|Mission type||radar calibration|
|Operator||MIT Lincoln Laboratory|
|Mission duration||55 years, 10 months and 1 day|
|Spacecraft type||Aluminium sphere|
|Dry mass||34 kg (75 lb)|
|Start of mission|
|Launch date||15:00:03, May 6, 1965 (UTC)|
|Launch site||Cape Canaveral LC-20|
|Contractor||US Department of Defense|
|Deployed from||Geocentric orbit|
|Deployment date||06 May 1965|
|End of mission|
|Decay date||In c. 30000 years|
|Perigee altitude||2,786 km (1,731 mi)|
|Apogee altitude||2,796 km (1,737 mi)|
|RAAN||1 hour 35 minutes|
|Epoch||May 5, 1965|
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 metal sphere. LCS-1 has been used for radar calibration since its launch. It was built by Rohr. Corp. for the MIT Lincoln Laboratory.
LCS-1 is a hollow sphere 1.12 m (3 ft 8 in) in diameter with a wall thickness of 3.2 mm (0.13 in). 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.