Spacecraft
At launch the Mars Pathfinder spacecraft will weigh about 890 kilograms (1,962 pounds), including its cruise stage, aeroshell and backshell, solar panels, propulsion stage, medium- and- high-gain antennas and 100 kilograms (220 pounds) of cruise propellant. The cruise stage measures 2.65 meters (8.5 feet) in diameter and stands 1.5 meters (5 feet) tall. The lander resembles a tetrahedron, a small pyramid standing about 0.9 meter (3 feet) tall with three triangular-shaped sides and a base.
When Pathfinder is poised to enter the Martian atmosphere, its main components will be the aeroshell, folded lander and rover, parachute, airbag system and small rocket engines. Combined, the spacecraft will weigh approximately 570 kilograms (1,256 pounds) at entry.
Once it has landed and its airbags have been deflated, Pathfinder will then weigh about 360 kilograms (793 pounds). Subsystems contributing to its landed weight include the open-ing/ uprighting mechanism, lander cabling and electronics, instruments and rover. When it is unfolded and lying flat on the surface, the spacecraft will measure 2.75 meters (9 feet) across and sport a mast-mounted camera poking up about 1.5 meters (5 feet) from the ground.
The lander is controlled by a commercially available control computer, the IBM RAD 6000, which is a radiation-hardened, single-board computer related to the PowerPC. The computer has a 32-bit architecture which executes more than 22 million instructions per second. The computer will store flight software as well as engineering and science data, including images and rover information, in 128 megabytes of available memory.
During interplanetary cruise, the spacecraft requires 178 watts of electrical power, provided by 2.5 square meters (27 square feet) of gallium arsenide solar cells. On the Martian surface, more solar cells will be exposed to the Sun than during cruise and, with batteries, will provide 850 watt-hours on clear days and half that amount of power on days when the Sun is obscured by dust.
The lander has three solar panels, each with an area of 3.3 square meters (35.5 square feet) and supplying 100 watt-hours of power per day. At night, the lander will operate on rechargeable silver zinc batteries with 40 amp hours.
The Pathfinder lander carries a camera on a mast to survey its immediate surroundings. The camera has two optical paths for stereo imaging, each with a filter wheel giving 12 spectral bands in the 0.35 to 1.1 micron range. Its field-of-view is 14 degrees in both horizontal and vertical directions, and it will be able to take one frame (256 by 256 pixels) every two seconds.
