Mars Observer

Agency

NASA

Country

🇺🇸 USA

Launched

1992-09-25

End Date

1993-08-21

Mass

1,018 kg

Instruments

7 instruments (never operated at Mars)

TES, TES, MAG/ER, MOC camera, PMIRR, MAGER, GRS — none returned science data

Orbit

Never achieved orbit — contact lost during pre-orbit-insertion pressurization

Key Findings

1.No science data returned from Mars — contact lost August 21, 1993, three days before scheduled orbit insertion
2.Failure investigation concluded that hypergolic fuel leaked past a check valve during tank pressurization, likely rupturing the fuel line
3.The loss ended 17 years of unbroken US Mars mission success and prompted a sweeping review of NASA mission risk management
4.Directly drove adoption of the 'faster, cheaper, better' Mars Surveyor program philosophy for subsequent missions

Mission Outcome

Mars Observer was lost on August 21, 1993, three days before it was to enter Mars orbit, when contact was cut off during pressurization of the propulsion system. The $980 million mission failure was the first US Mars setback since Viking and led to profound changes in NASA programme architecture. Its seven science instruments were later re-flown on Mars Global Surveyor and Mars Climate Orbiter.

Sources

[1] NASA NSSDCA — retrieved 2026-06-01
“Contact was lost with Mars Observer on August 21, 1993, 3 days before it was to go into orbit around Mars.”

← All Mars Orbiters