Mars observor Credit - NASA

Mars Observer was a NASA mission to study the surface, atmosphere, interior and magnetic field of Mars from Martian orbit. The mission was designed to operate for one full Martian year (687 Earth days) to permit observations of the planet through its four seasons.

The mission specific objectives were to (1) determine the global elemental and mineralogical character of Mars' surface material, (2) define the planet's global topography and gravitational field, (3) establish the nature of the Martian magnetic field, (4) determine the time and space distribution, abundance, sources and sinks of volatile material and dust over a seasonal cycle, (5) explore the structure and aspects of the circulation of the Martian atmosphere. The spacecraft also carried a radio relay package designed to receive information from the planned Mars Balloon Experiment carried on the planned Soviet Mars '94 mission for retransmission back to Earth. Communications was lost with the spacecraft on 22 August 1993 as it was preparing to go into orbit around Mars, and no significant scientific data was returned. Later investigation indicated this was due to a propulsion system explosion caused by propellants leaking past faulty valves.

The spacecraft was based on Earth-orbiting spacecraft (DMSP and TIROS) and was 3-axis stabilized, zero momentum bias using reaction wheels. Communications with Earth used an X-band system and 1.5 m articulated high gain antenna mounted on a 6-meter boom. The deployed 3.7 x 6.5 meter solar array generated 1.1 - 1.5 kW. The hydrazine and bi-propellant propulsion systems performed trajectory maneuvers, Mars orbit capture and circularization, and orbit maintenance. Deployable booms provided mounting points for instruments. The payloads included:

• Gamma-ray spectrometer (GRS) - designed to measure the abundance of elements (uranium, thorium, potassium, iron and silicon, for example) on the surface of Mars.
• Thermal-emission spectrometer (TES) - intended to map the mineral content of surface rocks, frosts and the composition of clouds.
• Mars Observer Camera (MOC) - a line-scan camera designed to take low-resolution images of Mars on a daily basis for studies of the climate, and medium- and high-resolution images of selected areas to study surface geology and interactions between the surface and the atmosphere. Laser altimeter - intended to measure the topographic relief of the Martian surface.
• Pressure-modulator infrared radiometer (PMIRR) - designed to measure dust and condensates in the atmosphere, as well as profiles of temperature, water vapor and dust opacity as they change with latitude, longitude and season.
• Radio-science investigation - planned to use the spacecraft radio with an ultrastable oscillator to measure atmospheric refractivity as it varies with altitude to determine the temperature profile of the atmosphere, and would use tracking data to measure the gravity field of Mars.
• Magnetometer and electron reflectometer - designed to determine the nature of the magnetic field of Mars, and its interactions with the solar wind.

Design Life: 10 years. Typical orbit: Mars orbit. Length: 3.20 m (10.40 ft). Maximum Diameter: 2.90 m (9.50 ft). Mass: 2,573 kg (5,672 lb).

• 1992 September 25 - Mars Observer - Launch Site: Cape Canaveral. Launch Complex: LC40. Launch Vehicle: Titan. Mass: 2,573 kg (5,672 lb).
  Planned Mars orbiter; lost contact during orbit insertion burn. Solar Orbit (Heliocentric). Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B).

• 1993 August 22 - Communications lost with Mars observor -
  Communications was lost with the spacecraft on August 22, 1993 as it was preparing to go into orbit around Mars, and no significant scientific data was returned. Later investigation indicated this was due to a propulsion system explosion caused by propellants leaking past faulty valves.