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Curiosity (rover)

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This article is about the planetary science robotic surface mission on Mars. For the spaceflight mission, see Mars Science Laboratory.

Template:Infobox spacecraft The Curiosity rover is a nuclear-powered Mars rover that is part of NASA's Mars Science Laboratory (MSL) mission. The MSL spacecraft—with its payload Curiosity—was launched on 26 November 2011 and successfully landed on Aeolis Palus in Gale Crater on 6 August 2012. Curiosity carries the most advanced payload of scientific gear ever used on the surface of Mars.[1]

Curiosity was designed and built by the Jet Propulsion Laboratory.

Goals and objectives

The Mars Science Laboratory mission has four scientific goals:

  1. Determine whether Mars could ever have supported life
  2. Study the climate of Mars
  3. Study the geology of Mars
  4. Plan for a human mission to Mars

To contribute to these goals, the Curiosity rover has six main scientific objectives:[2][3]

  1. Determine the mineralogical composition of the Martian surface and near-surface geological materials.
  2. Attempt to detect chemical building blocks of life (biosignatures).
  3. Interpret the processes that have formed and modified rocks and soils.
  4. Assess long-timescale (i.e., 4-billion-year) Martian atmospheric evolution processes.
  5. Determine present state, distribution, and cycling of water and carbon dioxide.
  6. Characterize the broad spectrum of surface radiation, including galactic radiation, cosmic radiation, solar proton events and secondary neutrons.

Specifications

  • Dimensions: The Curiosity rover is 3 m (9.8 ft) in length, and weighs 900 kg (2,000 lb), including 80 kg (180 lb) of scientific instruments.[4] It is approximately the size of a Mini Cooper automobile,[5] much larger than the Mars Exploration Rovers, which have a length of 1.5 m (4.9 ft) and weigh 174 kg (384 lb) including 6.8 kg (15 lb) of scientific instruments.[4][6][7]
  • 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. The rover is expected to traverse a minimum of 19 km (12 mi) in its two-year mission.[8]
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.[9][10] Curiosity's RTG is fueled by 4.8 kg (11 lb) of plutonium-238 dioxide supplied by the U.S. Department of Energy,[11] packed in 32 pellets each about the size of a marshmallow.[4]
Curiosity's power generator is the latest RTG generation built by Boeing, called the "Multi-Mission Radioisotope Thermoelectric Generator" or MMRTG.[12] Based on classical RTG technology, it represents a more flexible and compact development step,[12] and is designed to produce 125 watts of electrical power from about 2000 watts of thermal power at the start of the mission.[9][10] 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.[13][14] The power source will generate 2.5 kilowatt hours per day, much more than the Mars Exploration Rovers' solar panels, which can generate about 0.6 kilowatt hours per day.
  • Heat rejection system: The temperatures at the selected landing site 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 rover body so that sensitive components are kept at optimal temperatures.[15] 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.[15]
  • 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.[16] This compares to 3 MB of EEPROM, 128 MB of DRAM, and 256 MB of flash memory used in the Mars Exploration Rovers.[17]
The RCE computers use the RAD750 CPU, which is a successor to the RAD6000 CPU used in the Mars Exploration Rovers.[18][19] The RAD750 CPU is capable of up to 400 MIPS, while the RAD6000 CPU is capable of up to 35 MIPS.[20][21] Of the two on-board computers, one is configured as backup, and will take over in the event of problems with the main computer.[16]
The rover has an Inertial Measurement Unit (IMU) that provides 3-axis information on its position, which is used in rover navigation.[16] The rover's computers are constantly self-monitoring to keep the rover operational, such as by regulating the rover's temperature.[16] 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.[16]
See also: Comparison of embedded computer systems on board the Mars rovers
  • 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.[22] At landing time, 13 minutes, 46 seconds will be required for signals to travel between Earth and Mars.[23]
  • 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.[24] Curiosity's wheels are significantly larger than those used on previous rovers. Each wheel has a pattern which 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" (·--- ·--· ·-··).[25]
  • Wheel size comparison: Sojourner, Mars Exploration Rover, Mars Science Laboratory
    Wheel size comparison: Sojourner, Mars Exploration Rover, Mars Science Laboratory
  • Curiosity rover during mobility testing
    Curiosity rover during mobility testing
  • Tread pattern allows estimation of the distance to imprint. The pattern is Morse code for "JPL", one center that worked on MSL
    Tread pattern allows estimation of the distance to imprint. The pattern is Morse code for "JPL", one center that worked on MSL

Payload

Scientists and engineers use the Mars chamber to test experiments on the SAM instrument.

Unlike earlier rovers, but similar to the Viking landers, Curiosity carries equipment to gather samples of rocks and soil, process them and distribute them to onboard test chambers inside analytical instruments.[1]

  1. MastCam: This system provides multiple spectra and true color imaging with two cameras.[27] The cameras can take true color images at 1600×1200 pixels and up to 10 frames per second hardware-compressed, high-definition video at 720p (1280×720). One camera is the Medium Angle Camera (MAC) which has a 34 mm focal length, a 15-degree field of view, and can yield 22 cm/pixel scale at 1 km. The other camera is the Narrow Angle Camera (NAC) which has a 100 mm focal length, a 5.1-degree field of view, and can yield 7.4 cm/pixel scale at 1 km.[27] Malin also developed a pair of Mastcams with zoom lenses,[32] but these were not included in the final design because of time required to test the new hardware and the looming November 2011 launch date.[33] Each camera has 8 GB of flash memory, which is capable of storing over 5,500 raw images, and can apply real time lossless or JPEG compression.[27] The cameras have an autofocus capability which allows them to focus on objects from 2.1 m (6 ft 11 in) to infinity.[30] Each camera also has a RGB Bayer pattern filter with 8 filter positions.[27] In comparison to the 1024×1024 black and white panoramic cameras used on the Mars Exploration Rover (MER), the MAC MastCam has 1.25× higher spatial resolution and the NAC MastCam has 3.67× higher spatial resolution.[30]
  2. Mars Hand Lens Imager (MAHLI): This system consists of a camera mounted to a robotic arm on the rover, used to acquire microscopic images of rock and soil. MAHLI can take true color images at 1600×1200 pixels with a resolution as high as 14.5 micrometers per pixel. MAHLI has a 18.3 mm to 21.3 mm focal length and a 33.8- to 38.5-degree field of view.[28] MAHLI has both white and ultraviolet LED illumination for imaging in darkness or fluorescence imaging. MAHLI also has mechanical focusing in a range from infinite to millimetre distances.[28] This system can make some images with focus stacking processing.[34] MAHLI can store either the raw images or do real time lossless predictive or JPEG compression.[28] See also Camera, hand lens, and microscope probe
  3. Mars Descent Imager (MARDI): During the descent to the Martian surface, MARDI will take color images at 1600×1200 pixels with a 1.3-millisecond exposure time starting at distances of about 3.7 km to near 5 meters from the ground and will take images at a rate of 5 frames per second for about 2 minutes.[29][35] MARDI has a pixel scale of 1.5 meters at 2 km to 1.5 millimeters at 2 meters and has a 90-degree circular field of view. MARDI has 8 GB of internal buffer memory which is capable of storing over 4,000 raw images. MARDI imaging will allow the mapping of surrounding terrain and the location of landing.[29] JunoCam, built for another spacecraft, is based on MARDI.[36]
  • ChemCam: ChemCam is a suite of remote sensing instruments, including the first laser-induced breakdown spectroscopy (LIBS) system to be used for planetary science and a remote micro-imager (RMI).[37][38] The LIBS instrument can target a rock or soil sample from up to 7 meters away, vaporizing a small amount of it with a 5-nanosecond pulse from a 1067 nm infrared laser and then collecting a spectrum of the light emitted by the vaporized rock. Detection of the ball of luminous plasma will be done in the visible and near-UV and near-IR range, between 240 nm and 800 nm.[37]
Using the same collection optics, the RMI provides context images of the LIBS analysis spots. The RMI resolves 1 mm objects at 10 m distance, and has a field of view covering 20 cm at that distance.[37] The ChemCam instrument suite was developed by the Los Alamos National Laboratory and the French CESR laboratory.[37][39][40][41]
NASA's cost for ChemCam is approximately $10M, including an overrun of about $1.5M,[42] which is less than 1/200th of the total mission costs.[43] The flight model of the Mast Unit was delivered from the French CNES to Los Alamos National Laboratory and was able to deliver the engineering model to JPL in February 2008.[44]
Main article: APXS
  • CheMin: CheMin is the Chemistry and Mineralogy (ChemMin) X-ray diffraction and X-ray fluorescence instrument[48] ChemMin is one of four spectrometers. It will identify and quantify the abundance of the minerals on Mars. It was developed by David Blake at NASA Ames Research Center and the NASA's Jet Propulsion Laboratory.[49] The rover will drill samples into rocks and the resulting fine powder will be sampled by the instrument. A beam of X-rays is then directed at the powder and the internal crystal structure of the minerals deflects back a pattern of X-rays. All minerals diffract X-rays in a characteristic pattern which allows scientists to identify the structure of the minerals the rover will encounter.
  • Sample analysis at Mars (SAM): The SAM instrument suite will analyze organics and gases from both atmospheric and solid samples.[50][51] It was developed by the NASA Goddard Space Flight Center, the Laboratoire Inter-Universitaire des Systèmes Atmosphériques (LISA) of France's CNRS and Honeybee Robotics, along with many additional external partners.[50][52][53] The SAM suite consists of three instruments:
Curiosity landing diagram illustrating the final landing sequence, which utilized the suspension system of Curiosity in order to effect the landing.
  1. The Quadrupole Mass Spectrometer (QMS) detects gases sampled from the atmosphere or those released from solid samples by heating.[50]
  2. The Gas Chromatograph (GC) is used to separate out individual gases from a complex mixture into molecular components. The resulting gas flow will be analyzed in the mass spectrometer with a mass range of 2-535 Daltons.[50]
  3. The Tunable Laser Spectrometer (TLS) performs precision measurements of oxygen and carbon isotope ratios in carbon dioxide (CO2) and methane (CH4) in the atmosphere of Mars in order to distinguish between their geochemical or biological origin.[50][53][54][55]
The SAM also has three subsystems: the 'Chemical separation and processing laboratory', for enrichment and derivatization of the organic molecules of the sample; the sample manipulation system (SMS) for transporting powder delivered from the Curiosity drill to a SAM inlet and into one of 74 sample cups.[50] The SMS then moves the sample to the SAM oven to release gases by heating to up to 1000oC;[50][56] and the pumps subsystem to purge the separators and analysers.

Landing system

Main article: Mars Science Laboratory § Landing system
Artist's concept of Curiosity being lowered by the sky crane from the rocket-powered descent stage.

Previous NASA Mars rovers only became active after the successful entry, descent and landing on the Martian surface. The Mars Science Laboratory, on the other hand, requires six vehicle configurations, 76 pyrotechnic devices, a parachute, retrorockets and a suspension system for the final set-down of the active rover on the surface of Mars.[57]

Curiosity transformed from its stowed flight configuration to a landing configuration while simultaneously lowered beneath the descent stage with a 65 foot (20 m) tether from the "sky crane" system to a soft landing—wheels down—on the surface of Mars.[58][59][60][61] After the rover touched down it waited 2 seconds to confirm that it was on solid ground and fired several pyros (small explosive devices) activating cable cutters on the bridle to free itself from the descent stage. The descent stage then flew away to a crash landing, and the rover prepared itself to begin the science portion of the mission.[62]

See also

References

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  41. ^ ChemCam fact sheet
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Further reading

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