Over the past several years, the Mars Science Laboratory spacecraft—from the heat shield to the rover to the supersonic parachute—has gone through extensive and painstaking testing. This Sunday, it will endure its most arduous test yet: entry into the Martian atmosphere, descent though that atmosphere, and, finally, landing on Mars itself. In anticipation of this upcoming milestone, here are some of the best images of MSL's journey from Pasadena and the Jet Propulsion Laboratory to Cape Canaveral and onward to the Red Planet.