Servicing and Repair

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Servicing and Repair

When the space shuttle system became operational in the 1980s, access to space began to take on a whole new outlook. Space was about to become a place to carry out work as well as to explore. A key element in America's newest human-rated space vehicle was the ability to provide access to space on a number of commercial fronts, including in-orbit satellite and spacecraft servicing and repair.

One of the workhorses onboard the shuttle is the robot arm called the Remote Manipulator System (RMS). The RMS is capable of placing large items in or removing them from the shuttle's cargo bay. This 15-meter (50-foot) robot arm was used for a number of satellite repair and retrieval missions during the shuttle's first twenty years of operations.

During shuttle mission 41-C in April 1984, the Long Duration Exposure Facility (LDEF) was left in orbit, deployed by the remote arm. During that same mission, astronauts were able to retrieve the ailing Solar Max satellite and repair it in the payload bay of the shuttle. Later that year two communications satellites stranded in a useless low Earth orbit (LEO) were successfully retrieved and brought back to Earth by the shuttle. Eventually, these two satellites, Westar 6 and India's Palapa B-2, were successfully re-launched and deployed. In 1985 the Syncom IV-3 communications satellite, also stranded in a useless orbit, was retrieved, repaired, and deployed by a shuttle crew in Earth orbit.

In the 1990s, there was a crucial repair mission carried out on the Hubble Space Telescope. Hubble had been deployed in 1990 with what was later discovered to be a flawed imaging system. In December 1993 astronauts carried out an emergency repair mission aboard the shuttle to correct Hubble's fault. During a series of space walks, the crew successfully repaired the imaging system, and the Hubble Space Telescope was able to continue its mission, making many outstanding astronomical discoveries over the next decade.

The shuttle, however, is capable of achieving a maximum altitude of only 1,125 kilometers (700 miles) and is not designed to restart its main engines in order to attain escape velocity beyond LEO. Many satellites, such as communications satellites, are in geosynchronous orbit 35,786 kilometers (22,300 miles) above Earth and require upper stages to boost them from LEO to their geosynchronous orbit and beyond to begin their operational missions. If a satellite failed to operate at this distance, it would be a total loss for its owners. In the early 1980s, business and government started to look at ways of solving this problem. One concept was a variant of a Martin Marietta Aerospace design of an Orbital Transfer Vehicle for a 1980s U.S. space station concept. This vehicle would be able to take an astronaut to geosynchronous orbit to service satellites already in place.

As newer, more powerful geosynchronous satellite systems are built, companies have designed satellites and their upper stages with preventive maintenance in mind.

see also Accessing Space (volume 1); Long Duration Exposure Facility (LDEF) (volume 2); Robotics Technology (volume 2); Satellite Industry (volume 1); Satellites, Types of (volume 1); Search and Rescue (volume 1); Space Shuttle (volume 3).

Nick Proach