Mission overview

Mission overview video
Mission overview audio

At launch complex 17-B, Cape Canaveral, Florida, a Delta II stands ready to lift off, carrying a spacecraft called Mars Pathfinder. Sometime between December 2nd and December 31st, 1996, this launch vehicle, supplied by McDonnell Douglas Corporation, will set NASA's new Mars lander on a course to the red planet.

One minute after launch, the Delta will cast off six of its solid rocket boosters. Shortly after, the remaining three will separate from the first stage. After clearing the lower atmosphere, the rocket shroud will fall away, exposing the spacecraft. Pathfinder will briefly coast in orbit around the Earth before the second and third stages send it onward to Mars.

With its conical heat shield pointing the way, the spacecraft will fire thrusters to adjust its flight path for its seven month journey to Mars. Pathfinder will travel more than 500 million kilometers before its rendezvous with Mars. Five days before its arrival on Mars, the spacecraft will turn to its entry position. The cruise stage will be jettisoned just 30 minutes before the entry vehicle dives directly into the Martian atmosphere.

The atmospheric friction of entry will create a fountain of fireworks around the craft, but Pathfinder will be protected by a Viking-derived heatshield, as it pierces the thin Martian atmosphere at 27,000 kilometers per hour. Descending on the night side of Mars, the spacecraft will deploy a parachute when its speed slows to less than 1,500 kilometers per hour.

The heatshield will be released. Then, the lander will be separated from the backshell on a bridle, 18 meters long. A few seconds before the landing, five meter diameter airbags will inflate to cushion the impact. Retro-rockets will fire to stop the spacecraft and suspend it briefly in mid-air just before landing. Because Mars has only about one-third the gravity of Earth, the spacecraft will bounce as high as a ten-story building before coming to a halt. Four airbags surround the lander. Each is made of six lobes, which will protect the 360 kilogram spacecraft inside.

After the airbags have stopped rolling, they will be deflated and retracted, exposing the lander. Small motor engines will drive open the lander's petals, like a flower, and stand it upright, revealing the rover and the science instruments. As the sun rises, the spacecraft will power up, drawing on the energy from its solar panels to spring to life. The lander's camera will take its first look and locate the directon of the sun. The communications antenna's will be deployed, and two ramps will unfurl to allow for the rover's exit.

The rover, named Sojourner, will rise to its full height and deploy its communications antennas. Next the lander imager and the weather station will deploy to their full heights, and the imager will scan the horizon. Once the first panorama of Mars has been sent back to Earth, Sojourner will power up and venture out onto the surface for a closer look. The rover will use lasers and cameras to detect rocks and other surface objects in its path as it moves about the surface. Its chassis incorporates a rocker-bogie suspension system, very stable and flexible for scaling rocks nearly half its own height. Objects too big to drive over will be circumnavigated.

Sojourner weighs just 11 kilograms, and stands 45 centimeters tall by 60 centimeters long. Its power source is a top-mounted solar panel, with a maximum capacity of 16 watts. Once the rover has found a rock of interest, it will deploy its Alpha Proton X-ray Spectrometer, and place it against the rock. It will take ten hours to determine the composition of the target. Sojourner will then move on to its next candidate rock. As night falls, the rover will fall silent, and await a new day of exploration with the rising sun.

The Pathfinder lander and rover mission is managed by the Jet Propulsion Laboratories for NASA's office of space science.