The launch was originally targeted for 12 October 1989, the first day of a 41-day launch period during which the planets were properly aligned for a direct flight to Jupiter. The liftoff was rescheduled for 17 October 1989 to replace a faulty main engine controller for Space Shuttle Main Engine No. 2. It was postponed again until 18 October 1989 because of rain-showers within of Kennedy Space Center's Shuttle Landing Facility. The weather conditions were in violation of the launch commit criteria for a Return To Launch Site (RTLS) landing in the event of an aborted flight.