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Mission record

Mars Climate Orbiter

Also known as MCO

NASA, JPL · Launched

Explore trajectory

Lost · Failure

NASA's Mars Climate Orbiter was to be the first interplanetary weather satellite at Mars and a communications relay for the Mars Polar Lander. Launched 11 December 1998 on a Delta II from Cape Canaveral, it was lost on 23 September 1999 during the Mars Orbit Insertion burn. The Mishap Investigation Board found the root cause was the failure to use metric units in a ground software file, "Small Forces", used in trajectory models: thruster impulse data was delivered in pound-seconds instead of the specified newton-seconds, low by a factor of 4.45, driving the spacecraft roughly 170 km lower than planned at Mars arrival.

Destinations
Mars
Launch vehicle
Delta II 7425
Launch site
Space Launch Complex 17A, Cape Canaveral Air Station, Florida
Countries
United States
Mission types
Orbiter

Chronology

Mission timeline

  1. Launch

    Launch on a Delta II from Cape Canaveral

    The MCO was launched December 11, 1998 at 18:45:51 UTC (1:45:51 p.m. Eastern Standard Time) atop a Delta II launch vehicle from Launch Complex 17 at Cape Canaveral Air Station, Florida. The vehicle was a Delta 7425 (a Delta II with four solid strap-ons and a Thiokol Star 48B third stage) and the pad was Space Launch Complex 17A.

    Earth

  2. Milestone

    Trajectory Correction Maneuver 4 executed

    TCM-4, the final planned interplanetary trajectory correction, was computed on 8 September 1999 and executed as planned on 15 September 1999. It was expected to place first periapse altitude after MOI at 226 km. Over the following week, orbit determination indicated the first periapse distance had decreased to 150-170 km, and about one hour before MOI it was calculated as low as 110 km, against a minimum survivable altitude of 80 km. TCM-5, an optional fifth maneuver, was not performed.

  3. Orbit insertion

    Mars Orbit Insertion burn begins

    The MOI engine start was recorded at 09:00:46 UTC on 23 September 1999. This timestamp is an Earth-received time; the burn began at the spacecraft approximately 11 minutes earlier, by the one-way light time to Mars. All systems performed nominally until occultation loss of signal four minutes later. After-the-fact navigation estimates using corrected small-forces velocity changes indicated an initial periapsis of 57 km, judged too low for spacecraft survival.

    Mars

  4. Loss of contact

    Loss of signal at Mars occultation entry

    The spacecraft's carrier signal was last seen at approximately 09:04:52 UTC on Thursday, 23 September 1999, at Mars occultation loss of signal, which occurred 49 seconds earlier than predicted. This timestamp is an Earth-received time; occultation entry at Mars occurred approximately 11 minutes earlier, by the one-way light time. Signal was not reacquired following the 21-minute predicted occultation interval.

    Mars

  5. Mission end

    Recovery attempts abandoned

    Exhaustive attempts to reacquire the signal continued through 25 September 1999 but were unsuccessful.

    Mars

  6. Milestone

    Units error discovered

    On 29 September 1999 it was discovered that the small-forces velocity changes reported for use in orbit determination were low by a factor of 4.45 (1 pound force = 4.45 newtons), because the impulse bit data in the Angular Momentum Desaturation file was delivered in lb-sec instead of the specified and expected newton-sec.

  7. Milestone

    Mishap Investigation Board Phase I Report released

    The Mars Climate Orbiter Mishap Investigation Board issued its Phase I Report, naming the root cause as "Failure to use metric units in the coding of a ground software file, 'Small Forces,' used in trajectory models", and listing eight contributing causes: undetected mismodeling of spacecraft velocity changes; navigation team unfamiliar with spacecraft; TCM-5 not performed; systems engineering process did not adequately address transition from development to operations; inadequate communications between project elements; inadequate operations navigation team staffing; inadequate training; and verification and validation process did not adequately address ground software.

Mission architecture

Vehicles

  • Mars Climate Orbiter · Orbiter · Lost on 23 September 1999 during Mars orbit insertion; the Mishap Investigation Board concluded it was either destroyed in the atmosphere or re-entered heliocentric space. Launch mass 629 kg total (338 kg spacecraft plus 291 kg fuel)

    Destinations: Mars

Trajectory record

Trajectory dataset not yet available

No verified trajectory dataset is committed for this mission, so Mission Atlas renders no path.

Provenance

Sources

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

Data verified through August 23, 2026