Glossary
Definitions
8 definitions
EIRP (Effective Isotropic Radiated Power)
The product of a transmitter's output power and its antenna gain relative to an isotropic radiator, expressed in dBW — the fundamental measure of how much radio frequency power is directed toward the target, used in link budget calculations to determine received signal strength.
EPIRB
Emergency Position Indicating Radio Beacon — a maritime safety device that, when activated (manually or by water immersion), transmits a distress signal at 406 MHz via the COSPAS-SARSAT satellite network to alert rescue authorities of a vessel's identity and GPS position within minutes.
ESA (European Space Agency)
An intergovernmental organisation of 22 European member states with an annual budget of approximately €7.8 billion (2023), responsible for Europe's civil space programme — operating the Copernicus Earth observation, Galileo GNSS, Ariane launch, and science missions — and one of the world's primary funders of space technology R&D.
Earth Observation (EO)
The use of satellite-based sensors — optical cameras, SAR radars, multispectral and hyperspectral imagers — to collect imagery and geospatial data about Earth's surface, atmosphere, and oceans for applications ranging from defence and agriculture to climate monitoring and disaster response.
Electric Propulsion
A spacecraft propulsion technology that uses electric power (from solar arrays) to accelerate propellant ions or plasma to exhaust velocities 10–80× higher than chemical rockets, achieving far greater fuel efficiency (Isp) at the cost of very low thrust — ideal for station-keeping and orbit raising over months.
Elevation Angle
The angle between the horizon and the line of sight from a ground station or user terminal to a satellite, measured in degrees from 0° (horizon) to 90° (directly overhead). Higher elevation angles reduce atmospheric path length, rain fade, and multipath interference — most VSAT systems require a minimum elevation of 5–20°.
End-of-Life (EOL) Disposal
The controlled removal of a satellite from its operational orbit at the end of its mission life — deorbit to atmospheric re-entry within 5 years for LEO satellites (per FCC/IADC rules), or boost to a graveyard orbit ~300 km above GEO for geostationary satellites — to prevent accumulation of long-term orbital debris.
Eutelsat OneWeb
A LEO broadband constellation of 648 satellites at 1,200 km altitude, operated by Eutelsat following its 2023 merger with OneWeb, targeting enterprise, government, and B2B customers globally with a focus on connectivity-as-a-service through telecom operator partners.