Phobos 1, 2

Phobos was a Soviet mission to Mars consisting of 2 nearly identical spacecraft. The mission included cooperation from 14 other nations including Sweden, Switzerland, Austria, France, West Germany, and the United States (who contributed the use of its Deep Space Network for tracking the twin spacecraft). The objectives of the dual mission were to 1) conduct studies of the interplanetary environment, 2) perform observations of the Sun, 3) characterize the plasma environment in the Martian vicinity, 4) conduct surface and atmospheric studies of Mars, and 5) study the surface composition of the Martian satellite Phobos. In support of these objectives, the mission was to perform the first close scientific investigation of and landing on another planet's moon. In addition to their on-board instrument complement, each vehicle carried a lander designed to land on Phobos' surface and perform a number of in-situ measurements. Phobos 2 also carried a second, smaller "hopper" lander designed to land on Phobos and then use its spring loaded legs to move ("hop") about the moon's surface to make chemical, magnetic and gravity observations at different locations. Phobos 1 operated nominally until controllers lost contact with the spacecraft on September 2, 1988 following a routine software upload (before the vehicle entered Mars orbit). Post-failure analysis traced the problem to an erroneous software command that had deactivated the attitude control thrusters, which resulted in the spacecraft orienting the solar arrays away from the Sun, depleting the batteries. Phobos 2 operated nominally throughout its cruise and Mars orbital insertion phases, gathering data on the Sun, interplanetary medium, Mars, and Phobos. Phobos 2 entered Mars orbit on January 29, 1989. Contact with the vehicle was lost on March 27, 1989 shortly before the final phase of the mission during which the spacecraft was to approach within 50 meters of Phobos' surface and release its two landers. The cause of the failure was determined to be a malfunction of the on-board computer.

Spacecraft
Three-axis stabilized. Attitude control via hydrazine propulsion system with 28 thrusters and 4 spherical propellant tanks. Attitude determination via Sun and star sensors. Power generated via solar arrays. Orbit insertion maneuver performed by dedicated propulsion module utilizing used nitric acid and an amine-based fuel, with a 9.86-18.89 kN variable thrust chamber and eight helium pressurized aluminum alloy tanks. After achieving the final orbit, the orbit insertion module was jettisoned, exposing the downward viewing instruments on the main structure. 30 Mbit memory storage. Downlink via 2 degree-of-freedom parabolic HGA at 4 kbits/sec. The larger Phobos landers would have transmitted data directly to Earth at 4-20 bits/sec on 1.672 Ghz to 70 m Soviet dishes. 'Hopper' lander data would have been relayed via the orbiter.

Payload
TV imaging system; 'Hopper' lander - designed to make chemical, magnetic and gravity observations at different locations on Phobos' surface. Only carried by Phobos 2;'DAS' platform lander - carried panoramic stereo TV system, seismometer, magnetometer, X-ray fluorescence spectrometer, alpha particle scattering device, penetrator; thermal infrared spectrometer/radiometer - 1-2 km resolution; near-infrared imaging spectrometer; thermal imaging camera; magnetometers; gamma-ray spectrometers; X-ray telescope; radiation detectors; radar and laser altimeters; Lima-D laser experiment - designed to vaporize material from the Phobos surface for chemical analysis by a mass spectrometer; imaging radar - Only carried by Phobos 1

Country of Origin	USSR
Customer/User	IKI (Space Research Institute - USSR)
Orbit	Phobos 1: Did not achieve Martian orbit and remained on heliocentric trajectory / Phobos 2: Mars orbit insertion on January 29, 1989. Final orbit was 9671 x 9087 km, incl. = 1.0852 deg, period = 7.6597 hr
Related Sites	Phobos Project Information at GSFC

Launch Facts

Name	Int'l Desig.	Date	Site	Vehicle	Orbit	Mass(kg)
Notes
Phobos 1	1988-058A	7/7/88	Tyuratam	SL-12	Solar	6220
1st of 2 missions to Mars' moon Phobos; carried 2 landers; planned to enter Mars orbit; communications failure prevented orbit insertion
Phobos 2	1988-059A	7/12/88	Tyuratam	SL-12	Mars	6220
2nd of 2 Mars missions to Mars' moon Phobos; carried 2 landers; entered Mars orbit 1/29/89; failed 3/27/89; extremely limited science data