Phobos 1

Flight plan

The probe was to travel from Earth to Mars in about 200 days. Two mid-course corrections were planned: the first between days 7 and 20, the second between days 185 and 193. These would place it in a highly elliptical Mars orbit, then into a circular observation orbit at 350 km. After dropping the lower propulsion stage, it would rendezvous with Phobos, release a lander from 50 meters altitude, and move to a final equatorial orbit.

Mission profile

The optical coronagraph of the Terek experiment was non-functional from launch. On 2 September 1988, the expected transmission was not received, traced to a faulty key-command sent on 28 August from ground control in Yevpatoria. A technician omitted a single hyphen in a command; the computer that checked code was malfunctioning, and the technician transmitted the command before the computer could be fixed. The alteration deactivated the attitude thrusters, causing loss of Sun lock and battery depletion.

The fatal software instructions were part of a ground-test routine left in the PROMs due to time pressure before launch. A single-character error in an upload sequence executed the command. The error is also attributed to a political argument between Yevpatoria and Moscow over mission control.

Subsequent investigation

An investigation was ordered after the incident. Disciplinary action was postponed until after the Phobos 2 mission to avoid demoralizing that team. IKI director Roald Sagdeev urged the postponement, quoting Lavrenti Beria. The investigation concluded with the dismissal of the ground control commander at Yevpatoria and acknowledgment that the computer system was poorly designed.

Legacy

Phobos 1 failed before achieving its main scientific objectives. The Phobos program as a whole is considered a failure, though the probes discovered previously unknown information about Mars and Phobos during their orbital flights. In 2026, a non-peer-reviewed preprint hypothesized that near-Earth asteroid 1998 KY26 could possibly be Phobos 1, but the authors stated the research did not unequivocally identify it, and the asteroid is still assumed natural.

Did You Know?

• The intent to carry out a Phobos mission was first made public on 14 November 1984.
• Originally a 1986 launch was planned but later moved to 1988.
• The probe carried a hopper that would bounce across Phobos using spring-loaded legs.