5 avr. 1991 - Space Shuttle Atlantis is launched from Cape Canaveral, Florida and leaves an observatory to study gamma rays in orbit before returning to Earth on April 11. It is followed by Space Shuttle Discovery which is sent to study instruments related to the Strategic Defense Initiative from April 29 to May 6. Space Shuttle Columbia is launched on June 5, carrying the Spacelab into orbit (La bande de temps)