Prime Mission
Mars Pathfinder’s primary mission will begin when its lander petals have been fully unfolded and the lander switches to a sequence of computer commands that will control its functions. The spacecraft will land about four hours before sunrise on Mars and will spend the time in darkness retracting its airbags, standing itself upright and opening the petals so that solar panels can be powered up with the first light of sunrise.
The lander’s first task will be to transmit engineering and science data collected during its descent through the thin atmosphere of Mars. If no errors are detected in these data, a real-time command will be sent from Earth instructing the lander to unlock the imager camera head, deploy and point the high-gain antenna on its pop-up mast, roll out two rover exit ramps and unlatch the 10-kilogram (22-pound) rover.
Next, the lander’s camera will take a panoramic image of the Martian landscape and begin transmitting the data directly to Earth at a few thousand bits per second. The first images of the Martian landscape, which will be returned to Earth within 35 minutes of the start of the primary mission, will show engineers whether the petal on which the rover sits is flat against the surface or tilted against a rock. The image will also show the terrain beyond both rover exit ramps so that engineers may decide which route looks safer.
Once a decision on the route has been made, commands will be sent to deploy the rover. Sojourner will spend about an hour exiting its ramp.
Driving off onto the floor of an old outflow channel, Sojourner will explore the surface at the command of Earth-based operators, who will rely on lander-based images to select a path and target for the rover. The six-wheeled Sojourner travels at 1 centimeter (0.4 inch) per second, performing mobility tests, imaging its surroundings and deploying an alpha proton x-ray spectrometer designed to study the elemental composition of rocks. Altogether, the rover will range a few tens of meters (yards) from the lander.
Also mounted on the lander are wind sensors, wind socks and high- and low-gain antennas. Instruments will be used to measure pressure, temperature and density of the Martian atmosphere. Magnets mounted on the lander will collect magnetic specimens of Martian dust and soil as small as 100 microns.
Much of the lander’s mission after this will be focused on supporting the rover with imaging, telecommunications and data storage.
