Launched in May 1976, LAGEOS (Laser Geodynamics Satellite) has provided long-term data on key geophysical properties of the Earth, including movement of tectonic plates, and measurement of the planet's gravitational field and the "wobble" in the axis of rotation.
The satellite design was elegantly simple--it carried no onboard sensors, electronics, or moving parts, and was not attitude controlled. It consisted of a brass core surrounded by a sphere of aluminum embedded with 426 cube-corner retroreflectors. Pulsed laser beams transmitted from Earth hit the reflectors and bounce back to ground stations. The travel times are precisely measured, allowing highly accurate measurements of geophysical properties.
At its altitude of 5858 kilometers (3640 miles), the satellite will orbit for thousands of years, which led designers to include a "time capsule" plaque featuring maps of the Earth from 3 different eras: 268 million years in the past, the 1970s, and 8 million years in the future.
This artifact is a 1/2 scale model, donated by R. L. Bullock to the Museum in 1978.
Gift of R.L. Bullock