The Mars Surveyor 2001 project was a multi-part Mars

Mars

Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

 exploration mission intended as a follow-up to Mars Surveyor 1998. After the two probes of the 1998 project, Mars Climate Orbiter

Mars Climate Orbiter

The Mars Climate Orbiter was a 338 kilogram robotic space probe launched by NASA on December 11, 1998 to study the Martian climate, atmosphere, surface changes and to act as the communications relay in the Mars Surveyor '98 program, for Mars Polar Lander...

 and Mars Polar Lander

Mars Polar Lander

The Mars Polar Lander, also referred to as the Mars Surveyor '98 Lander, was a 290-kilogram robotic spacecraft lander, launched by NASA on January 3, 1999, to study the soil and climate of Planum Australe, a region near the south pole on Mars, as part of the Mars Surveyor '98 mission...

, were both lost, NASA

NASA

The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

's "better, faster, cheaper" exploration philosophy was re-evaluated, with a particular eye on the two 2001 project probes. As a result, the Mars Surveyor 2001 Lander

Mars Surveyor 2001 Lander

The NASA Mars Surveyor 2001 Lander was a planned Mars probe which was canceled in May 2000 in the wake of the failures of the Mars Climate Orbiter and Mars Polar Lander missions in late 1999...

was canceled in May 2000, but the decision was made to go ahead with its orbiter counterpart.

The Mars Surveyor 2001 Orbiter, renamed 2001 Mars Odyssey

2001 Mars Odyssey

2001 Mars Odyssey is a robotic spacecraft orbiting the planet Mars. The project was developed by NASA, and contracted out to Lockheed Martin, with an expected cost for the entire mission of US$297 million. Its mission is to use spectrometers and electronic imagers to hunt for evidence of past or...

, was launched April 7, 2001 reached Mars on October 24, 2001. After aerobraking

Aerobraking

Aerobraking is a spaceflight maneuver that reduces the high point of an elliptical orbit by flying the vehicle through the atmosphere at the low point of the orbit . The resulting drag slows the spacecraft...

 from October 2001 until January 2002, Mars Odyssey began mapping the planet on February 19, 2002.

By December 15, 2010 the orbiter broke the record for longest serving spacecraft at Mars, with 3,340 days of operation, claiming the title from NASA's Mars Global Surveyor

Mars Global Surveyor

The Mars Global Surveyor was a US spacecraft developed by NASA's Jet Propulsion Laboratory and launched November 1996. It began the United States's return to Mars after a 10-year absence. It completed its primary mission in January 2001 and was in its third extended mission phase when, on 2...

, which had arrived sooner than Odyssey but failed in 2006. Some other active orbital missions during this period include Mars Express

Mars Express

Mars Express is a space exploration mission being conducted by the European Space Agency . The Mars Express mission is exploring the planet Mars, and is the first planetary mission attempted by the agency. "Express" originally referred to the speed and efficiency with which the spacecraft was...

 (since 2003) and Mars Reconnaissance Orbiter

Mars Reconnaissance Orbiter

Mars Reconnaissance Orbiter is a NASA multipurpose spacecraft designed to conduct reconnaissance and Exploration of Mars from orbit...

(since 2006), in addition there were a few landers and flybys.