This research satellite would eventually provide a stable point in the sky to reflect pulses of laser light.
In this historical photo from the U.S. space agency, Goddard's geophysics research satellite, a 906-lb. (411-kg) satellite that looked more like a dimpled cosmic golf ball, is inside the nose cone of this Delta rocket.
The spacecraft, which NASA launched from the Western Test Range in California in 1976, provided a stable point in the sky to reflect pulses of laser light. By timing the return of the laser beam to an accuracy of about one ten-billionth of a second, scientists expected to measure the relative location of participating ground stations within one inch or a few centimeters. These measurements allowed scientists to track and analyze tectonic plate movement and continental drift.
The spacecraft, called the LAser GEOdynamics Satellite (LAGEOS), was the precursor to the current-day Global Positioning System (GPS) system operated by the Defense Department.
Each weekday, SPACE.com looks back at the history of spaceflight through photos (archive).