NAVSTAR 51 (USA 166)

NavigationMilitaryMEOUnited States

NAVSTAR 51 (USA 166) is a navigation satellite, with ownership listed as United States in CelesTrak's catalogue, currently in medium Earth orbit near 19,786 km. It completes one orbit of Earth roughly every 718 minutes at an inclination of 54.9°. It was launched in 2003. Track its live position and see when it passes over your location on azmth.

Orbital data

NORAD ID: 27663
COSPAR ID: 2003-005A
Type: Navigation
Orbit: MEO
Perigee (lowest): 19,786 km
Apogee (highest): 20,594 km
Inclination: 54.86°
Orbital period: 718 min
Launch year: 2003
Owner (CelesTrak): United States

Orbital data updated: 2026-10-18 · from CelesTrak, refreshed every 2 hours.

Who operates it

United StatesLIVEActive

Navigation

GCAT lists it as GPS IIR-8.

Independent assessment

GCAT classes it as a military satellite for navigation and records it as active (17 Oct 2026).

Data: GCAT · CC BY 4.0 Class, mission and status adapted from GCAT by Jonathan McDowell, CC BY 4.0, data update 17 Oct 2026.

Military satellites, counted and explained →

About MEO orbit

Medium Earth Orbit. Between 2,000 and 35,786 km. Home to navigation constellations like GPS (~20,200 km), Galileo, and BeiDou. Orbital period 2 to 24 hours.