Reports on the loss of Mars Observer
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Donald Savage
Headquarters, Washington, D.C.                    August 22, 1993
(Phone:  202/358-1600)
Bob MacMillin
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone:  818/354-5011)
MISSION ADVISORY
MARS OBSERVER SPACECRAFT LOSES COMMUNICATIONS WITH EARTH
On Saturday evening, August 21st, communications were lost with
the Mars Observer spacecraft as it neared to within 3 days of the
planet Mars.  Engineers and mission controllers at NASA's Jet
Propulsion Laboratory (JPL), Pasadena, Calif., 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 22nd, no signal from the spacecraft
had been received by tracking stations around the world.
Mars Observer has an on-board sequence that will issue the proper
commands to execute the critical Mars orbit insertion events on
Tuesday afternoon, August 24th, assuming that the spacecraft is
operating properly.  This on-board sequence is designed to assure
that the spacecraft is captured into Mars orbit even if ground
controllers cannot communicate with the craft.
Communications were lost during an activity in which the tanks in
the propulsion system were being pressurized.  This system will
be used to slow the spacecraft's speed and allow it to be
captured into Mars orbit.  Controllers have no reason to believe
that the propulsion system has not been properly pressurized.
Engineers and mission controllers are continuing with additional
attempts to re-establish communication.  Commands are being
issued every 20 minutes instructing the spacecraft to switch to a
wider beam low-gain antenna and radio its status back to JPL.
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Forwarded from:
PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
                  MARS OBSERVER MISSION STATUS
                         August 22, 1993
                  8 p.m. Pacific Daylight Time
     Engineers are continuing to attempt to reestablish
communication with the Mars Observer spacecraft, after losing
contact with the spacecraft at 6 p.m. Pacific Daylight Time on
Saturday, Aug. 21, three days before the craft's capture in orbit
around Mars.
     The spacecraft's on-board sequence to begin preparing for
orbit insertion was uplinked on Friday, Aug. 20.  Controllers
have no reason to believe that the spacecraft is not carrying out
those instructions even though communication has been
interrupted.  The spacecraft is set to enter orbit around Mars at
approximately 1:30 p.m. PDT on Tuesday, Aug. 24.
     The Jet Propulsion Laboratory Public Information Office will
be closed until 8 a.m. PDT on Monday, Aug. 23.
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MARS OBSERVER orbital elements                         1 Mar 1993
                                                     rev 6 Oct 93
The following are orbital elements for the Mars Observer
spacecraft.  Element sets are given for (1) the interplanetary
cruise from Earth to Mars; (2) for its its initial capture orbit
at Mars and (3) its final mapping orbit at Mars if the mission had
been successful; and (4) for its orbit around the Sun if the
spacecraft did not enter Mars orbit but instead flew by the planet.
These orbital elements are predicts generated by the Mars
Observer Navigation Team.  The actual set of orbital elements
achieved by the spacecraft will deviate somewhat.
_________________________________________________________________
INTERPLANETARY CRUISE
Semi-major axis          197163351.177       km
Eccentricity                     0.23885397  deg
Inclination                      1.294       deg
Argument of periapsis         -173.656       deg
Ascending node                -177.619       deg
Mean anomaly of epoch          110.042       deg
Epoch of elements:  March 18, 1993 18:53:38.38 Ephemeris Time
Coordinate system:  Sun-centered, Earth Mean Orbit and Equinox
  of Epoch J2000
_________________________________________________________________
MARS CAPTURE ORBIT
Semi-major axis              42923.941       km
Eccentricity                     0.907977    deg
Inclination                     89.000       deg
Argument of periapsis          112.990       deg
Ascending node                -106.453       deg
Mean anomaly of epoch         -180.000       deg
Epoch of elements:  August 26, 1993 10:10:52.78 Ephemeris Time
Coordinate system:  Mars-centered, Mars Mean Equator and IAU
  Vector of Epoch
_________________________________________________________________
MARS MAPPING ORBIT
Semi-major axis               3766.159       km
Eccentricity                     0.004049    deg
Inclination                     92.869       deg
Argument of periapsis          -90.0         deg
Ascending node                 261.590       deg
Mean anomaly of epoch            0.000       deg
Epoch of elements:  December 6, 1993 00:00:00.00 Ephemeris Time
Coordinate system:  Mars-centered, Mars Mean Equator and IAU
  Vector of Epoch
_________________________________________________________________
MARS FLYBY (i.e. spacecraft in solar orbit)
Semi-major axis          204968597.          km
Eccentricity                     0.174563502 deg
Period                         585.789       days
True anomaly                  -161.326456    deg
Mean anomaly                  -154.029206    deg
Inclination                      6.670063    deg
Longitude of ascending node     35.511309    deg
Argument of perihelion         -20.363033    deg
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PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
FOR IMMEDIATE RELEASE                             January 5, 1994
     Several potential causes that may have been responsible for
the loss of the Mars Observer spacecraft last August have been
identified by a special review board at the Jet Propulsion
Laboratory.
     The panel, chaired by JPL Deputy Assistant Laboratory
Director Dr. R. Rhoads Stephenson, was appointed by JPL Deputy
Director Larry N. Dumas as required by JPL management
procedures after contact was lost with Mars Observer on August 21
three days before it was to enter orbit around the red planet.
     According to Stephenson, the board's findings are generally
consistent with those of an independent mission failure review
board appointed by NASA Administrator Daniel Goldin and chaired
by Dr. Timothy Coffey of the Naval Research Laboratory.
     NASA is formulating a corrective action plan based on the
independent review board's recommendations.
     "Each of the review teams weighted the various hypotheses
slightly differently, but we came to the same general conclusions
about the loss," said Stephenson.
     The JPL board's report says one of several potential causes
was most likely to have caused the loss:
     -- A breach of the spacecraft's propulsion system, due to
        one of three possible scenarios;
     -- Electrical power loss due to a massive short in the power
        subsystem;
     -- Loss of function that prevented both the spacecraft's
        main and backup computers from controlling the
        spacecraft;
     -- Loss of both the main and backup transmitters due to
        failure of an electronic part.
     Stephenson added that determining the cause of the loss was
especially difficult because the spacecraft was purposely not
transmitting data to Earth at the time of the failure.
     Mars Observer had turned off its transmitter as a
precautionary measure to protect the transmitter tubes from shock
just before it pressurized its onboard propellant tanks on August
21.  Three days later the spacecraft was due to fire its main
engines to place it in orbit around Mars.
     At the end of the tank pressurization, Mars Observer was
supposed to turn its transmitter back on.  Ground controllers,
however, never received a signal.
     The possibility of a propulsion subsystem breach actually
includes three different possible scenarios, the JPL board said:
     -- Liquid oxidizer (nitrogen tetroxide) may have migrated
        past a check valve in the pressurization lines; during
        the tank pressurization, the oxidizer could have been
        forced into lines containing the fuel, liquid
        monomethylhydrazine, causing the line to burst;
     -- The pressure regulator could have failed, causing the
        oxidizer tank to overpressurize and burst;
     -- A small pyrotechnic device, or squib, that was fired to
        open a valve in one of the pressurization system's lines
        could have been ejected from the pyro valve like a bullet
        and damaged the fuel tank.
     Among the other main categories of failure hypotheses, a
massive power subsystem failure could have been caused by a short
at one of the main bus power diodes.
     Loss of function in the spacecraft's computers could have
occurred at the time the pyrotechnic devices, or squibs, were
fired in the propulsion subsystem.  Under this hypothesis, the
squib firing could have generated an electromagnetic pulse that
caused the spacecraft's main command processor to "hang" in a
state in which neither the main or backup computer was able to
control the spacecraft.
     Loss of both the spacecraft's transmitters could have
resulted if a component failed in a control unit which prevented
either of the transmitters from being powered on.
     In addition to its findings on direct causes of the Mars
Observer failure, the JPL board's report also made general
observations and recommendations to improve spacecraft design and
implementation in the future.
     JPL managed the Mars Observer mission for NASA's Office of
Space Science.
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Donald L. Savage
Headquarters, Washington, D.C.             January  5, 1994
(Phone:  202/358-1547)              EMBARGOED UNTIL 1PM EST
James Gately
Naval Research Laboratory, Washington, D.C.
(Phone:  202/767-2541)
RELEASE: 94-1
MARS OBSERVER INVESTIGATION REPORT RELEASED
     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."
                       - end -
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