An artist's concept of NASA's Mars Odyssey at Mars.

What is Mars Odyssey?

NASA's Mars Odyssey holds the record for the longest continually active spacecraft in orbit around a planet other than Earth. It's been in orbit since Oct. 24, 2001. The spacecraft's main mission is to investigate the Martian environment and to provide key information on hazards future explorers might face.

Nation United States of America (USA)
Objective(s) Mars Orbit
Spacecraft 2001 Mars Odyssey
Spacecraft Mass 3,547 pounds (1,608.7 kilograms)
Mission Design and Management NASA / JPL
Launch Vehicle Delta 7925-9.5 (no. D284)
Launch Date and Time April 7, 2001 / 15:02:22 UT
Launch Site Cape Canaveral, Fla. / SLC-17A
Scientific Instruments 1. Thermal Emission Imaging System (THEMIS)
2. Gamma Ray Spectrometer (GRS)
3. Mars Radiation Environment Experiment (MARIE)
A 3D model of Mars Odyssey. Credit: NASA Visualization Technology Applications and Development (VTAD) › Download Options

Key Dates

Apr. 7, 2001: Launch

Oct. 24, 2001: Mars Orbit Insertion

In Depth: Mars Odyssey

Still in orbit around Mars, 2001 Mars Odyssey holds the record for the longest continually active spacecraft in orbit around a planet other than Earth.

The spacecraft was the first launched as part of NASA’s revamped Mars Exploration Program, which was originally approved in 1993, then restructured in October 2000 after the failures associated with the “faster, better, cheaper” approach.

Mars Odyssey was designed to investigate the Martian environment, providing key information on its surface and the radiation hazards future explorers might face. The goal was to map the chemical and mineralogical makeup of Mars as a step to detecting evidence of past or present water and volcanic activity on Mars.

The spacecraft also was designed to act as a relay for future landers and did so for the Mars Exploration Rovers (Spirit and Opportunity), the Mars Science Laboratory, and the Phoenix lander.

During the coast to Mars, in August 2001, the MARIE radiation instrument failed to respond but was successfully revived by March 2002.

About 200 days after launch, at 02:38 UT Oct. 24, 2001, Mars Odyssey successfully entered orbit around Mars after a 20-minute, 19-second engine burn. The initial orbit was highly elliptical at about 170 × 16,665 miles (272 × 26,818 kilometers). It would take the spacecraft 18.6 hours to complete one circuit.

The spacecraft then implemented an unusual aerobraking maneuver that used the planet’s atmosphere to gradually bring the satellite closer to the Martian surface on every succeeding orbit. This process saved an estimated 440 pounds (200 kilograms) of propellant.

Once the aerobraking was over, by Jan. 30, 2002, Mars Odyssey was in its nearly Sun-synchronous polar orbit of about 250 × 250 miles (400 × 400 kilometers) at 93.1 degree-inclination. The spacecraft’s science and mapping mission started Feb. 19, 2002. This phase lasted 917 Earth days during which entire ground tracks were repeated every two sols.

One of Mars Odyssey’s most exciting findings came early in the mission. In May 2002, NASA announced that the probe had identified large amounts of hydrogen in the soil, implying the presence of ice possibly a mile (meter) below the planet’s surface.

Much later, in March 2008, mission scientists revealed that Mars Odyssey had found evidence of salt deposits in 200 locations in southern Mars. These chloride minerals were left behind in places where water was once abundant.

Having fully completed its primary mission by August 2004, mission planers began a series of extended missions starting Aug. 24, 2004. NASA approved seven two-year extensions in 2004, 2006, 2008, 2010, 2012, 2014, and 2016. Each was dedicated to a specific set of objectives. For example, the fourth extension ending in August 2012 was dedicated to observing the year-to-year variations in polar ice, clouds and dust storms.

One of the spacecraft’s instruments, the MARIE radiation experiment, stopped working Oct. 28, 2003, most likely because of a damaged computer chip.

In addition, one of the spacecraft’s reaction wheels failed in June 2012, but a spare, installed as a redundancy, was activated and spun into service a month later.

In August 2012, NASA used Mars Odyssey’s THEMIS instrument to help select a landing site for the Mars Science Laboratory (MSL) and it later acted as a relay for the MSL rover Curiosity.

By July 2010, NASA was able to announce that Mars Odyssey’s camera had helped construct the most accurate global map of Mars ever, using 21,000 images from the THEMIS instrument. These pictures have been smoothed, matched, blended, and cartographically controlled to make a giant mosaic available to users online.

On Dec. 15, 2010, Mars Odyssey claimed the record for the longest operating spacecraft at Mars, with 3,340 days of operation.

In December 2016, the spacecraft put itself into safe mode due to a problem with orientation relative to Earth and the Sun. By early January 2017, Mars Odyssey was restored to full operating status.

During its many years in Martian orbit, Mars Odyssey globally mapped the amount and distribution of the numerous chemical elements and minerals in the Martian surface and also tracked the radiation environment in low Mars orbit, both necessary before humans can effectively explore the Martian surface.

By mid-2016, the THEMIS instrument had returned more than 208,000 images in visible-light wavelengths and more than 188,000 in thermal-infrared wavelengths.

Additional Resources

NASA: Mars Odyssey

NASA Mars Program: Mars Odyssey

NASA Mars Exploration Program

National Space Science Data Center Master Catalog: Mars Odyssey

Key Source

Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.

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