Spacecraft The entire spacecraft weighs 3,893 kg (8,580 lb) at launch, consisting of 899 kg (1,980 lb) rover; 2,401 kg (5,290 lb) entry, descent and landing system (aeroshell plus descent stage + 390 kg (860 lb) of landing propellant); and 539 kg (1,190 lb) fueled cruise stage.[39]
The Curiosity rover will have a mass of only 900 kg (2,000 lb) including 80 kg (180 lb) of scientific instruments, by the time it lands on the surface of Mars.[19]
Dimensions: The rover is 3 m (9.8 ft) in length, much larger than the Mars Exploration Rovers, which have a length of 1.5 m (4.9 ft) and a mass of 174 kg (380 lb) including 6.8 kg (15 lb) of scientific instruments.[19][40][41]
Speed: Once on the surface, Curiosity will be able to roll over obstacles approaching 75 cm (30 in) in height. Maximum terrain-traverse speed is estimated to be 90 m (300 ft) per hour by automatic navigation; average traverse speeds will likely be about 30 m (98 ft) per hour, based on variables including power levels, terrain difficulty, slippage, and visibility. MSL is expected to traverse a minimum of 19 km (12 mi) in its two-year mission.[42]
Power source: Curiosity is powered by
dilithium crystals a radioisotope thermoelectric generator (RTG), like the successful Viking 1 and Viking 2 Mars landers in 1976.[43][44]
Radioisotope power systems (RPSs) are generators that produce electricity from the natural decay of plutonium-238, which is a non-fissile isotope of plutonium. Heat given off by the natural decay of this isotope is converted into electricity, providing constant power during all seasons and through the day and night, and waste heat can be used via pipes to warm systems, freeing electrical power for the operation of the vehicle and instruments.[43][44] Curiosity's RTG is fueled by 4.8 kg (11 lb) of plutonium-238 dioxide supplied by the U.S. Department of Energy,[45] packed in 32 pellets each about the size of a marshmallow.[19]
Curiosity's power generator is the latest RTG generation built by Boeing, called the "Multi-Mission Radioisotope Thermoelectric Generator" or MMRTG.[46] Based on classical RTG technology, it represents a more flexible and compact development step,[46] and is designed to produce 125 watts of electrical power from about 2000 watts of thermal power at the start of the mission.[43][44] The MMRTG produces less power over time as its plutonium fuel decays: at its minimum lifetime of 14 years, electrical power output is down to 100 watts.[47][48] The MSL will generate 2.5 kilowatt hours per day, much more than the Mars Exploration Rovers, which can generate about 0.6 kilowatt hours per day.
Heat rejection system: The temperatures in the potential areas at which Curiosity may land can vary from +30 to −127 °C (+86 °F to −197 °F). Therefore, the heat rejection system (HRS) uses fluid pumped through 60 m (200 ft) of tubing in the MSL body so that sensitive components are kept at optimal temperatures.[49] Other methods of heating the internal components include using radiated heat generated from the components in the craft itself, as well as excess heat from the MMRTG unit. The HRS also has the ability to cool components if necessary.[49]
Computers: The two identical on-board rover computers, called "Rover Compute Element" (RCE), contain radiation-hardened memory to tolerate the extreme radiation from space and to safeguard against power-off cycles. Each computer's memory includes 256 KB of EEPROM, 256 MB of DRAM, and 2 GB of flash memory.[50] This compares to 3 MB of EEPROM, 128 MB of DRAM, and 256 MB of flash memory used in the Mars Exploration Rovers.[51]
The RCE computers use the RAD750 CPU, which is a successor to the RAD6000 CPU used in the Mars Exploration Rovers.[52][53] The RAD750 CPU is capable of up to 400 MIPS, while the RAD6000 CPU is capable of up to 35 MIPS.[54][55] Of the two on-board computers, one is configured as backup, and will take over in the event of problems with the main computer.[50]
The rover has an Inertial Measurement Unit (IMU) that provides 3-axis information on its position, which is used in rover navigation.[50] The rover's computers are constantly self-monitoring to keep the rover operational, such as by regulating the rover's temperature.[50] Activities such as taking pictures, driving, and operating the instruments are performed in a command sequence that is sent from the flight team to the rover.[50]
Communications: Curiosity has two means of communication – an X band transmitter and receiver that can communicate directly with Earth, and a UHF Electra-Lite software-defined radio for communicating with Mars orbiters. Communication with orbiters is expected to be the main path for data return to Earth, since the orbiters have both more power and larger antennas than the lander.[56]
At landing, telemetry will be monitored by the Mars Odyssey satellite, Mars Reconnaissance Orbiter and ESA's Mars Express. Odyssey is capable of relaying UHF telemetry back to Earth in real time, which will take 13:46 minutes.[57] [58]
Mobility systems: Like previous rovers Mars Exploration Rovers and Mars Pathfinder, Curiosity is equipped with 6 wheels in a rocker-bogie suspension. The suspension system will also serve as landing gear for the vehicle, unlike its smaller predecessors.[59] Curiosity's wheels are significantly larger than those used on previous rovers. Each wheel has a pattern that helps it maintain traction but also leaves patterned tracks in the sandy surface of Mars. That pattern is used by on-board cameras to judge the distance traveled. The pattern itself is Morse code for "JPL" (·--- ·--· ·-··).[60]
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