NASA - National Aeronautics and Space Administration

The Mars orbiter is a polar-orbiting spacecraft at Mars whose mission fulfilled the Mars science objectives of the failed Mars Observer mission.

Launched with a Delta II vehicle from Cape Canaveral in November 1996, the spacecraft cruised 10 months to Mars, where it was initially inserted into an elliptical capture orbit. During the following 4-month period, thruster firings and aerobraking techniques were used to reach the nearly circular, polar mapping orbit with a 2-hour period. Mapping operations began in late January 1998.

Aerobraking, which used atmospheric drag forces on the spacecraft to remove orbital energy, provided a means of minimizing the amount of fuel required to reach the low Mars orbit.

The spacecraft carried a subset of the Mars Observer instrument payload and used these instruments to acquire data of Mars for a full Martian year (2 Earth years). The spacecraft became a data relay station for signals from U.S. and international landers and low altitude probes for an additional 3 years.

The orbiter was the first mission of a decade-long program of robotic exploration of Mars -- the Mars Surveyor Program. This program provided an aggressive series of orbiters and landers launched in every Mars opportunity. It was affordable, costing about $100 million per year; engaged to the public, with global and close-up images of Mars; had high scientific value; employed a distributed risk strategy so that no single element loss will result in the total loss of data planned in a given opportunity; and used significant advanced technologies.

Landers launched in 1998 and 2001 capitalized on the experiences of the Pathfinder lander mission were launched in 1996. Small orbiters launched in the 1998 and 2001 opportunities carried the remainder of the Mars Observer payload instruments and served as data relay stations.

The spacecraft was acquired from industry through a competitive procurement. The science payload was provided by government-furnished equipment built as copies of the instruments that flew on Mars Observer. JPL managed the project for NASA's Solar System Exploration Division and provided the mission design, navigation and conducted the mission operations. Tracking and data acquisition was provided by a 34-meter subnet of the Deep Space Network.