The digital ranging system that measured the distance to the Apollo spacecraft

132 · Ken Shirriff · April 23, 2022, 5:44 p.m.
.hilite {cursor:zoom-in} a:link img.hilite, a:visited img.hilite { color: #fff;} During the Apollo missions to the Moon, a critical task for NASA was determining the spacecraft's position. To accomplish this, they developed a digital ranging system that could determine the distance to the spacecraft, hundreds of thousands of kilometers away, with an accuracy of about 1 meter. The basic idea was to send a radio signal to the spacecraft and determine how long it takes to return. Since the si...