Spirit Rover - Design and Construction

Design and Construction

Main article: Mars Exploration Rover See also: Comparison of embedded computer systems on board the Mars rovers

Spirit (and its twin, Opportunity) are six-wheeled, solar-powered robots standing 1.5 m (4.9 ft) high, 2.3 m (7.5 ft) wide and 1.6 m (5.2 ft) long and weighing 180 kg (400 lb). Six wheels on a rocker-bogie system enable mobility over rough terrain. Each wheel has its own motor. The vehicle is steered at front and rear and is designed to operate safely at tilts of up to 30 degrees. Maximum speed is 50 mm/s (2 in/s); 0.18 km/h, although average speed is about 10 mm/s (0.4 in/s). Both Spirit and Opportunity have pieces of the fallen World Trade Center's metal on them which were "turned into shields to protect cables on the drilling mechanisms".

Solar arrays generate about 140 watts for up to four hours per Martian day (sol) while rechargeable lithium ion batteries store energy for use at night. Spirit's onboard computer uses a 20 MHz RAD6000 CPU with 128 MB of DRAM, 3 MB of EEPROM, and 256 MB of flash memory. The rover's operating temperature ranges from −40 °C to +40 °C (−40 °F to 104 °F) and radioisotope heater units provide a base level of heating, assisted by electrical heaters when necessary. A gold film and a layer of silica aerogel provide insulation.

Communications depends on an omnidirectional low-gain antenna communicating at a low data rate and a steerable high-gain antenna, both in direct contact with Earth. A low gain antenna is also used to relay data to spacecraft orbiting Mars.

Fixed science instruments include

• Panoramic Camera (Pancam) – examines the texture, color, mineralogy, and structure of the local terrain.
• Navigation Camera (Navcam) – monochrome with a higher field of view but lower resolution, for navigation and driving.
• Miniature Thermal Emission Spectrometer (Mini-TES) – identifies promising rocks and soils for closer examination, and determines the processes that formed them.

The rover arm holds the following instruments

• Mössbauer spectrometer (MB) MIMOS II – used for close-up investigations of the mineralogy of iron-bearing rocks and soils.
• Alpha particle X-ray spectrometer (APXS) – close-up analysis of the abundances of elements that make up rocks and soils.
• Magnets – for collecting magnetic dust particles.
• Microscopic Imager (MI) – obtains close-up, high-resolution images of rocks and soils.
• Rock Abrasion Tool (RAT) – exposes fresh material for examination by instruments on board.

The cameras produce 1024-pixel by 1024-pixel images, the data is compressed, stored, and transmitted later.