Spacelab is a combination workshop and
laboratory built by ten European
nations for use aboard the U.S. Space Shuttle. Spacelab
began officially in March 1973 when the European Space Research Organization (now incorporated into the European Space Agency) asked interested nations to sign an arrangement for a Space
Laboratory Program. The signersÑAustria, Belgium, Denmark, France, Germany, Italy, the Netherlands, Spain, Switzerland, and the United KingdomÑdesign, fabricate, pay for, test, and deliver Spacelab units, and NASA is responsible for Spacelab operations after delivery. In a typical mission, a unit is placed within the Shuttle's cargo bay. Its personnel, called payload specialists, enter the pressurized work
section through a tunnel from the Shuttle cabin. Another Spacelab section is unpressurized so that materials can be exposed directly to space. This design can be modified, and each Spacelab should be reusable several times. For individual missions, see Space Shuttle.