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NTS 2 (P76-4)


The successful launch of NTS-2 (Navigation Technology Satellite) marked the beginning of a new era in navigation and timekeeping history. NTS-2 was launched on 23 June 1977 as the first NAVSTAR GPS Phase I satellite.

NTS-2 technological features included cesium frequency standards, a nickel-hydrogen battery, three-axis gravity-gradient stabilization with momentum-wheel unloading, control of the spacecraft orbit, laser retroreflectors, solar-cell experiments, radiation dosimeters, and a worldwide network for data acquisition. The satellite experiment has verified Einstein's relativistic clock shift.

Nation: USA
Type / Application: Navigation
Operator: US Air Force (USAF) STP (Space Test Program)
Contractors: Naval Research Laboratory (NRL)
Configuration: Gravity Stabilized
Propulsion: Star-26 AKM
Power: 2 deployable solar arrays, batteries
Mass: 431 kg
Orbit: 19545 km × 20187 km × 63.28
Satellite COSPAR Date LS Launch Vehicle Remarks
NTS 2 (P76-4) (ex Timation 4) 1977-053A 23.06.1977 Va SLC-3W Atlas-F SGS-1
Further NTS missions:
Further STP missions:

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