NASA - JPL | 1992 Mars Observer

Mars Observer was a failed NASA Mars orbiter. Launched in 1992, it was to be the first spacecraft sent to Mars since the 1975 Viking missions, planned to study the planet's geology, geography, climate, and magnetosphere. Due to a failure in the propulsion system pressurization, Mars Observer lost contact with JPL days before MOI (Mars Orbital Insertion), and the mission was subsequently declared lost a few days following planned MOI.

The scientific instruments on Mars Observer included:
TES - Thermal Emission Spectrometer
MOC - Mars Observer Camera
GRS - Gamma Ray Spectrometer
Magnetometer (2x)
Electron reflectometer
MOLA - Mars Observer Laser Altimeter
PMIRR - Pressure Modulator InfraRed Radiometer
as well as a passive radioscience experiment

All of these instruments were later reflown on the Mars Global Surveyor, Mars Climate Orbiter, and 2001 Mars Odyssey, with certain instruments having their names somewhat changed for those missions. On board was also the CNES relay antenna for the Soviet Mars '94 landers, which never flew.

Other notable facts include Mars Observer being launched aboard a Titan IIIC rocket, with the Martin Marietta Transfer Orbit Stage being used to propell it into a Mars transfer orbit, and the bus, attitude control, and a significant amount of other systems, being derived from Earth orbiting satellites, in an attempt to decrease costs and development times. This, however, failed as the budget rose to over $800m before launch.