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| Before the Apollo–Soyuz Test Project (ASTP) took place, American astronauts and Soviet cosmonauts visited each other’s space centers to gain familiarity with the other nation’s spacecraft. The first exchange occurred in July 1973, when the Russian delegation toured the Johnson Space Center. This cover is signed by Alexei Leonov and Thomas Stafford. |
1973-07-09 USA Soviet Cosmonauts Visit Johnson Space Center
