MARS OBSERVER INVESTIGATION REPORT RELEASED


Donald L. Savage
Headquarters, Washington, D.C.              January  5, 1994


James Gately
Naval Research Laboratory, Washington, D.C.



RELEASE: 94-1

     The final report by the independent investigation board on the failure of the Mars Observer spacecraft was delivered today to NASA Administrator Daniel S. Goldin by Dr. Timothy Coffey, Chairman of the board.  Dr. Coffey is Director of Research at the Naval Research Laboratory, Washington, D.C.

     The Mars Observer spacecraft was to be the first U.S. spacecraft to study Mars since the Viking missions 18 years ago.   The Mars Observer spacecraft fell silent just 3 days prior to entering orbit around Mars, following the pressurization of the rocket thruster fuel tanks.

     Because the telemetry transmitted from the Observer had been commanded off and subsequent efforts to locate or communicate with the spacecraft failed, the board was unable to find conclusive evidence pointing to a particular event that caused the loss of the Observer.

     However, after conducting extensive analyses, the board reported that the most probable cause of the loss of communications with the spacecraft on Aug. 21, 1993, was a rupture of the fuel (monomethyl hydrazine (MMH)) pressurization side of the spacecraft's propulsion system, resulting in a pressurized 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 under the blanket in an unsymmetrical manner, resulting in a net spin rate.  This high spin rate would cause 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 discharge of the batteries.   However, the spin effect may be academic, because the released MMH would likely attack and damage critical electrical circuits within the spacecraft.

     The board's study concluded that the propulsion system failure most probably was caused by the inadvertent mixing and the reaction of nitrogen tetroxide (NTO) and MMH within titanium pressurization tubing, during the helium pressurization of the fuel tanks.  This reaction caused the tubing to rupture, resulting in helium and MMH being released from the tubing, thus forcing the spacecraft into a catastrophic spin and also damaging critical electrical circuits.

     Based on tests performed at the Jet Propulsion Laboratory (JPL) Pasadena, Calif., the board concludes that an energetically significant amount of NTO had gradually leaked through check valves and accumulated in the tubing during the spacecraft's 11-month flight to Mars.

     In addition, the report listed other possible causes of the loss of the
spacecraft as:

• failure of the electrical power system, due to a regulated power bus short circuit;
• NTO tank over-pressurization and rupture due to pressurization regulator failure;
• the accidental high-speed ejection of a NASA standard initiator from a pyro valve into the MMH tank or other spacecraft system.

     Other concerns noted by the board included:

• a need to establish a policy to provide adequate telemetry data of all mission-critical events;
• the lack of post-assembly procedures for verifying the cleanliness and proper functioning of the propellant pressurization system;
• a current lack of understanding of the differences between the characteristics of European Space Agency and NASA pyro-initiators;
• the potential for power bus short circuits, due to single component or insulation failure;
• the potential for command and data handling control systems to be disabled by single-part failure;
• the lack of fault protection external to the redundant crystal oscillator (RXO) should one of its two outputs fail;
• the absence of information, in the telemetry, on the actual state of the RXO's backup oscillator;
• deficiencies in systems engineering/flight rules;
• too much reliance placed on the heritage of spacecraft hardware, software and procedures for near-Earth missions, which were fundamentally different from the interplanetary Mars Observer mission; and
• the use of a firm fixed-price contract restricted the cost-effective and
  timely development of the unique and highly specialized Mars Observer
  Spacecraft.

     Dr.  Coffey notes, "We were challenged to conduct an extraordinarily complex investigation in which we had no hard evidence to examine nor communications with the spacecraft.  However, after an extensive analysis covering every facet of the mission, operations and hardware, I believe that we are justified in arriving at the conclusions we have.  If our findings will help to ensure that future missions won't suffer a similar fate, we feel we will have achieved our purpose."

     Dr.  Coffey also expressed his appreciation for the support provided to the investigation board by the six technical teams, other NRL and Air Force Phillips Laboratory contributors, NASA representatives, the JPL Project Team and Investigation Board, and the Martin Marietta Astro Space
technical teams.

     "I commend Dr. Coffey and his team for the thoughtful and thorough research into the tragic loss of the Mars Observer," said Dr. Wesley Huntress, Jr., Associate Administrator for NASA's Office of Space Science, Washington, D.C.  "Their work will help and guide us in formulating a
corrective action plan to help ensure future success as we plan for recovering our Mars science exploration objectives."

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EDITOR'S NOTE:   The Mars Observer Investigation Board Report is available to news media representatives by calling the NASA Headquarters Newsroom at 202/358-1600