Mars orbiter

Print edition : March 07, 2014

This image taken by Viking 1 on August 17, 1976, shows water-ice clouds in the Valles Marineris area of equatorial Mars during local morning time. Photo: Jet Propulsion Laboratory, NASA

ODYSSEY, NASA’s oldest Mars orbiter, was launched in 2001 and began its science mission 12 years ago, making it the longest-working spacecraft ever sent to Mars. Its orbit was tweaked in a manoeuvre that took place on February 11. Odyssey team engineers at NASA’s Jet Propulsion Laboratory in Pasadena, California, and Lockheed Martin Space Systems of Denver, Colorado, designed the gentle move to accelerate Odyssey’s drift towards a morning-daylight orbit. The desired change will occur gradually until the intended orbit geometry is reached in November 2015 and another manoeuvre halts the drift.

This orbit change will enable scientists to observe changing ground temperatures after sunrise and sunset in thousands of places on Mars and help them make the first systematic observations of how morning fogs, clouds and surface frost develop in different seasons on the red planet. These observations could yield insight into the composition of the ground and about temperature-driven processes, such as warm-season flows observed on some slopes, and geysers fed by spring thawing of carbon-dioxide ice near Mars’ poles. The instrument that will be used is the Thermal Emission Imaging System (THEMIS) camera, designed at Arizona State University (ASU), Tempe.

Neither Odyssey nor any other NASA Mars orbiter since the Viking Orbiter in the 1970s has flown an orbital pattern with a view of the ground in morning daylight. Earlier NASA orbiters and the European Space Agency’s Mars Express orbiter provided some tantalising views of morning mists on Mars but concentrated on afternoon observation times when views of the surface are less hazy. “We don’t know exactly what we’re going to find when we get to an orbit where we see the morning just after sunrise,” Philip Christensen, THEMIS principal investigator, ASU, said. “We can look for seasonal differences. Are fogs more common in winter or spring? We will look systematically. We will observe clouds in visible light and check the temperature of the ground in infrared.”