Twin Rovers (MER)

Spirit

Opportunity

Mission

Twin rovers Spirit and Opportunity are part of NASA's Mars Exploration Rover (MER) mission. They launched on June, 10th and July, 6th 2003 respectively, taking the opportunity of the Mars' opposition that year. Such a configuration is allowing an easy travel to the planet. It occurs each 26 months due to the combined orbits of both the Earth and Mars. En route, both Twin Rovers endured the most intense solar tempest ever recorded. The Twin Rovers' mission is to track the evidence for a life-favourable environment at Mars and to look for a watery past at Gusev Crater and at Meridiani Planum

Rovers Instrumentation

click to a view of rovers' instrumentation and size

Spirit and its twin, Opportunity, are fitted with various science instruments allowing the rovers to act like geologists at Mars. A Panoramic Camera (Pancam) is used to determine the mineralogy, the texture, and the structure of the local terrain. The Pancam is about 5ft above ground allowing too to have a man-height view of the surroundings. Hazcams and Navcams, which are used for navigation, may provide additional views. The second main tool is a robotic arm (the "Instrument Deployment Device", IDD) which bears four more instruments on a turret: a Microscopic Imager (MI) providing close-up images of rocks and soils, a Rock Abrasion Tool (RAT) allowing rocks examination by other instruments, a Mössbauer Spectrometer (MB) dedicated to iron-bearing material, and an Alpha Particle X-Ray Spectrometer (APXS) which is used for the analysis of rocks and soils' elements. Some troubles in rover Spirit's Mössbauer spectrometer were found during the craft's en-route review but this should not impede the rover's efficiency however. The Miniature Thermal Emission Spectrometer (Mini-TES) is associated with the PanCam mast as it allows rocks and soils' identification from afar. Magnets, at last, are used to collect magnetic dust particles or to collect such particles found in the rocks and in the soil. The Twin Rovers have a planned three months mission. They may overcome obstacles as tall as their predecessor the famous little Sojourner, as they may travel as much as 100 yards (100 meters) a day. Rovers are communicating with the Earth either directly, through the high-frequency X-band, or relayed via NASA's two orbiters which are currently around Mars, the Mars Global Surveyor and Mars Odyssey. In both cases data are received by antennas of NASA's Deep Space Network (DSN). The rovers are beaming through their High-Gain Antenna in the first case and through their UHF antenna in the second

As both rovers kept being fit for their mission, NASA extended several times their mission. Dated September 2006, the rovers have been allowed for a further one year of operations. Spirit and Opportunity, at interval, are uploaded with updated flight software, which improve their capacities. Taking in account the longevity of Opportunity, NASA updated the rover, by March 2010, with a new software which will improve the autonomy's ability of it, even in the science field. Now, Opportunity's computer can examine images that the rover takes with its wide-angle navigation camera after a drive, and recognize rocks that meet specified criteria, such as rounded shape or light color. It can then center its narrower-angle panoramic camera on the chosen target and take multiple images through color filters. The system is called Autonomous Exploration for Gathering Increased Science, or AEGIS. Until now, it was ground operators who checked for targets of interest to examine. Previous updates had already allowed both Spirit and Opportunity to choose a route around obstacles, calculate how far to reach out a rover's arm to touch a rock, having the know-how to examine sets of sky images to determine which ones show clouds or dust devils, and then to transmit only the selected images. The AEGIS software lets scientists change the criteria it used for choosing potential targets. In some environments, rocks that are dark and angular could be higher-priority targets than rocks that are light and rounded, for example. Mineral-mapping instrument aboard NASA's new Martian orbiters, like the Martian Reconnaissance Orbiter have been widely improved, with pixel footprint passing from 2 miles (3.2 kilometers) to 60 ft (18 meters) across only as pixel-overlap technique is providing even better resolution still. This is leading during that expanded phase of exploration, to that mineral detections from the orbit is now more frequently used in tactical decisions to where to have a surface rover to move. NASA's Mars Global Surveyor orbiter found an Oklahoma-sized area with a type of the mineral hematite exposed. This discovery motivated selection of the area as Opportunity's 2004 landing site

For more about Mars topography see on this site at "Planetary Basics". For interesting black-and-white/infrared views of both landing places of the Twin Rovers, see at Themis site

for more, see at Twins Rovers site