Mars Climate Orbiter
Overview
 
The Mars Climate Orbiter (formerly the Mars Surveyor '98 Orbiter) was a 338 kilogram (750 lb
LB
-Codes:*.lb, the Internet country code top-level domain for Lebanon*Labrador's former postal abbreviation*Lloyd Aéreo Boliviano airline's IATA code*Luxembourgish language's ISO 639 alpha-2 code*Lebanon's ISO 3166-1 alpha-2 country code...

) robotic
Robotic spacecraft
A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...

 space probe
Space probe
A robotic spacecraft is a spacecraft with no humans on board, that is usually under telerobotic control. A robotic spacecraft designed to make scientific research measurements is often called a space probe. Many space missions are more suited to telerobotic rather than crewed operation, due to...

 launched by 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...

 on December 11, 1998 to study the Martian climate
Climate of Mars
The climate of Mars has been an issue of scientific curiosity for centuries, not least because Mars is the only terrestrial planet whose surface can be directly observed in detail from the Earth....

, atmosphere, surface changes
Martian Surface
The study of surface characteristics is a broad category of Mars science that examines the nature of the materials making up the Martian surface. The study evolved from telescopic and remote-sensing techniques developed by astronomers to study planetary surfaces...

 and to act as the communications relay in the Mars Surveyor '98 program
Mars Surveyor '98 program
The Mars Surveyor '98 program comprised two spacecraft launched separately, the Mars Climate Orbiter and the Mars Polar Lander ; on board the Mars Polar Lander spacecraft were two surface-penetrator probes...

, for 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...

. However, on September 23, 1999, communication with the spacecraft was lost as the spacecraft went into orbital insertion, due to a navigational error.
 
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