Phobos (space program) - astronomy.

Phobos (space program) - astronomy. I INTRODUCTION Phobos (space program), two space probes that the former Union of Soviet Socialist Republics (USSR) launched in 1988 toward Phobos, the innermost moon of the planet Mars. The USSR launched both Phobos 1 and Phobos 2 in July 1988. The probes were designed to study the sun and Mars as they traveled to Phobos, where they would each deposit a small lander. Phobos 1 failed soon after leaving Earth orbit. Phobos 2 successfully studied the sun and Mars, but failed as it neared Phobos. The Phobos program took place as the Cold War space race between the United States and the USSR began shifting toward cooperation in the post-Cold War era. Western European governments took part, and individual U.S. researchers worked with European and Soviet engineers and scientists. II SPACECRAFT Each Phobos spacecraft weighed 2590 kg (5720 lb) and consisted of a cylindrical scientific instrument section surrounded by a donut-shaped electronics compartment. This electronics compartment had four spherical propellant tanks attached to its bottom edge. A dish-shaped antenna on top permitted radio communication with Earth. Two side-mounted solar panels generated electricity to power the spacecraft's guidance systems and instruments (see Solar Energy). Each spacecraft had 28 rocket thrusters for steering through space and for pointing instruments. Sun and star sensors allowed the guidance computer to determine the spacecraft's position and orientation. The Phobos scientific instruments included an instrument known as Terek that was used for taking X-ray pictures of the sun, an instrument called Termoscan that was used for studying heat radiated by Mars, and a laser for vaporizing samples of Phobos's crust. Sensors would analyze the vapor to determine the chemical composition of the Martian moon. Both spacecraft carried a solar-powered lander designed to spend a year on Phobos. Phobos 2 also carried a battery-powered, 50-kg (110-lb) rover that could hop around the small moon's surface in the moon's weak gravitational field. III MISSION The Phobos mission had three phases: an Earth to Mars cruise, operations while in orbit around Mars, and Phobos operations. Phobos 1 lifted off from the Baikonur Cosmodrome in south central Kazakhstan on July 7, 1988. Phobos 2 launched on July 12. On August 29 controllers uploaded faulty software to Phobos 1, and the software shut off Phobos 1's thrusters. It tumbled, turned its solar panels away from the sun, and lost power. Soviet controllers lost radio contact with Phobos 1 on September 2. Phobos 2 successfully observed the sun during its cruise from Earth to Mars and reached Mars orbit on January 29, 1989. From orbit, Phobos 2 studied Mars's magnetic field, atmosphere, and surface. Phobos 2 flew within 35 km (20 mi) of the moon Phobos on March 21, 1989, beginning gradual approach to its dark, cratered surface. On March 27, however, radio communication ceased. Many analysts believe that the computer failed, allowing the probe to turn its solar panels away from the sun. Others suggest that a meteoroid hit Phobos 2 hard enough to damage or disorient the probe. Phobos 2 returned some useful data about Mars's magnetic field, atmosphere, and surface, but neither Phobos mission was considered a success. Contributed By: David S. F. Portree Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.