Navigation
NAVSTAR 55 (USA 178)
GPS Navigation Satellite (Block IIR-M) · US Space Force
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Navstar 55 (USA 178), launched in 2004, is a Block IIR-M satellite carrying the modernized M-code military signal — a jam-resistant, higher-power signal specifically designed for use in contested electronic warfare environments, where an adversary might attempt to overwhelm ordinary GPS signals with radio noise. The M-code's higher transmission power and spread-spectrum design make it dramatically harder to jam than the civilian GPS signal every smartphone relies on.
Its orbit
- Orbit
- Medium Earth Orbita high vantage point, ideal for navigation
- Altitude
- 12,283–12,807 mi (19,768–20,611 km)
- Inclination
- 54.9°
- One orbit
- 12.0 hours2.0 orbits a day
- NORAD ID
- 28361
- Int’l designator
- 2004-023A
- Launched
- 2004
Orbital elements from CelesTrak, as of 22 Sep 2026.
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