The branch of optics that describes light propagation in terms of rays.
Note 1: Rays are bent at the interface between two dissimilar media, and may be curved in a medium in which the refractive index is a function of position.
Note 2: The ray in geometric optics is perpendicular to the wavefront in physical optics. Synonym ray optics.

See inverse-square law.

A circular orbit in the equatorial plane, any point on which revolves about the Earth in the same direction and with the same period as the Earth's rotation.
Note: An object in a geostationary orbit will remain directly above a fixed point on the equator at a distance of approximately 42,164 km from the center of the Earth, i.e., approximately… (Read More →)

A geosynchronous satellite whose circular and direct orbit lies in the plane of the Earth's equator and which thus remains fixed relative to the Earth; by extension, a satellite that remains approximately fixed relative to the Earth. [NTIA] [RR] [47CFR]

The orbit in which a satellite must be placed to be a geostationary satellite. [NTIA] [RR]

Any orbit about the Earth, which orbit has a period equal to the period of rotation of the Earth about its axis, and in the same sense, i.e., direction, as the rotation of the Earth.

A germanium-based PN- or PIN-junction photodiode.
Note 1: Germanium photodiodes are useful for direct detection of optical wavelengths from approximately 1 m to several tens of m.
Note 2: Germanium-based detectors are noisier than silicon-based detectors. Silicon-based detectors are therefore usually preferred for wavelengths shorter than 1 m. [After FAA]

Abbreviation for Government Emergency Telecommunications Service (GETS).

1. Global Functioning Plane,
2. Generic Framing Procedure.

Gateway General Packet Radio Service Support Node