LOS ANGELES, Feb. 9 (Xinhua) -- The U.S. National Aeronautics and Space Administration (NASA) plans to keep using the Mars Reconnaissance Orbiter (MRO) past the mid-2020s, the space agency said on Friday.
"We are counting on Mars Reconnaissance Orbiter remaining in service for many more years," Michael Meyer, lead scientist of NASA's Mars Exploration Program at NASA's Washington headquarters, was quoted as saying in a statement. "It's not just the communications relay that MRO provides, as important as that is. It's also the science-instrument observations. Those help us understand potential landing sites before they are visited, and interpret how the findings on the surface relate to the planet as a whole."
The spacecraft already has worked more than double its planned mission life since launch on August 12, 2005. It reached Mars and went into orbit on March 10, 2006. The mission's extended service provides data relay from assets on Red Planet's surface and observations with its science instruments, despite some degradation in capabilities.
MRO is a critical element for NASA's Mars Program to support other missions for the long haul, so the mission team is finding ways to extend the spacecraft's longevity.
There are many ways to achieve the goal, according to NASA's Jet Propulsion Laboratory (JPL), who partners with Lockheed Martin Space, Denver, in operating the spacecraft. One is increased reliance on a star tracker and less on aging gyroscopes. Another step is wringing more useful life from batteries.
"In flight operations, our emphasis is on minimizing risk to the spacecraft while carrying out an ambitious scientific and programmatic plan," said MRO Project Manager Dan Johnston of JPL.
At Mars, MRO's attitude changes almost continuously, with relation to the Sun and other stars, as it rotates once per orbit to keep its science instruments pointed downward at Mars.
From the orbiter's 2005 launch until last year, it always used an inertial measurement unit, containing gyroscopes and accelerometers, for attitude control.
Earlier this month, the spacecraft completed its final full-swapover test using only stellar navigation to sense and maintain its orientation, without gyroscopes or accelerometers. The project is evaluating the recent test and planning to shift indefinitely to this "all-stellar" mode in March.
"In all-stellar mode, we can do normal science and normal relay," Johnston said. "The inertial measurement unit powers back on only when it's needed, such as during safe mode, orbital trim maneuvers, or communications coverage during critical events around a Mars landing."
The batteries are recharged by the orbiter's two large solar arrays. To increase the battery's capacity and lifespan, the mission team now charges the batteries higher than before.
The project is also planning to reduce the time the orbiter spends in Mars' shadow, when sunlight can't reach the solar arrays, currently for about 40 minutes of every two-hour orbit.
By shifting the orbit to later in the afternoon, mission managers could reduce the amount of time the spacecraft spends in Mars' shadow each orbit.
However, this option to prolong battery life would not be used until after MRO has supported new Mars mission landings in 2018 and 2021 by receiving transmissions during the landers' critical arrival events.
MRO continues to orbit Mars over a full martian year and gather data with all six of the orbiter's science instruments, a decade after what was initially planned as a two-year science mission to be followed by a two-year relay mission.
More than 1,200 scientific publications have been based on MRO observations, said NASA. Two instruments, the High Resolution Imaging Science Experiment (HiRISE) camera and the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) mineral-mapper, were named most often in research papers.