Apollo 15 postal covers incident in the moon landings, the public's fascination with items flown in space increased, as did their value. Although it was not publicly known until September 1972, 15 of the men who entered space as Apollo Program astronauts, before Apollo 15, had agreed with a West German named Horst Eiermann to autograph 500 philatelic items (postcards and blocks of stamps) in exchange for $2,500. This included a member of each mission between Apollo 7 (1968) and Apollo 13 (1970). These items were not taken into space. Covers were prepared by the crews and flown on Apollo 11, Apollo 13 and Apollo
Apollo program only one of these plans to make it off the drawing board. Dubbed Skylab, it was constructed complete on the ground rather than in space, and launched in 1973 using the two lower stages of a Saturn V. It was equipped with an Apollo Telescope Mount. Skylab's last crew departed the station on February 8, 1974, and the station itself reentered the atmosphere in 1979. The Apollo-Soyuz Test Project also used Apollo hardware for the first joint nation space flight, paving the way for future cooperation with other nations in the Space Shuttle and International Space Station programs. In September