NASA Design reference missions (1990s) (aug 16, 1981 – dec 3, 1999)
In the 1990s NASA developed several conceptual level human Mars exploration architectures.
NASA Design reference mission 3.0 (DRM 3.0): a study performed by the NASA Mars Exploration Team at the NASA's Johnson Space Center (JSC) in the 1990s.
Added to timeline:
Timeline of Mars