Jet Propulsion Laboratory (U.S.). Mars Observer Project.

The Mars Observer spacecraft was to be the first United States spacecraft to study Mars since the Viking missions in the 1970's. On September 25, 1992, Mars Observer, (formerly known as the Mars Geoscience/Climatology Orbiter Project), was lofted into low Earth orbit at 1:05 p.m. EDT aboard the 145-foot tall Martin Marietta Titan III rocket booster from the Kennedy Space Center's Launch Complex 40, at Cape Canaveral, Florida.

After a 15-minute ride into orbit, the spacecraft was then positioned for its course to Mars by a second rocket booster; the Transfer Orbit Stage (TOS), which fired to break the spacecraft free of Earth's gravity. Technicians had discovered some minor electrical problems in the TOS, which was making its flight debut, in the weeks before launch, but they seemed confident that all was well.

Although the booster performed its tasks of rotating the 5,672- pound spacecraft and speeding it out of Earth orbit, the booster was unable to send communications data verifying the 150-second burn. Ground controllers lost communication with the craft for nearly 90 minutes before the spacecraft was turned on and the 34-meter high efficiency antennas at the Canberra, Australia tracking station acquired a signal. Once the signal was acquired, the spacecraft was out of danger and on its way to a 450-million-mile-journey to Mars.

Approximately 70 minutes into flight, the spacecraft executed commands to deploy its solar array and high-gain antenna in cruise positions. But ground controllers did not receive confirmation from micro-switches on board the spacecraft that the antenna had latched into position until five hours later. They believed that the antenna probably deployed most of the way immediately but did not latch into position until later.

Other minor problems following launch occurred. When the Sun sensors on the solar array did not acquire the Sun, the spacecraft's fault-protection software switched to secondary Sun sensors, which acquired the Sun and operated normally. Also during the first hours after launch, a mysterious torque on the spacecraft occurred which required action of the gyroscope-like reaction wheels to restabilized the spacecraft.

A series of star calibrations also failed on the first day after launch, causing the spacecraft to switch from its normal cruise mode, called the "array normal spin," to a mode in which the spacecraft revolved in relation to the Sun. Ground controllers said this may had been related to forces introduced during the high-gain antenna deployment. They corrected the problem by uplinking a set of commands to return the spacecraft to normal cruise mode. Sets of four trajectory correction maneuvers were planned for Mars Observer during its cruise to Mars. The first took place on Saturday, October 10, 15 days after launch, correcting all errors after injection. Others were scheduled for January 8, 1993, February 8, 1993 and August 9, 1993, 15 days before orbit insertion at Mars.

The Mars Observer mission's scientific goals were to: identify and map the surface chemical and mineral composition of the surface rocks and soil over the whole of Mars, measure the gravity field, search for and characterize a planetary magnetic field, define the topography of the planet recorded over a full Martian year, define the composition, pressure and dynamics of the atmosphere, and determine the seasonal cycles of water, carbon dioxide, and polar caps. This systematic, intense global analysis made Mars Observer one of the most exciting and ambitious efforts undertaken in planetary exploration.

Designed as an orbiting spacecraft, Mars Observer was similar to Earth-orbiting weather and communications satellites and was basically a platform for the science instruments. Just 3 days prior to entering orbit around Mars, after its 11-month scheduled cruise, the $500-million Mars Observer spacecraft fell silent following the pressurization of the rocket thruster fuel tanks. Engineers and mission controllers at NASA's Jet Propulsion Laboratory responded with a series of backup commands to turn on the spacecraft's transmitter and to point the spacecraft's antennas toward Earth. As of 11:00 a.m. EDT on Sunday, August 22, 1993, no signal from the spacecraft had been received by tracking stations around the world.

Because the telemetry transmitted from the Observer had been commanded off and subsequent efforts to locate or communicate with the spacecraft failed, the independent investigation board at the Jet Propulsion Laboratory reported the most probable cause of the lost of communications with the spacecraft on August 21, 1993 was a rupture of the pressurized fuel (monomethyl hydrazine) side of the spacecraft's propulsion system, resulting in a leak of both helium gas and liquid MMH under the spacecraft's thermal blanket.

The gas and liquid would most likely have leaked out from the blanket under pressure in an unsymmetrical manner, resulting in a net spin rate. This high spin rate caused the spacecraft to enter into the "contingency mode," which interrupted the stored command sequence and thus, did not turn the transmitter on. Additionally, this high spin rate precluded proper orientation of the solar arrays, resulting in the discharge nickel-cadmium batteries, each with a capacity of 43-amp-hours. However, the spin effect could have been academic, because the released MMH likely attacked and damaged critical electrical circuits within the spacecraft.

Based on tests preformed at the Jet Propulsion Laboratory, the investigation board's study concluded that an energetically significant amount of nitrogen tetroxide (NTO) and MMH leaked through check values and accumulated in the tubing within the titanium fuel tanks. This probably caused the propulsion system failure. Helium and MMH were released from the tubing, thus forcing the spacecraft into a catastrophic spin and also damaging critical electrical circuits. Also, the board concluded too much reliance had been placed on the heritage of spacecraft hardware, software and procedures of near-Earth missions, which were fundamentally different from the interplanetary Mars Observer Spacecraft.

Dr.Timothy Coffey, Director of Research at the Naval Research Laboratory, Washington, D.C. and an investigation board member, additionally concluded that other possible causes of the loss of the spacecraft were due to: deficiencies in systems engineering/flight rules; the lack of post-assembly procedures for verifying the cleanliness and proper functioning of the propellant pressurization system; failure of the electrical power system due to a regulated power bus short circuit; a current lack of understanding of the differences between the characteristics of European Space Agency and NASA pyro-initiators; and the use of a firm fixed-priced contract restricting the cost-effectiveness and timely development of the unique and highly specialized Mars Observer Spacecraft. The total cost of the Mars Observer mission including development, construction, launch and ground support was estimated at $980 million.

From the description of Mars Observer Project Management and Quarterly Review Reports Collection, 1983-1991. (Jet Propulsion Laboratory Library and Archives). WorldCat record id: 733100814