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Planetary News: Mars (2005)Mars Express: Radar Instrument Continues Deployment with Two Primary Booms UpBy A.J.S. RaylJune 16, 2005 The ground team at the European Space Agency's space operations center confirmed earlier today that the second 20-meter [65.6 foot] antenna boom of the MARSIS instrument onboard Mars Express has been successfully and smoothly deployed. The first boom was fully deployed, after a minor glitch, about one month ago. The deployment of the third and final boom begins tomorrow. "This is a great success following some tense moments and careful judgments," said Jean-Jacques Dordain, ESA Director General, in an official statement. The Mars Advanced Radar for Subsurface and Ionosphere Sounding instrument -- known simply as MARSIS -- is the first antenna of its kind and is designed to look below the surface of Mars, as deep as a few miles/kilometers, to see the different layers of material that lie below. Planetary scientists and Mars enthusiasts around the world have been anxiously waiting for the instrument's debut, because it will specifically be on the lookout for reservoirs of underground water, and that may uncover new hints of habitats for possible life. MARSIS features three long antenna booms that broadcast very long wavelength radio waves toward the planet. Those waves will then be reflected back from any surface they encounter and the instrument will observe the time of the reflections, essentially returning 'signatures' of the elements and materials that are hidden underneath, a technique called ground-penetrating radar. It is the same type of radar used on Earth by geologists to prospect for water, oil, rock layers, or rock faults underground. Getting the booms deployed, however, has been a little hair-raising. After deployment of the first boom completed on May 4, however, analysis by the flight controllers at the European Space Operations Center (ESOC), showed that one of the outermost segment had deployed but was not locked into position. The operations team came up with a plan to roll the spacecraft and warm the hinges with the Sun. It worked. Still, ESA officials suspended deployment of the second and third booms until a full analysis and assessment is completed, hence the delay in the operation of the instrument. With this week's deployment of the second boom, the strategy involved using that same technique to heat the hinges both before and after deployment. So, on Monday, shortly before deployment was to begin, Mars Express entered into a slow rotation to last 30 minutes during the boom extension, allowing all the hinges to be properly heated by the Sun. The command to deploy the second boom was then given to the spacecraft, and following that, an autonomous maneuver re-oriented the spacecraft back toward the Sun so the spacecraft could recharge its batteries and the hinges could feel the warmth one more time. The first positive sign reached Earth on Tuesday when Mars Express was able to properly orient itself to transmit data. It took another 48 hours and a series of tests, however, before the team could verify that the long boom was successfully locked, and that the deployment did not affect the integrity of the spacecraft systems. The data that followed in the ensuing hours confirmed bit by bit that the initial spacecraft behavior was consistent with two fully and correctly deployed booms, and that the deployment had not induced disturbance frequencies that may have been dangerous for the spacecraft. In other words, it worked beautifully and the two primary booms are now fully extended. The third, 7-meter [23-foot] 'monopole' boom is scheduled to 'unfold' tomorrow, June 17. Designed to project perpendicularly to the first two booms, this antenna serves to correct some surface roughness effects on the radio waves emitted by MARSIS, and on those reflected by the surface. It is not considered critical, however, because of its orientation and shorter length. So even if it does not work for some reason, MARSIS is already in principle capable of 'looking' beneath the Martian surface for those little pools of water so many scientists believe must be there. Assuming that the third is, as usual, the charm, once the booms are extended and locked into position, ESA engineers will check out the behavior of the orbiter to confirm the overall success of the operation, and MARSIS will undergo a round of commissioning tests - and then the long-awaited observations will begin. By night, it will be used to make soundings for water below the surface. By day, it will probe the structure of the ionosphere. MARSIS, which was developed by the University of Rome, Italy, in partnership with JPL, is one of the seven science experiments carried on board Mars Express and is the last and final one to be deployed. Mars Express is Europe's first, and now one of the most successful missions ever flown to the Red Planet. It launched on June 2, 2003 and entered Mars orbit in December 2003. |
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