1999 succeeds 1998 and proceeds 2000.
February[]
- February 7: Stardust is launched.
June[]
- June 24: Cassini-Huygens spacecraft makes it’s second flyby of Venus.
July[]
- July 18: Setebos, Stephano, and Prospero are discovered.
- July 31: Lunar Prospector decays.
August[]
- August 18: Cassini-Huygens spacecraft makes a flyby of the Earth-Moon System.
October[]
- October 6: Callirrhoe is discovered.