|Before Spirit and Opportunity completed their 300-million-mile journey to the red planet, JPL engineers brought the protoype rover to Dryden for testing last summer. The Mojave Desert acted as a stand-in for the rugged Martian surface, allowing engineers to refine systems being used on the twin rovers now at work on their 90-day mission as robotic geologists.
NASA Photo / Tom Tschida
Mars landers on task
By Sarah Merlin
X-Press Assistant Editor
Engineers at the Jet Propulsion Laboratory - and millions of space and science enthusiasts around the globe - have had much to celebrate lately. After historic dual landings, JPL's two Mars Exploration Rovers (MERs) are busy combing the red planet for clues to its distant past and sending back brilliant images and data that will provide the foundation for years of groundbreaking research.
Emotions ran high at JPL mission control in Pasadena, Calif., when, after journeys of some 300 million miles each, MER Spirit touched down Jan. 3 and MER Opportunity duplicated the achievement on Jan. 24.
Since arriving on Mars, the two robotic explorers have been busy setting about the mechanized geology work they will conduct during their 90-day mission. Each is outfitted with a camera capable of 360-degree color views, microscopes and spectrometers - for close-up investigations of mineralogy - and rock abrasion tools that will allow them to dig into the Martian surface.
With help from the rovers, scientists hope to garner new clues about soil content and the potential for the presence of water on Mars. Practically from the moment the rovers begin collecting it, raw (uncalibrated) real-time data has been available not only to project engineers but also for public viewing on the JPL Web site. Public interest in the MERs has been unparalleled in recent NASA history.
Both rovers were launched from Cape Canaveral Air Force Station, Fla., Spirit on June 10, 2003, and Opportunity shortly afterward, on July 7. The two are identically structured and instrumented, but landed at different sites on Mars - Spirit in Gusev Crater and Opportunity in Meridiani Planum - and are exploring regions on opposite sides of the planet. Each is similar to the earlier Pathfinder rover, which visited the red planet in 1997, but is larger, more mobile and equipped with more sophisticated instruments.
Technology proven in the Pathfinder mission was utilized to land and mobilize the twin six-wheeled MERs. Parachutes deployed to slow each spacecraft containing a rover as it approached the Martian surface, and airbags inflated to cushion the landings. On reaching the surface, each lander bounced for some minutes before rolling to a stop. Airbags then deflated and retracted, and large "petals" cocooning the rovers opened. On the ground, JPL engineers directed the rovers to roll off the landing platforms, stand upright and go to work.
|NASA Administrator Sean O'Keefe, joined officials at the Jet Propulsion Laboratory in Pasadena to share the historic news of a successful landing by the Mars Exploration Rover Spirit on Jan. 3.
NASA Photo / Fred Johnson
Each MER has experienced glitches after arriving on Mars but scientists have been able to rehabilitate both successfully. JPL engineers direct the project via NASA's Deep Space Network, with antennas in California and Australia.
Among refinements the current Mars exploratory mission enjoys over past missions by earlier rover models Pathfinder and Sojourner is one enabling mission controllers to remotely reconfigure and reload the rovers' entire software package if necessary, a program element that has already proved well worth efforts to develop and implement it. Spirit experienced computer-memory and communications problems about two and a half weeks after landing, temporarily suspending its ability to transmit data back to JPL. As part of the cure, engineers reformatted the rover's "flash" memory (a type of rewritable electronic memory that retains information even after power is turned off), installing a fresh version of the flight software. Spirit quickly resumed its duties and has functioned well since.
Opportunity experienced a much less significant glitch when engineers determined that an unplanned drawdown of battery power each night on the rover was due to a heater on its robotic arm. A switch designed to overrule the heater's thermostatic control is apparently not functioning properly, but the problem is not inhibiting the rover's ability to make its appointed rounds.
Opportunity's airbags left detailed impressions in the finely textured soil as the spacecraft rolled to a stop in the small crater where it landed. The soil at Opportunity's landing site appears to have different properties than those of the soil where Spirit touched down, and soil near Opportunity was its first target for close-up examination using a microscope and two tools in attempts to detect the soil's composition.
Some project scientists believe that dark-colored granules covering most of the crater's surface were pressed into an underlying layer of powdery, lighter red material when Opportunity's airbags hit. Others hold to a theory that the dark granules are agglomerations that crumbled into the finer, lighter material when disturbed. But Opportunity's first data about the soil at that location suggests to scientists that the dark pebbles and gravel dotting the landing site contain iron oxide hematite - the most tantalizing evidence so far that the site once lay in liquid water. Analysis of the hematite issue is ongoing.
A six-inch plaque commemorating the lost crew of the Space Shuttle Columbia can be seen in a photo transmitted by Spirit. The plaque is mounted on the back of Spirit's high-gain communication antenna.
NASA Photo / Courtesy JPL
In a gesture of respect for human comrades in space exploration, memorials to the crews of Apollo 1 and the space shuttles Challenger and Columbia have been incorporated into the Mars mission.
A six-inch aluminum plaque mounted on the back of Spirit's high-gain antenna commemorates the seven lost crewmembers of Columbia's STS-107 mission. In addition, the area in the vast flatland of the Gusev Crater where Spirit landed has been named the Columbia Memorial Station. Opportunity's landing site in the Meridiani Planum was named Challenger Memorial Station. And three hills surrounding Spirit's landing site have been named in honor of Apollo 1 astronauts Gus Grissom, Ed White and Roger Chaffee, who perished in a 1967 flash fire during launch pad testing at Kennedy Space Center, Fla.
The MERs are part of NASA's Mars Exploration program, a long-term effort that focuses on robotic exploration of the red planet. The program was designed so as to take advantage of each opportunity to launch a craft to Mars when planetary alignment offered the most favorable conditions - about every 26 months. Earth was closer to Mars when the rovers were launched last year than it had been in 60,000 years, giving scientists their best shot at getting weighty aircraft all the way to Earth's neighbor with the limited fuel capacity of current launch technology. Cost of the two rovers is about $820 million. Their names were selected through a student essay contest that drew nearly 10,000 entries.
Additional photos of the Mars rovers and the surface of Mars --
Mars lander Movie Gallery--
Further information on Mars and the Mars Rovers -- (http://marsrovers.jpl.nasa.gov/home/index.html)