The basic design of the Mars Pathfinder spacecraft involves an aeroshell, parachute, solid rocket, and an air bag entry, descent and landing system. It has a self-righting tetrahedral lander with heater units. It also carries a free-ranging micro-rover. The Integrated Attitude and Information Management System handles the command and data for the spacecraft.
Utilizing a R6000 computer with VME bus, Pathfinder can execute anywhere from 2.5 to 20 million instructions per second (mips) for computation. The mass memory of this computer can hold 128 million bytes.
Power is received in the cruise stage and lander through gallium arsenide/germanium solar cells. Cruise power is 250-460 watts with 1080 watt hours of daily energy available on the surface.
For surface operations, the telemetry rate via the High Gain Antenna/X-band is 1.2 to 12 kbps for the 70-m Deep Space Network antenna. The command rate via HGA/X-band is 250 b/s.
For propulsion, the spacecraft carries monopropellant hydrazine used for cruise and eight 4.4 newton thrusters.
Launch Mass 870 kg (with propellant) Entry Mass 566 kg Lander Mass 325 kg
The Rover
The rover, whose official name is Micro-rover Flight Experiment, weighs less than 14 kg (31 lbs.) including its mounting and deployment equipment. Its mobile mass is 11.5 kg (25 lbs.) including Alpha Proton X-ray Spectrometer (APXS) deployment mechanism and APXS instrument. The Lander-Mounted Rover Equipment Mass is 4.5 kg (10 lbs.) including an ultra-high-frequency (UHF) modem and support structure.
The amount of work this rover can accomplish is amazing considering that it only is 630 mm (25.4 inches) long by 480 mm (18.7 inches) wide. Two of the factors limiting its volume is the lander's shape and the fact that there are many other necessary systems on board.
Onboard autonomous navigation utilizes laser striping to detect obstacles. A six-wheel, rocker-bogie suspension has been chosen for this vehicle. A UHF link with the lander provides command and telemetry for the rover. Among its payload are aft and fore cameras, APXS, and the APXS deployment mechanism. The rover will be able to get power via 0.25-square-meter solar panels, which produce a peak power of 16 watt hours. Its primary battery provides 150 watt hours. Included are three radioisotope heater units necessary for temperature control. Its computer is a 0.5 kg 80C85 that can execute 0.1 mips with a 0.5 megabyte RAM mass storage. Surface operation is expected to occur from 10 a.m. to 2 p.m. each Martian day.
Rover Operations
The rover will be controlled remotely from Earth. There will be a a workstation with a stereo display, a sort of 3-d display where images of the surrounding terrain taken from the lander will be viewed. An icon of the rover will be placed over this image. This allows the coordinates to control the rover's movement to be easily determined.
Instrument Mass(kg) Power (W) Atmospheric Structure Instrument/Meteorology Experiment (ASI/MET) 2.41 4.2 (landed) Imager for Mars Pathfinder (IMP) 6.22 5.7 APXS 0.56 0.4 (data mode) The chart is taken from the the Mars Global Surveyor Fact Sheet from NASA's Jet Propulsion Laboratory
