the initial mission, the Rover will take at least 3 pictures of the Lander
to ascertain the degree of any damage that may have been sustained. There
will also be an option for close up stereoscopic pictures of any specific
damaged sites.