Mars Climate Orbiter was designed to function as an interplanetary weather satellite and a communications relay for Mars Polar Lander. Mars Climate Orbiter was lost on arrival at Mars on Sept. 23, 1999. Engineers concluded that the spacecraft entered the planet's atmosphere too low and probably burned up.
Mars Climate Orbiter (MCO) was the second probe in NASA’s Mars Surveyor program, which also included the Mars Global Surveyor (launched in November 1996) and Mars Polar Lander (launched in January 1999).
Mars Climate Orbiter was designed to arrive at roughly the same time as Mars Polar Lander and to conduct simultaneous investigations of Mars’ atmosphere, climate and surface. Arrival in orbit was dated for Sept. 23, 1999. MCO would then reach its operational near-circular Sun-synchronous orbit at about 260 miles (421 kilometers) by Dec. 1, 1999.
The satellite was also designed to serve as a communications relay for the Mars Polar Lander. After the lander’s mission (lasting three months), MCO would have performed a two-year independent mission to monitor atmospheric dust and water vapor and take daily pictures of the planet’s surface to construct an evolutionary map of climatic changes.
Scientists hoped that such information would aid in reconstructing Mars’ climatic history and provide evidence of buried water reserves. After the end of its main mapping mission Jan. 15, 2001, Mars Climate Orbiter would have acted as a communications relay for future NASA missions to Mars.
After launch, the spacecraft was put into a Hohmann transfer orbit to intersect with Mars. It performed four course corrections: Dec. 21, 1998, and March 4, July 25 and Sept. 15, 1999.
At 09:00:46 UT pn Sept. 23, 1999, the orbiter began its Mars orbit insertion burn as planned. The spacecraft was scheduled to re-establish contact after passing behind Mars, but, unfortunately, no signals were received from the spacecraft.
An investigation indicated that the failure resulted from a navigational error due to commands from Earth being sent in English units (in this case, pound-seconds) without being converted into the metric standard (Newton-seconds).
The error caused the orbiter to miss its intended orbit (about 90 miles, or 145 kilometers) and to fall into the Martian atmosphere at approximately 35 miles (56 kilometers) in altitude. The spacecraft disintegrated due to atmospheric stresses.