Sojourner was the Mars Pathfinder robotic Mars rover that landed on July 4, 1997 and explored Mars for around three months. It has front and rear cameras and several science experiments. Designed for a mission lasting 7 sols, with possible extension to 30 sols, it in fact was active for 83 sols. The base station had its last communication with Earth at 3:23 a.m. Pacific Daylight Time on September 27, 1997. The rover needed the base station to talk to Earth, despite still functioning at the time communications ended.
It has solar panels and a non-rechargeable battery, which allowed limited nocturnal operations. Once the batteries were depleted, it could only operate during the day. The batteries are lithium-thionyl chloride (LiSOCL2) and could provide 150 watt-hours. Additionally, 0.22 square meters of solar cells could produce a maximum of 15 watts, depending on conditions.
Its CPU is a 80C85 with a 2 MHz clock, addressing 64 Kbytes of memory. It has four memory stores; the previously mentioned 64 Kbytes of RAM (made by IBM) for the main processor, 16 Kbytes of radiation-hardened PROM (made by Harris), 176 Kbytes of non-volatile storage (made by SEEQ), and 512 Kbytes of temporary data storage (made by Micron). The electronics were housed inside the Warm Electronics Box inside the rover.
It communicated with the base station with 9600 baud radio modems. The practical rate was more like 2600 baud with a theoretical range of about half a kilometer. The rover could travel out of range of the lander, but its software would need to be changed to that mode. Under normal driving it would periodically send a "heartbeat" message to the lander.
The Alpha Proton X-ray Spectrometer (APXS) is nearly identical to the one on Mars 96, and was a collaboration between the Max Planck Institute for Solar System Research in Lindau, Germany (formally known as the Max Planck Institute For Aeronomy) and the University of Chicago in the United States. APXS could determine elemental composition of Mars rocks and dust, except for hydrogen. It works by exposing a sample to alpha particles, then measuring the energies of emitted protons, X-rays, and backscattered alpha particles.
Sojourner operation was supported by Rover Control Software, which ran on a Silicon Graphics Onyx2 computer back on Earth, and allowed command sequences to be generated using a graphical interface. The rover driver would wear 3D goggles supplied with imagery from the base station, and move a virtual model with the spaceball controller, a specialized joystick. The control software allowed the rover and surrounding terrain to be viewed from any angle or position, supporting the study of terrain features, placing waypoints, or doing virtual flyovers.
- Media related to Mars Pathfinder (rover) at Wikimedia Commons
- Directory of Pathfinder Images
- Edible Spacecraft
Image map of Mars
The following imagemap of the planet Mars has embedded links to geographical features in addition to the noted Rover and Lander locations. Click on the features and you will be taken to the corresponding article pages. North is at the top. Colors represent elevations, from violet (lowest) through blue, green, yellow, orange, red, brown to white (highest).