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Mission record

Mars Observer

Also known as Mars Geoscience/Climatology Orbiter, MGCO, MarsObserver

NASA-Office of Space Science Applications, Centre National d'Etudes Spatiales, Russian Space Agency · Launched

Explore trajectory

Lost · Failure

Mars Observer, the first of the Observer series of planetary missions, was designed to study the geoscience and climate of Mars. Its primary science objectives were to determine the global elemental and mineralogical character of the surface material, define globally the topography and gravitational field, establish the nature of the Martian magnetic field, determine the distribution and abundance of volatiles and dust over a seasonal cycle, and explore the structure and circulation of the atmosphere. NASA's Deep Space Chronicle places loss of contact at 01:00 UT on August 22, 1993. The failure board report says telemetry did not return at the expected 00:54 GMT ground-reception time after a planned radio-silence interval; NSSDCA gives August 21 at day precision. Contact was never re-established. It remains unknown whether the spacecraft followed its automatic program into Mars orbit or flew past Mars into heliocentric orbit. Although none of the primary objectives were achieved, cruise data were collected until contact was lost.

Destinations
Launch vehicle
Titan III (CT-4)
Launch site
Cape Canaveral, United States
Countries
United States, France, Soviet Union
Mission types
Orbiter

Chronology

Mission timeline

  1. Launch

    Launched on a Titan III (CT-4)

    NSSDCA's launch/orbital information page gives the launch date and time as 1992-09-25T17:05:01Z on a Titan III from Cape Canaveral, United States. The bus and electronics of the Observer series of spacecraft, used to study the terrestrial planets and near-Earth asteroids, were derived from the Satcom-K and DMSP/TIROS spacecraft, and the rectangular bus section was 2.1 x 1.5 x 1.1 m. The same page gives one interplanetary cruise about the Sun, with an epoch start of 1992-09-26 00:00:00 and no epoch stop.

    Earth

  2. Milestone

    Performed trajectory correction maneuver 1

    The Mission Failure Investigation Board report dates TCM-1 to October 9, 1992. The available chronology does not provide the maneuver's full execution epoch or vector delta-v, so this date is an event anchor only and does not define a spacecraft state.

  3. Milestone

    Performed trajectory correction maneuver 2

    The Mission Failure Investigation Board report dates TCM-2 to February 8, 1993. The available chronology does not provide the maneuver's full execution epoch or vector delta-v, so this date is an event anchor only and does not define a spacecraft state.

  4. Milestone

    Performed trajectory correction maneuver 3

    The Mission Failure Investigation Board report dates TCM-3 to March 18, 1993. This was the third of three flown correction maneuvers; only three of four planned corrections were required. The available chronology does not provide the maneuver's full execution epoch or vector delta-v, so this date is an event anchor only and does not define a spacecraft state.

  5. Loss of contact

    Contact lost two days before scheduled Mars orbit entry

    NASA's Deep Space Chronicle reports that contact ceased at 01:00 UT on August 22, 1993. The Mission Failure Investigation Board report gives the pre-insertion timeline: the transponder was intentionally turned off for pressurization, telemetry ceased at its scheduled ground-reception time of 00:40 GMT, and telemetry did not return at the expected 00:54 GMT ground-reception time. The report distinguishes spacecraft event time from ground receipt time. NSSDCA gives August 21 at day precision. These accounts are retained with their differing time references; the failure cause remains inconclusive. It is unknown whether the spacecraft followed its automatic program into Mars orbit or flew past Mars into heliocentric orbit, so no orbit insertion or flyby is asserted.

    Mars

Mission architecture

Vehicles

  • Mars Observer · Orbiter

    Destinations: Mars

Trajectory record

Trajectory dataset not yet available

Known dates and encounters do not uniquely determine a flight path. This mission’s sourced timeline is available above; no verified trajectory is currently published here.

What is needed to reconstruct this path?
  • A frame-qualified position and vector velocity at an epoch, or equivalent complete orbital elements.
  • Finer event-time constraints where required by an orbital reconstruction; the stored day/month/year precision is retained.
  • The actual failed-flight state history. Intended destinations are not evidence that the spacecraft reached them.
  • The JPL complete cruise elements are labeled predictions and have an epoch on the TCM-3 date without a pre/post-burn designation; their two-body Mars-approach check is not an as-flown residual.

Provenance

Sources

Each source is listed once and labeled with the mission, event, trajectory, or destination/body context it supports.

Data verified through October 12, 2026