Schematic diagram of the planned rover components.

The Mars Science Laboratory (MSL) is a NASA rover scheduled to be launched on September 15, 2009 and perform the first ever precision landing on Mars in July-September of 2010.^[1] This rover will be three times as heavy and twice the width of the Mars Exploration Rovers (MERs) that landed in 2004. It will carry more advanced scientific instruments than any other mission to Mars to date, including analysis of samples scooped up from the soil and drilled powders from rocks. It will also investigate the past or present ability of Mars to support microbial life. The international community will provide several of the instruments onboard.

The MSL rover will be launched by an Atlas V 541 rocket and will be expected to operate for at least 1 martian year (668 Martian sols/686 Earth days) as it explores with greater range than any previous Mars rover.

Goals/Objectives

The MSL has four goals: To determine if life ever arose on Mars, to characterize the climate of Mars, to characterize the geology of Mars, and to prepare for human exploration. To contribute to the four science goals and meet its specific goal of determining Mars' habitability, Mars Science Laboratory has eight sciencific objectives:^[2]

1. Determine the nature and inventory of organic carbon compounds. 2. Inventory the chemical building blocks of life: carbon, hydrogen, nitrogen, oxygen, phosphorous and sulfur. 3. Identify features that may represent the effects of bilological processes. 4. Investigate the chemical, isotopic, and mineralogical composition of the martian surface and near-surface geological materials. 5. Interpret the processes that have formed and modified rocks and soils. 6. Assess long-timescale (i.e., 4-billion-year) martian atmospheric evolution processes. 7. Determine present state, distribution, and cycling of water and carbon dioxide. 8. Characterize the broad spectrum of surface radiation, including galactic radiation, cosmic radiation, solar proton events and secondary neutrons.

History

In September 2006, MSL was approved by NASA for a 2009 launch. Several JPL engineers working on MSL have informally stated that the MSL design will likely be used on future rovers after the first MSL is launched in 2009.

In April 2008, it was reported that the project is $235 million USD, or 24% over budget. The money to compensate this overrun should come from other NASA Mars missions that will need to be cut.^[3]

In August 2008, it was announced that the third MSL workshop would be held to summarize the data on the 7 potential landing sites.^[4] The result of the voting for the third MSL workshop is that the top three candidate sites in order of votes are: the Eberswalde Crater, the Holden Crater, and the Gale Crater.^[5]

In October 2008, MSL is getting closer to a 30% cost overrun and without additional funding may be cancelled if additional funds are not granted by Congress.^[6] Doug McCuistion, director of the Mars Exploration Program at NASA has said that the rover's progress will be assessed again in January, but that he "fully believe that Congress will support [MSL] as we go forward on this because they recognize the importance of the mission as well."^[7]

The MSL after a successful test of the suspension system by the Jet Propulsion Laboratory on August 20, 2008

Specifications

MSL mockup compared with the Mars Exploration Rover and Sojourner rover by the Jet Propulsion Laboratory on May 12, 2008

A comparison of sizes for the Sojourner rover, the Mars Exploration Rovers, the Phoenix Lander and the Mars Science Laboratory.

The MSL Assembly, Test and Launch Operations (ATLO) in the Jet Propulsion Laboratory

Length/Weight

The MSL will have a length of and weigh including of scientific instruments.^[3] It will be the same size as a Mini Cooper automobile.^[8] This compares to the Mars Exploration Rovers (MERs) which will have a length of and weigh including of scientific instruments.^[3][9]

Speed

Once on the surface, the MSL rover will be able to roll over obstacles approaching 75 cm (29 in) in height. Maximum terrain-traverse speed is estimated to be 90 m (295 ft) per hour via automatic navigation, however, average traverse speeds will likely be about 30 m/h (98 ft/h), based on variables including power levels, difficulty of the terrain, slippage, and visibility. MSL is expected to traverse a minimum of in its two-year mission.^[10]

Power source

The rover will be powered by radioisotope thermoelectric generators (RTGs), as used by the successful Mars landers Viking 1 and Viking 2 in 1976. Solar power is not an efficient power source for Mars surface operations because solar power systems cannot operate effectively at high Martian latitudes, in shaded areas, nor in dusty conditions. Furthermore, solar power cannot provide power at night, thus limiting the ability of the rover to keep its systems warm, reducing the life expectancy of electronics. RTGs can provide reliable, continuous power 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.

The proposed power plant will use "next generation" RTG, built by either Boeing?s Multi-mission Radioisotope Thermoelectric Generator (MMRTG), which is a more flexible and compact power system under development and based on conventional RTGs, or Lockheed Martin?s Stirling Radioisotope Generator, which seems more efficient but untested for use in space. The MSL website states that the MMRTG has been chosen and that it has a minimum lifetime of 14 years.^[11] The MSL will generate 2.5 kilowatts hours per day compared to the Mars Exploration Rovers which can generate about 0.6 kilowatts hours per day.^[3]

Computers

The two identical on-board rover computers are called 'Rover Electronics Module' (REM) and they contain special memory to tolerate the extreme radiation environment from space and to safeguard against power-off cycles. Each computer's memory includes 256 MB of DRAM and 2 GB of flash memory both with error detection and correction, and 256 kB of EEPROM.^[12] This onboard memory is roughly 8 times as capable as the one onboard the Mars Exploration Rovers.

The rover carries an Inertial Measurement Unit (IMU) that provides 3-axis information on its position; the device is used in rover navigation to support safe traverses and to estimate the degree of tilt. The rover's computers will constantly self-monitor its systems, communications and thermal stability at all times. Activities such as taking pictures, driving, and operating the instruments will be performed under commands transmitted in a command sequence to the rover from the flight team. In case of problems, the backup computer can be turned on to take over control and continue the mission.

Proposed scientific payload

At present, 10 instruments have been selected for development or production for the Mars Science Laboratory rover:

Cameras (MastCam, MAHLI, MARDI)

All cameras are being developed by Malin Space Science Systems; all share common design components such as on-board electronic imaging processing boxes and 1600x1200 color CCDs.

• MastCam: This system will provide multiple spectra and true color imaging with two-camera stereoscopic (three-dimensional) vision. True-color are at 1200x1200 pixels and up to 10 frames per second hardware-compressed, high-definition video at 1280 x 720. For comparison the Mars Exploration Rover (MER) panoramic cameras can only produce 1024 x 1024 black & white images. Both cameras will have mechanical zoom and can image objects as far away as 1 km at a resolution of 10 cm per pixel.

• Mars Hand Lens Imager (MAHLI): This system will consist of a camera mounted to a robotic arm on the rover. It will be used to acquire microscopic images of rock and soil. Unlike the MI, MAHLI will take true color images at 1600 x 1200 pixels with a resolution as high as 12.5 micrometers per pixel. MAHLI will have both white and UV LED illumination for imaging in darkness or imaging fluorescence. MAHLI will also have mechanical focusing in a range from infinite to mm distances.

Mars Descent Imager (built by Malin Space Science Systems) with Swiss army knife to show scale

• MSL Mars Descent Imager (MARDI): Developed by Malin Space Science Systems.^[13] During the descent to the Martian surface, MARDI will take approximately 500 color images at 1600 x 1200 pixels 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.^[14] MARDI imaging will allow the mapping of surrounding terrain and location of landing.

ChemCam

ChemCam is a remote Laser-induced breakdown spectroscopy (LIBS) system that can target a rock from up to 13 meters away, vaporizing a small amount of the underlying mineral and then collecting a spectrum of the light emitted by the vaporized rock by using a micro-imaging camera with an angular resolution of 80 microradians. It is being developed by the Los Alamos National Laboratory and the French CESR laboratory. An infrared laser with 1067 nm wavelength and a 5 ns pulse will focus on a spot with 1 GW/cm², depositing 30 mJ of energy. Detection will be done between 240 nm and 800 nm.^{[15] [16][17]} In October 2007 NASA announced that they would cap funding for the ChemCam because of a 70% cost overrun and that the instrument has to be built with the money already provided.^[18] 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.^[19]

Alpha-particle X-ray spectrometer (APXS)

This device will irradiate samples with alpha particles and map the spectra of X-rays that are reemitted for determining the elemental composition of samples. It is being developed by the Canadian Space Agency. The APXS is a form of PIXE and which has previously been used by the Mars Pathfinder and the Mars Exploration Rovers.^[20]

CheMin

Chemin stands for "Chemistry & Mineralogy X-Ray Diffraction/X-Ray Fluorescence Instrument". CheMin is a X-ray diffraction/X-ray fluorescence instrument that will quantify minerals and mineral structure of samples. It is being developed by Dr. David Blake at NASA Ames Research Center and the NASA's Jet Propulsion Laboratory.^[21]

Sample Analysis at Mars (SAM)

The SAM instrument suite will analyze organics and gases from both atmospheric and solid samples. It is being 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.^[22][23] The SAM suite consists on three instruments:

• Quadrupole Mass Spectrometer (QMS)
• Gas Chromatograph (GC)
• Laser Spectrometer (TLS)

The Quadrupole Mass Spectrometer (QMS) will detect gases sampled from the atmosphere or those released from solid samples by heating. The Gas Chromatograph (GC) will be used to separate out individual gases from a complex mixture into molecular components with a mass range of 2?235 u. The Tunable Laser Spectrometer (TLS) will perform 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 a geochemical and a biological origin.^[23][24][25]

The SAM also has three subsystems: The Chemical Separation and Processing Laboratory (CSPL), for enrichment and derivatization of the organic molecules of the sample; the Sample Manipulation System (SMS) for transporting powder delievered from the MSL drill to a SAM inlet and into one of 74 sample cups. The SMS then moves the sample to the SAM oven to release gases by heating to up to 1000 ^oC;^[26] and the Wide Range Pumps (WRP) subsystem to purge the QMS, TLS, and the CPSL.

Radiation Assessment Detector (RAD)

This instrument will characterize the broad spectrum of radiation found near the surface of Mars for purposes of determining the viability and shielding needs for human explorers. Funded by the Exploration Systems Mission Directorate at NASA Headquarters and developed by Southwest Research Institute (SwRI) and the extraterrestrial physics group at Christian-Albrechts-Universität zu Kiel, Germany.

Dynamic Albedo of Neutrons (DAN)

A pulsed neutron source and detector for measuring hydrogen or ice and water at or near the martian surface, provided by the Russian Federal Space Agency.

Rover Environmental Monitoring Station (REMS)

Meteorological package and an ultraviolet sensor provided by the Spanish Ministry of Education and Science. It will be mounted on the camera mast and measure atmospheric pressure, humidity, wind currents and direction, air and ground temperature and ultraviolet radiation levels.

MSL Entry Descent and Landing Instrumentation (MEDLI)

The MEDLI project?s main objective is to measure aerothermal environments, sub-surface heat shield material response, vehicle orientation, and atmospheric density for the atmospheric entry through the sensible atmosphere down to heat shield separation of the Mars Science Laboratory entry vehicle. The MEDLI instrumentation suite will be installed in the heatshield of the MSL entry vehicle. The acquired data will support future Mars missions by providing measured atmospheric data to validate Mars atmosphere models and clarify the design margins on future Mars missions. MEDLI instrumentation consists of three main subsystems: MEDLI Integrated Sensor Plugs (MISP), Mars Entry Atmospheric Data System (MEADS) and the Sensor Support Electronics (SSE).

Hazard avoidance cameras

The MSL will use two pairs of navigation cameras, a front and rear stereo-pair Hazcams used for autonomous hazard avoidance during rover drives and for safe positioning of the robotic arm on rocks and soils. The cameras will use visible light to capture three-dimensional (3-D) imagery. This imagery safeguards against the rover inadvertently crashing into unexpected obstacles, and works in tandem with software that allows the rover make its own safety choices.

Landing system

Entry, descent and landing sequence of the MSL.

• Guided entry - The MSL will be set down on the Martian surface using a new high-precision entry, descent, and landing (EDL) system that will place it within ten kilometers of an intended target, in contrast to the 150-kilometer error of previous landing systems used on Mars. The rover is folded up within an aeroshell which protects it during the travel through space and during the atmospheric entry at Mars. Much of the reduction of the landing precision error is accomplished by an entry guidance algorithm, similar to that used by the astronauts returning to Earth in the Apollo space program. This guidance uses the lifting force experienced by the aeroshell to "fly out" any detected error in range and thereby arrive at the targeted landing site. In order for the aeroshell to have lift, its center of mass is offset from the axial centerline which results in an off-center trim angle in atmospheric flight, again similar to the Apollo Command Module. This is accomplished by a series of ejectable ballast masses. The lift vector is controlled by four sets of two Reaction Control System (RCS) thrusters that produce approximately 500 N of thrust per pair. This ability to change the pointing of the direction of lift allows the spacecraft to react to the ambient environment, and steer toward the landing zone.

• Parachute descent - Like Viking, Mars Pathfinder and the Mars Exploration Rovers, the Mars Science Laboratory will be slowed by a large parachute. After the entry phase is complete and the capsule has slowed to Mach 2, a supersonic parachute is deployed. The entry vehicle must first eject the ballast mass such that the center of gravity offset is removed.

• Powered descent - Following the parachute deployment, the rover and descent stage drop out of the aeroshell. The descent stage is a platform above the rover with variable thrust mono propellant hydrazine rocket thrusters on arms extending around this platform to slow the descent. Meanwhile, the rover itself is being transformed from its stowed flight configuration to a landing configuration while being lowered beneath the descent stage by the "sky crane" system.

• Sky Crane - Like a large crane on Earth, the sky crane system will lower the rover to a "soft landing" -wheels down- on the surface of Mars. This consists of 3 bridles lowering the rover itself and an umbilical cable carrying electrical signals between the descent stage and rover. At roughly 7.5 meters below the descent stage the "sky crane" system slows to a halt and the rover touches down. After the rover touches down it waits 2 seconds to confirm that it is on solid ground and fires several pyros (small explosive devices) activating cable cutters on the bridle and umbilical cords to free itself from the descent stage. The descent stage promptly flies away to a crash landing, and the rover gets ready to roam Mars. The planned "sky crane" powered descent landing system has never been used in actual missions before.

Proposed landing sites

At the first MSL Landing Site workshop, 33 potential landing sites were identified.^[28] The current engineering constraints call for a landing site less than 45° from the Martian equator and less than 1 km above the reference datum.^[29]

By the second workshop in late 2007, the list had grown to include almost 50 sites. These sites were presented in more detail at the Second MSL Landing Site Workshop,^[30] and the list was reduced to six based on the votes of the members of the science community that were present as well as the votes of the science working group (the PI's of the instruments aboard MSL).^[31] One of the sites, Miyamoto crater (on the southwest corner of Meridiani Planum), was not on the first workshop list and was identified as a desirable landing site on the basis of mineralogical data acquired with CRISM in the time between workshops. Also, the locations of some of the targets have been refined relative to the first list.

At the third workshop in September 2008, the Gale Crater, a landing site proposed for the first workshop, were revived as a contender because of new data.^[32] Also, the North Meridiani site was discarded because a site in ?South Meridiani? (about 100 km south of where the Opportunity rover is) was proposed which had more science value and similar safety. The workshop has published the voting chart for the landing sites.^[5] A final workshop in April 2009 is to select a single top choice from the recommended landing sites.^[33]

References

Further reading

See also

• Exploration of Mars
• Rover (space exploration)
• Atmosphere of Mars
• Life on Mars
• 2007 in spaceflight
• 2008 in spaceflight

External links

• MSL Home Page
• Mars Science Laboratory Mission Profile by NASA's Solar System Exploration
• Malin Space Science Systems
• JPL's Mars Technology Program site
• Mars Science Laboratory Acquisition Program
• Spacecraft: Surface Operations Configuration: Science Instruments: ChemCam
• Overview of the SAM instrument suite
• Short description of EDL system (PDF)
• Next on Mars (Bruce Moomaw, Space Daily, March 9, 2005): An extensive overview of NASA's Mars exploration plans, with many details on the Mars Science Laboratory
• nuclearspace.com overview of MSL
• MSL EDL Video located on YouTube
• Demo of mobility system reported by Planetary Society.

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