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CALSPHERE 1

Radar Calibration Sphere · US Navy / Naval Research Laboratory

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Calsphere 1, launched October 6, 1964 from Vandenberg alongside its twin Calsphere 2 — a hollow aluminum sphere with no power source, no electronics, and no moving parts of any kind. Its entire purpose was to give Cold War-era ground radar a perfectly known, unchanging target to calibrate against. More than six decades later, it is still tracked in orbit — outliving the Cold War, the Space Shuttle program, and most satellites launched decades after it.

Its orbit

Orbit
Low Earth Orbitcan appear as a fast-moving star at dawn or dusk
Altitude
597–621 mi (961–999 km)
Inclination
90.2°
One orbit
104.5 minutes13.8 orbits a day
NORAD ID
00900
Int’l designator
1964-063C
Launched
1964

Orbital elements from CelesTrak, as of 22 Sep 2026.

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