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 ... 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.