Science
CALSPHERE 4A
Radar Calibration Sphere · US Air Force
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Calsphere 4A, part of the same family of inert aluminum radar calibration spheres as Calsphere 1 and 2, launched in the mid-1960s. Six decades later it continues performing its original job perfectly — being a precisely known, unchanging shape that radar operators can point at and trust.
Its orbit
- Orbit
- Low Earth Orbitcan appear as a fast-moving star at dawn or dusk
- Altitude
- 668–733 mi (1,075–1,179 km)
- Inclination
- 89.9°
- One orbit
- 107.7 minutes13.4 orbits a day
- NORAD ID
- 01520
- Int’l designator
- 1965-065H
- Launched
- 1965
Orbital elements from CelesTrak, as of 22 Sep 2026.
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