The Apollo 8 mission marked the first time people navigated away from Earth.
In December 1968, Apollo 8 left Earth orbit and traveled a vast distance to a precise orbit around the Moon. To accomplish this feat, the astronauts used an onboard system that incorporated inertial, radio, and celestial navigation.
Apollo 8 met its goal of orbiting the Moon at an altitude of only 100 kilometers (60 miles) after a journey of almost 400,000 kilometers (250,000 miles)—the farthest humans had ever traveled.
The Apollo 8 crew used sightings on stars, the Moon, and the Earth to update navigational data stored in their Apollo Guidance Computer, which calculated the spacecraft’s velocity and location. The results were compared with data computed by Earth-based tracking stations. MIT’s Instrumentation Laboratory developed this system for NASA.