Phobos 1 and 2 to Mars
(JPEG, 29K)
USSR Mars Lander/Orbiter
Courtesy of NASA's National Space Science Data Center
Mission Statistics:
Launch Date: July 7, 1988 (Phobos 1) and July 21, 1988 (Phobos 2)
Launch Vehicle: Proton
Mass: 2,600 kilograms (5,720 pounds); 6,220 kilograms (13,685 pounds) with orbital insertion hardware attached
Power System: Solar panels
Phobos 1, and its companion spacecraft Phobos 2, were the
next-generation in the Venera-type planetary missions, succeeding those
last used during the Vega 1 and 2 missions to comet
P/Halley.
The objectives of the Phobos missions were to:
- conduct studies of the interplanetary environment;
- perform observations of the Sun;
- characterize the plasma environment in the Martian vicinity;
- conduct surface and atmospheric studies of
Mars; and,
- study the surface composition of the Martian satellite
Phobos.
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-Newton thrusters and
four 10-Newton 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.
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.
Phobos 2 operated nominally throughout its cruise and Mars orbital
insertion phases, gathering data on the Sun, interplanetary medium,
Mars, and Phobos. Contact was lost shortly
before the final phase of the mission, during
which the spacecraft was to approach within 50 meters (110 feet) of
Phobos' surface and release two landers, one a mobile 'hopper', the
other a stationary platform. 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.
Space History