Phobos 1 Credit - NASA

The 1F spacecraft was flown on the Phobos mission to Mars, consisting of 2 nearly identical spacecraft. The mission included co-operation 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.

Fobos Hopper 'Hopper' surface probe that was to have been deployed on the surface of Phobos on the Fobos-1/2 missions... Credit- Andy Salmon

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 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.

The main section of the spacecraft consisted of a pressurized toroidal electronics section surrounding a modular cylindrical experiment section. Below these were mounted four spherical tanks containing hydrazine for attitude control and, after the main propulsion module was to be jettisoned, orbit adjustment. A total of 28 thrusters (twenty-four 50 N thrusters and four 10 N thrusters) were mounted on the spherical tanks with additional thrusters mounted on the spacecraft body and solar panels. Attitude was maintained through the use of a three-axis control system with pointing maintained with sun and star sensors. Power was generated via solar arrays. The Mars orbit insertion maneuver was performed by a 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. Mass was 2600 Kg in Martian orbit (6220 Kg with orbital insertion hardware attached). The computer had 30 Mbit memory storage. Downlink was via a 2 degree-of-freedom parabolic high gain antenna 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.

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

Typical orbit: Mars orbit, Phobos rendezvous. Mass: 6,220 kg (13,710 lb). Main Engine: KTDU-425A. Associated Launch Vehicle: Proton 8K82K / 11S824F.

• 1988 July 7 - 1F DPS - Program: Mars. Launch Site: Baikonur. Launch Vehicle: Proton.

• 1988 July 7 - Phobos 1 - Program: Mars. Launch Site: Baikonur. Launch Vehicle: Proton. Mass: 6,220 kg (13,710 lb). Perigee: 2,628 km (1,632 mi). Apogee: 130,504 km (81,091 mi). Inclination: 50.80 deg. Period: 3,267.73 min.

  Second of two missions to Mars' moon Phobos; carried 2 landers; planned to enter Mars orbit. Phobos 1 operated nominally until an expected communications session on 2 September 1988 failed to occur. The failure of controllers to regain contact with the spacecraft was traced to an error in the software uploaded on 29/30 August which had deactivated the attitude thrusters. This resulted in a loss of lock on the Sun, resulting in the spacecraft orienting the solar arrays away from the Sun, thus depleting the batteries. Left in solar Orbit (Heliocentric).

• 1988 July 12 - 1F PPS - Program: Mars. Launch Site: Baikonur. Launch Vehicle: Proton.

• 1988 July 12 - 1F DPS - Program: Mars. Launch Site: Baikonur. Launch Vehicle: Proton.

• 1988 July 12 - Phobos 2 - Program: Mars. Launch Site: Baikonur. Launch Vehicle: Proton. Mass: 6,220 kg (13,710 lb). Perigee: 850 km (520 mi). Apogee: 79,750 km (49,550 mi). Inclination: 1.00 deg. Period: 4,590.00 min.

  Fobos

  First of two Mars missions to Mars' moon Phobos; carried two landers; entered Mars orbit 1/29/89; failed 3/27/89; extremely limited science data. Phobos 2 operated nominally throughout its cruise and Mars orbital insertion phases, gathering data on the Sun, interplanetary medium, Mars, and Phobos. Shortly before the final phase of the mission, during which the spacecraft was to approach within 50 m of Phobos' surface and release two landers, one a mobile 'hopper', the other a stationary platform, contact with Phobos 2 was lost. The mission ended when the spacecraft signal failed to be successfully reacquired on 27 March 1989. The cause of the failure was determined to be a malfunction of the on-board computer.

• 1989 March 27 - Contact lost with Phobos 2 probe -

  Phobos 2 operated nominally throughout its cruise and 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.