Key Hole (KH) is the designation for a series of American optical reconnaissance satellites:
KH-1 Corona KH-2 Corona KH-3 Corona KH-4 Corona KH-5 Argon KH-6 Lanyard KH-7 Gambit KH-8 Gambit 3 KH-9 Hexagon/Big Bird KH-10 Dorian/Manned Orbiting Laboratory KH-11 Crystal/Kennan KH-12 Improved Crystal/Ikon/Advanced Kennan KH-13 (unofficial designation, sometimes applied to Enhanced Imaging System or Misty)