The Lincoln Calibration Sphere 1, or LCS-1, is a large aluminium sphere in Earth orbit since 6 May 1965. It is still in use, having lasted for over 50 years. The sphere was launched along with the Lincoln Experimental Satellite-2 on a Titan IIIA. It is technically the oldest operational spacecraft , but it has no power supply or fuel; it is merely a passive metal sphere. LCS-1 has been used for

radar calibration Radar is a detection system that uses radio waves to determine the distance ('' ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, we ...

since its launch. It was built by Rohr. Corp. for the

MIT Lincoln Laboratory The MIT Lincoln Laboratory, located in Lexington, Massachusetts, is a United States Department of Defense federally funded research and development center chartered to apply advanced technology to problems of national security. Research and d ...

. LCS-1 is a hollow sphere in diameter with a wall thickness of . The sphere was constructed from two hemispheres, made by spinning sheet metal over a mold. These hemispheres were fastened to an internal, circumferential hoop by 440 countersunk screws, then milled and polished. The initial finish had a surface roughness less than 10 micrometres and was expected to last for five years. Since its launch, I-band measurements have shown periodic deviations that likely correspond to one or more new surface irregularities. Before being launched to orbit, the optical cross section of the LCS-1 was measured in L, S, C, X and K microwave bands. Four other spheres were also manufactured and measured for comparison to the one in orbit.

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Satellites of the United States Satellites orbiting Earth Passive satellites Spacecraft launched in 1965 Radar calibration satellites {{spacecraft-stub