Published: 2012-02-29 20:41:00
Updated: 2012-02-29 20:42:23
Posted February 29, 2012
By Tony Rice
The Mars Odyssey orbiter has circled Mars more than 45,000 times since it arrived ten years ago this month. This time next week, Odyssey will have set a record for longevity at Mars, surpassing its predecessor, the Mars Global Surveyor, which operated from Sept. 11, 1997, to Nov.
At the heart of Odyssey is the Thermal Emission Imaging System (THEMIS). This camera has "proven itself a workhorse," according to Philip Christensen of Arizona State University, Tempe, the camera's principal investigator and designer. "It's especially gratifying to me to see the range of discoveries that have been made using this instrument."
Since going online Feb. 12, 2002, THEMIS has discovered carbon-dioxide gas jets at Mars' south polar ice cap, salt deposits across the planet and a past lake in Aram Chaos, a large crater near the planet's equator. THEMIS is also credited with providing the best global map of Mars to date.
Mars Odyssey completes an orbit of the red planet every two hours.
Over the years, that orbit has been adjusted to put the instruments over interesting parts of the planet earlier in the day to enhance the science that can be gained from this mission.
Getting to Mars isn't simple. The ability to launch a mission to Mars only presents itself every 2 years. This is because of a complex combination of the position of Earth, the position of Mars and the available arsenal of launch vehicles to get spacecraft there. This, combined with the fact that anything that speeds up to escape Earth's gravity and make the 127 million mile journey to Mars has got to slow down, limits when you can go and how long it takes to get there.
Odyssey saught to optimize that with a creative way of making that slow down to ensure a stable Mars orbit. The orbiter spent several months periodically dipping into the Martian atmospshere to create friction to slow the spacecraft to the desired speed, a technique called aerobraking.
NASA has remarkable record of maximizing the science per dollar obtained from Mars missions. The Mars Exploration Rovers were planned for 90 Martian days (also known as sols, each 24.65 Earth hours). The Spirit rover lasted 2210 sols and was declared silent after more than 1300 digital commands were sent in an attempt to wake up the long running rover. Sister rover Opportunity is still rolling along 2880 sols later.
Christensen and his spacecraft are ready to continue challenging MER's longevity. He says, "both Odyssey and THEMIS are in excellent health and we look forward to years more science with them." For more about the Mars Odyssey mission, visit: http://mars.jpl.nasa.gov/odyssey. For more about THEMIS, see http://themis.asu.edu/.
Tony Rice is a volunteer in the NASA/JPL Solar System Ambassador program and software engineer at Cisco Systems. You can follow him on twitter @rtphokie.