14 December 2004
2009 Mars Rover will be Nuclear Powered
compiled by James C. Foster


The NASA Mars Exploration Program (MEP) will launch a spaceflight mission to Mars in late 2009 that will land a nuclear powered roving Mars Science Laboratory on the surface of the planet.

The long duration rover will be equipped to perform many scientific studies of Mars. The primary scientific objectives of the mission will be to assess the biological potential of at least one target area, characterize the local geology and geochemistry, investigate planetary processes relevant to habitability, including the role of water, and to characterize the broad spectrum of surface radiation. The mission is planned to last at least one martian year (687 days). The landing site has not been chosen, but will be selected based on an assessment of its capacity to sustain life.

The 2009 nuclear rover will be the latest link in a chain of rovers that began with the now primitive 1996 Sojourner rover. Spirit and Opportunity, the current crop of Mars Exploration Rovers, borrowed some of Sojourner's technologies, yet went leaps and bounds above with new technologies of their own.

The main source of power for Spirit and Opportunity comes from a multi-panel solar array. When fully illuminated, the rover solar arrays generate about 140 watts of power for up to four hours per sol (a Martian day). The rover needs about 100 watts (equivalent to a standard light bulb in a home) to drive. Comparatively, the Sojourner roverīs solar arrays provided the 1997 Pathfinder mission with around 16 watts of power at noon on Mars. Thatīs equivalent to the power used by an oven light.

The power system for Spirit and Opportunity includes two rechargeable batteries that provide energy for the rover when the sun is not shining, especially at night. Over time, the batteries will degrade and will not be able to recharge to full power capacity. Also, by the end of the 90-sol mission, the capability of the solar arrays to generate power will likely be reduced to about 50 watts of power due to anticipated dust coverage on the solar arrays (as seen on Sojourner/Mars Pathfinder), as well as the change in season. Mars will drift farther from the sun as it continues on its yearly elliptical orbit, and because of the distance, the sun will not shine as brightly onto the solar arrays. Additionally, Mars is tilted on its axis just like Earth is, giving Mars seasonal changes. Later in the mission, the seasonal changes at the landing site and the lower position of the Sun in the sky at noon than in the beginning of the mission will mean less energy on the solar panels.

The rover twins are in turn paving the way for the next generational leap to the nuclear powered Mars Science Laboratory, scheduled to arrive in 2010. This rover, massive in size and loaded with more science instruments than ever before, is being designed to last longer, rove farther, and with the advantage of nuclear power, enable the rover to conduct more science.

Although the type of RTG's to be used on the 2009 Mars Rover is not known, we can make a safe assumption that they will be similar in performance to the last nuclear powered spacecraft - Cassini. Each of the three RTG's onboard Cassini generates about 290 watts of electric power. The 2009 Rover specifications currently call for two RTG units. If they are identical to the Cassini RTG's then we can expect a total available power level of 580 watts. Now compare that to Spirit and Opportunity's solar power generation of 140 watts and you will see that the 2009 Rover will have over four times the power levels available.

But it's not just about the total amount of electrical generation for the science instruments. It's also the duration of power generation. Spirit and Opportunity max out at 140 watts for up to four hours per day. The nuclear powered rover will have 580 watts of power production available 24 hours and 37 minutes (the length of a martian day) every day. The 2009 Rover's power surplus will allow increased robotic capability that is expected to significantly increase the quality and quantity of science conducted on the Martian surface. Compared to the 2003 MER rovers equipped to travel up to 100 yards a day for three-months, the MSL rover will explore miles of the Red Planet during a multiyear mission, conducting science investigation in less time and with less human oversight than previous Mars rovers.

Spirit and Opportunity were also limited by their solar dependency as to where on Mars they could land and still collect enough sunlight to power their instruments and drive motors. No such limitation will be imposed on the nuclear powered rover, it could even operate at night. And finally, solar powered systems fail much more rapidly. The batteries can only survive so many discharge/recharge cycles. Nuclear powered systems do not use batteries.


NASA Selects Investigations for the Mars Science Laboratory

NASA has selected eight proposals to provide instrumentation and associated science investigations for the mobile Mars Science Laboratory rover, scheduled for launch in 2009. Proposals selected today were submitted to NASA in response to an announcement of opportunity released in April.

The Mars Science Laboratory mission, part of NASA's Mars Exploration Program, would deliver a mobile laboratory to the surface of Mars to explore a local region as a potential habitat for past or present life. The laboratory would operate under its own (nuclear) power. It is expected to remain active for one Mars year, equal to two Earth years, after landing.

In addition to the instrumentation selected, Mars Science Laboratory would carry a pulsed neutron source and detector for measuring hydrogen (including water), provided by the Russian Federal Space Agency. The project would also include a meteorological package and an ultraviolet sensor provided by the Spanish Ministry of Education and Science.

"This mission represents a tremendous leap forward in the exploration of Mars," said NASA's Deputy Associate Administrator for the Science Mission Directorate, Dr. Ghassem Asrar. "MSL is the next logical step beyond the twin Spirit and Opportunity rovers. It will use a unique set of analytical tools to study the red planet for over a year and unveil the past and present conditions for habitability of Mars," Asrar said.

"The Mars Science Laboratory is an extremely capable system, and the selected instruments will bring an analytical laboratory to the martian surface for the first time since the Viking landers over 25 years ago," said Douglas McCuistion, Mars Exploration Program director at NASA Headquarters.

The selected proposals will conduct preliminary design studies to focus on how the instruments can be accommodated on the mobile platform, completed and delivered consistent with the mission schedule. NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Mars Science Laboratory Project for the Science Mission Directorate.

Selected investigations and principal investigators:

  • "Mars Science Laboratory Mast Camera," Michael Malin, Malin Space Science Systems, San Diego, Calif. Mast Camera would perform multi-spectral, stereo imaging at lengths ranging from kilometers to centimeters, and can acquire compressed high-definition video at 10 frames per second without the use of the rover computer.
  • "ChemCam: Laser Induced Remote Sensing for Chemistry and Micro-Imaging," Roger Wiens, Los Alamos National Laboratory, Los Alamos, N.M. ChemCam would ablate surface coatings from materials at standoff distances of up to 10 meters and measure elemental composition of underlying rocks and soils.
  • "Mahli: Mars HandLens Imager for the Mars Science Laboratory," Kenneth Edgett, Malin Space Science Systems. Mahli would image rocks, soil, frost and ice at resolutions 2.4 times better, and with a wider field of view, than the Microscopic Imager on the Mars Exploration Rovers.
  • "The Alpha-Particle-X-ray-Spectrometer for Mars Science Laboratory," Ralf Gellert, Max-Planck-Institute for Chemistry, Mainz, Germany. This instrument would determine elemental abundance of rocks and soil. It will be provided by the Canadian Space Agency.
  • "CheMin: An X-ray Diffraction/X-ray Fluorescence instrument for definitive mineralogical analysis in the Analytical Laboratory of Mars Science Laboratory," David Blake, NASA's Ames Research Center, Moffett Field, Calif. CheMin, would identify and quantify all minerals in complex natural samples such as basalts, evaporites and soils, one of the principle objectives of Mars Science Laboratory.
  • "Radiation Assessment Detector," Donald Hassler, Southwest Research Institute, Boulder, Colo. This instrument would characterize the broad spectrum of radiation at the surface of Mars, an essential precursor to human exploration of the planet. The instrument would be funded by the Exploration Systems Mission Directorate at NASA Headquarters.
  • "Mars Descent Imager," Michael Malin, Malin Space Science Systems. The Mars Descent Imager would poduce high-resolution color-video imagery of the descent and landing phase, providing geological context information, as well as allowing for precise landing-site determination.
  • "Sample Analysis at Mars with an integrated suite consisting of a gas chromatograph mass spectrometer, and a tunable laser spectrometer," Paul Mahaffy, NASA's Goddard Space Flight Center, Greenbelt, Md. This instrument would perform mineral and atmospheric analyses, detect a wide range of organic compounds and perform stable isotope analyses of organics and noble gases.


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