Gemini XII was the last mission of the Gemini series. There were no manned space flights by Americans in 1967. The launching pad fire, in which three Apollo 1 astronauts perished on January 27, 1967, resulted in major changes in plans and equipment and the year was marked by further tests preparatory to a manned flight to the Moon.

As was the case on the previous four missions, the Gemini XII flight plan called for rendezvous and docking with a target vehicle. But, according to Dr. George Mueller, NASA’s associate administrator for Manned Spaceflight, mastering what NASA called an extravehicular activity (EVA) or spacewalk would be crucial in proving the agency was ready to move ahead with Apollo and achieving the goal of landing a man on the Moon before the end of the decade. “I feel that we must devote the last EVA period in the Gemini Program to a basic investigation of EVA fundamentals,” he said.

To take on the challenges of this crucial flight, NASA assigned a veteran of the longest spaceflight to date and the astronaut who helped ‘write the book’ on orbital rendezvous. The Command Pilot was Jim Lovell who served on the 14-day Gemini VII mission in December 1965. Flying with Lovell was U.S. U.S. Air Force pilot Buzz Aldrin, the first astronaut to have earned a doctorate. In 1963, he was awarded a doctorate in astronautics from the Massachusetts Institute of Technology. His graduate thesis was ‘line-of sight guidance techniques for manned orbital rendezvous.'

Read more: Gemini XII Crew Masters the Challenges of Spacewalks, NASA.

Astronauts James A. Lovell Jr. (leading), command pilot, and Edwin E. Aldrin Jr., pilot, walk up the ramp at Pad 19 after arriving from the Launch Complex 16 suiting trailer during the prelaunch countdown. Moments later they entered the elevator which took them to the white room and the waiting Gemini-12 spacecraft. Liftoff was at 3:46 p.m. (EST), Nov. 11, 1966. [NASA caption for a variant of the first photograph]

In the second photograph, the Gemini spaceflight program concludes as the Gemini XII spacecraft, with astronaut James A. Lovell Jr., command pilot, and Edwin E. Aldrin Jr., pilot, aboard, nears touchdown in the Atlantic Ocean 2.5 nautical miles from the prime recovery ship, USS Wasp. Gemini XII splashed down at 2:21 p.m. (EST), Nov. 11, 1966 following their flawless automatic reentry. Edwin E. Aldrin Jr., pilot, is picked up from the splashdown area by helicopter as James Lovell awaits near the spacecraft below. A happy Gemini XII prime crew arrived aboard the aircraft carrier, USS Wasp to conclude a four-day mission in space.