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 The Titan IIIA or Titan 3A was an American expendable launch system, launched four times in 1964 and 1965, to test the Transtage upper stage which was intended for use on the larger Titan IIIC. The Transtage was mounted atop two core stages deriv ...

. 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 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 dev ...

. 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 Surface roughness or simply roughness is the quality of a surface of not being smooth and it is hence linked to human ( haptic) perception of the surface texture. From a mathematical perspective it is related to the spatial variability structure ...

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 Optical cross section (OCS) is a value which describes the maximum amount of optical flux reflected back to the source. The standard unit of measurement is m2/sr. OCS is dependent on the geometry and the reflectivity at a particular wavelength of ...

of the LCS-1 was measured in L, S, C, X and K

microwave bands Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequencies between 300 MHz and ...

. Four other spheres were also manufactured and measured for comparison to the one in orbit.

Notes

References

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