December 18

1966 – Saturn's moon Epimetheus is discovered by Richard L. Walker.
1973 – Soyuz 13, crewed by cosmonauts Valentin Lebedev and Pyotr Klimuk, is launched from Baikonur in the Soviet Union.
1999 – NASA launches into orbit the Terra platform carrying five Earth Observation instruments, including ASTER, CERES, MISR, MODIS and MOPITT.