Lincoln Calibration Sphere 1

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.^[2][3] The sphere was launched along with the Lincoln Experimental Satellite-2 on a Titan IIIA. It is technically the oldest operational spacecraft^{[note 1]}, 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.^[4][3]

Lincoln Calibration Sphere 1

Names	LCS-1
Mission type	Radar calibration
Operator	MIT Lincoln Laboratory
COSPAR ID	1965-034C
SATCAT no.	01361
Mission duration	Elapsed: 60 years and 7 days
Spacecraft properties
Spacecraft	LCS-1
Spacecraft type	Aluminium sphere
Manufacturer	Rohr Corp.
Dry mass	34 kg (75 lb)
Start of mission
Launch date	May 6, 1965, 15:00:03 (1965-05-06UTC15:00:03) UTC
Rocket	Titan IIIA
Launch site	Cape Canaveral LC-20
Contractor	US Department of Defense
Deployed from	Geocentric orbit
Deployment date	06 May 1965
End of mission
Disposal	Re-Entry
Decay date	In c. 30,000 years
Orbital parameters
Reference system	Geocentric
Regime	Medium Earth
Eccentricity	0.00055
Perigee altitude	2,786 km (1,731 mi)
Apogee altitude	2,796 km (1,737 mi)
Inclination	32.1°
Period	145.6 minutes
RAAN	1 hour 35 minutes
Epoch	May 5, 1965[1]

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).^[3] 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.^[5] Since its launch, I-band measurements have shown periodic deviations that likely correspond to one or more new surface irregularities.^[6]

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.^[7]

Notes

1. The title of "oldest operational spacecraft" can be disputed; for example, Vanguard 1 is an older satellite that is still "operating" as passive atmospheric measurement probe (it can and time-to-time is tracked from the Earth's surface using optical/radar means to study changes in its orbit), although it can be said that Vanguard 1 no longer operates as it was intended to, as it used to be an active satellite and now is a derelict object in orbit. However, there are other satellites that are still actively used and that were also initially intended to be just passive satellites to be followed from the ground by optical or radar means to study changes in their orbit (and thus the very high altitude atmosphere), like Calsphere 1 and 2 (COSPAR 1964-063C, 1964-063E respectively). So LCS-1's claim of being "oldest operational spacecraft" is dubious.