Glossary
Definitions
140 definitions
L-band
The 1–2 GHz frequency band used by Inmarsat, Iridium, and GPS for mobile satellite services — valued for its near-omnidirectional reception (small antennas work in any orientation), resilience to rain fade, and global regulatory protection for safety communications like GMDSS and COSPAS-SARSAT distress beacons.
LEO (Low Earth Orbit)
Orbital region between 160 and 2,000 km altitude where most modern satellite constellations operate, offering low latency (15–70 ms) and strong signal strength.
Latency
The one-way propagation delay in a satellite communication link, determined primarily by the satellite's orbital altitude: approximately 240–270 ms for GEO, 70–150 ms for MEO, and 15–70 ms for LEO — a fundamental parameter for real-time applications.
Launch Cadence
The frequency at which a launch provider executes flights, typically measured in launches per year. SpaceX achieved 96 Falcon 9/Heavy launches in 2023 — the highest ever recorded by a single provider — enabling rapid constellation deployment and commercial payload turnaround.
Launch Vehicle
A rocket system designed to transport satellites from Earth's surface to orbit, ranging from small dedicated vehicles for single payloads (Rocket Lab Electron, 300 kg to LEO) to heavy-lift rockets (SpaceX Falcon Heavy, 64 t to LEO).
Launch Window
A defined period during which a rocket can be launched to reach a specific orbit, constrained by the alignment of Earth's rotation, the target orbit's geometry, range safety requirements, and weather conditions — ranging from an instantaneous window (ISS rendezvous) to a multi-hour window for simple LEO insertion.
Light Pollution / Dark Sky
The interference with astronomical observation caused by sunlight reflecting off LEO satellite constellations, creating bright streaks in long-exposure telescope images — a growing concern that has prompted ITU discussions, operator commitments to reduce satellite reflectivity, and the International Astronomical Union's CPS Centre for the Protection of the Dark and Quiet Sky.
Link Budget
A systematic accounting of all gains and losses along a satellite communication path — from transmitter EIRP through free-space path loss and rain fade to receiver G/T — used to verify that the received signal-to-noise ratio meets the demodulator's requirements.
MEO (Medium Earth Orbit)
Orbital region between 2,000 and 35,786 km altitude, used primarily for GNSS navigation constellations (GPS at 20,200 km, Galileo at 23,222 km) and broadband satellites like SES O3b mPOWER at 8,063 km.
MILSATCOM (Military Satellite Communications)
Dedicated satellite communication systems operated by military forces for protected, jam-resistant communications — including the US WGS (Wideband Global SATCOM), UK Skynet, and France's Syracuse constellations — complemented by commercial SATCOM (COMSATCOM) leasing for capacity surge requirements.
Maritime Satellite Connectivity
Satellite communication services for ships at sea — encompassing vessel operational communications, crew welfare internet, safety GMDSS compliance, and IoT sensor data — provided via GEO VSAT (Ku/Ka-band) and increasingly via LEO systems (Starlink Maritime) across the global fleet of 60,000+ commercial vessels.
Mega-constellation
A satellite constellation comprising hundreds to thousands of satellites in LEO, designed to deliver global broadband internet coverage. Starlink (10,000+ satellites) and Eutelsat OneWeb (648 satellites) are the two operational examples as of 2026.
Multi-orbit Networking
An architecture that integrates LEO, MEO, and GEO satellite networks into a unified connectivity solution, routing traffic dynamically across orbit types based on latency, cost, availability, and application requirements — enabling seamless hybrid satellite-terrestrial networks.
Network Operations Centre (NOC)
The facility responsible for real-time monitoring, management, and troubleshooting of a satellite network — tracking performance metrics across all terminals and gateways, allocating bandwidth on demand, managing interference, and coordinating maintenance windows.
New Space
The wave of commercial, venture-capital-backed space companies — SpaceX, Planet Labs, Rocket Lab, Spire, AST SpaceMobile — that from around 2010 disrupted the traditional 'Old Space' government-contractor model by applying agile software development practices, COTS components, and mass production to spacecraft and launch vehicles.
Non-Terrestrial Network (NTN)
A 3GPP-standardised framework integrating satellite and High-Altitude Platform Stations (HAPS) into the 5G network architecture, enabling standard smartphones to connect directly to satellites without specialised hardware — the foundation for Direct-to-Cell services.
On-Board Computer (OBC)
The satellite's central flight computer that executes the flight software, coordinates all spacecraft subsystems, implements autonomous fault detection and recovery (FDIR), manages data storage, and processes commands from the ground control segment.
On-Board Processing (OBP)
The execution of signal processing, routing, or data handling functions on the satellite itself rather than on the ground — including digital beamforming, demodulation/re-modulation, store-and-forward data relay, and emerging edge computing — reducing latency and ground infrastructure requirements.
Orbital Debris
All human-made objects in Earth orbit that no longer serve a useful function, including defunct satellites, spent rocket stages, released mission-related objects, and fragmentation debris from collisions and explosions — totalling over 35,000 trackable objects and an estimated 130 million fragments larger than 1 mm.
Orbital Inclination
The angle between a satellite's orbital plane and Earth's equatorial plane, measured in degrees from 0° (equatorial, as with GEO) to 90° (polar orbit) to 180° (retrograde). Inclination determines the geographic latitude bands a satellite overflies and the ground coverage achievable.
Orbital Period
The time a satellite takes to complete one full orbit around Earth, determined solely by orbital altitude via Kepler's third law: 95 minutes at 550 km LEO, 12 hours at 20,200 km GPS MEO, and 23 hours 56 minutes at 35,786 km GEO.
Orbital Slot
A designated position in geostationary orbit defined by a longitude on the equatorial arc (e.g., 28.2°E), allocated by the ITU to a national administration and then licensed to a satellite operator — a finite and contested resource with significant commercial and strategic value.
Payload
The mission-specific equipment carried by a satellite — cameras, radar systems, or communication transponders — that delivers the actual service, as distinct from the bus that supports it.
Personal Locator Beacon (PLB)
A compact personal emergency transmitter that, when manually activated, broadcasts a 406 MHz distress signal via the COSPAS-SARSAT satellite network to alert rescue authorities of the user's GPS position — used by hikers, climbers, and solo adventurers as a one-way emergency signalling device with no subscription fee.
Phased Array Antenna
An antenna system comprising hundreds or thousands of small radiating elements whose relative signal phases are electronically controlled to steer the beam in any direction without mechanical movement, enabling rapid tracking of LEO satellites.
Prime Contractor
The company with overall responsibility for delivering a satellite system under a single contract — integrating spacecraft design, manufacturing, testing, and launch coordination — typically a large aerospace firm such as Airbus Defence and Space, Thales Alenia Space, Boeing Space, or Lockheed Martin.
Rain Fade
The attenuation of satellite radio signals caused by absorption and scattering by rain droplets in the atmosphere — most severe at Ka-band (18–30 GHz) where a tropical downpour can cause 20+ dB of additional loss, managed through link margin, adaptive coding/modulation, and gateway site diversity.
Rideshare
A launch model where multiple satellite operators share a single rocket, each paying only for their allocated mass fraction, enabling smallsat operators to reach orbit for hundreds of thousands rather than millions of dollars per launch.
Rocket Reusability
The ability to recover and reflight rocket components — primarily first stages — after launch, reducing per-flight costs by amortising the manufacturing cost of the rocket hardware across multiple missions.
S-band
The 2–4 GHz frequency band used in satellite communications for TT&C (telemetry, tracking and command), weather satellites (NOAA, Meteosat), and some mobile satellite services, offering good propagation characteristics with moderate antenna size requirements.
SAR (Synthetic Aperture Radar)
A radar imaging technique that synthesises a large virtual antenna by accumulating echoes from multiple positions along the satellite's flight path, producing high-resolution imagery of Earth's surface regardless of cloud cover, darkness, or weather conditions.
SES O3b mPOWER
SES's second-generation MEO broadband constellation of 11 satellites at 8,063 km altitude, delivering terabit-class capacity with ~130 ms latency via software-defined digital beamforming payloads — targeting mobile network operators, maritime, government, and enterprise customers with committed high-throughput services.
SLA (Service Level Agreement)
A contractual commitment between a satellite service provider and a customer defining minimum performance guarantees — typically availability (99.5–99.99%), latency bounds, committed information rate (CIR), and remedies for breach — that distinguishes enterprise-grade from consumer-grade satellite services.
SOTM (Satcom On The Move)
Satellite communications terminals designed to maintain a continuous link with a satellite while mounted on a moving platform — land vehicles, ships, aircraft, or trains — using motorised tracking antennas or electronically steered phased arrays to compensate for the platform's motion.
SSO (Sun-Synchronous Orbit)
Near-polar retrograde orbit (96–98° inclination) at 600–800 km altitude that precesses 1° eastward per day, ensuring a satellite passes over any given location at the same local solar time — essential for consistent Earth observation imagery.
Satellite Backhaul
The use of satellite links to connect remote cellular base stations (2G/3G/4G/5G) to the core mobile network, enabling mobile coverage in areas where terrestrial fibre or microwave backhaul is unavailable or uneconomical — serving hundreds of millions of mobile users in rural Africa, Asia, and Latin America.
Satellite Broadband
Internet access delivered via satellite to consumers and enterprises in areas without adequate terrestrial connectivity, ranging from GEO VSAT services (25–100 Mbps, 600 ms RTT) to LEO systems like Starlink (100–300 Mbps, 25–60 ms RTT).
Satellite Bus
The structural and functional platform of a satellite that provides power, propulsion, attitude control, thermal regulation, and communications for the mission-specific payload — the spacecraft without its instruments.
Satellite Constellation
A coordinated network of satellites working together as a single system to provide continuous, global or regional coverage, with each satellite handing off service to the next as it passes out of view.
Satellite Cybersecurity
The practice of protecting satellite systems — spacecraft, ground control infrastructure, user terminals, and communication links — against cyberattacks including jamming, spoofing, commanding, eavesdropping, and supply chain compromise, recognised as a national security priority after the Viasat KA-SAT attack in February 2022.
Satellite Modem
The electronic device that modulates (converts digital data to radio signals for uplink) and demodulates (converts received radio signals back to digital data from the downlink) satellite communication signals, implementing the physical layer of a satellite broadband link.
Satellite Operator
A company that owns and operates one or more satellites in orbit, selling or leasing capacity (transponder bandwidth, Mbps, or complete connectivity services) to service providers, broadcasters, government agencies, and end users — examples include Intelsat, SES, Eutelsat, Viasat, Telesat, and Yahsat.
Satellite Phone
A handheld mobile phone that communicates directly with a satellite network rather than terrestrial cellular towers, providing voice, SMS, and limited data services globally — including remote wilderness, oceans, and conflict zones — using L-band frequencies from networks including Iridium, Inmarsat, and Globalstar.
Satellite Vertical: Agriculture
The application of Earth observation (multispectral crop monitoring, yield prediction), precision GNSS guidance (centimetre-accurate tractor steering), satellite IoT (weather stations, soil sensors), and satellite broadband (connectivity for remote farms) to optimise agricultural productivity and resource efficiency.
Satellite Vertical: Aviation
The use of satellite connectivity — In-Flight Connectivity (IFC), GNSS navigation, weather services, and ADS-B tracking — by the commercial aviation industry, spanning 45,000+ daily flights and connecting over 10,000 aircraft to a rapidly growing $6+ billion IFC market.
Satellite Vertical: Defence & Government
The use of satellite communications (MILSATCOM and commercial SATCOM), intelligence surveillance and reconnaissance (ISR) imagery, precision navigation, and missile warning services by military and government agencies — the largest single segment of the satellite industry by revenue and strategic importance.
Satellite Vertical: Energy
The use of satellite connectivity, Earth observation, and positioning services by the energy sector — covering offshore oil and gas platforms, onshore pipeline monitoring, renewable energy site assessment, and smart grid management — in environments where satellite is often the only practical communication medium.
Satellite Vertical: Humanitarian Aid
The use of satellite communication, Earth observation, and positioning by humanitarian organisations for disaster response (rapid mapping, logistics coordination), refugee camp connectivity, and crisis monitoring — including the Copernicus Emergency Management Service and NGO-deployed VSAT networks in conflict zones.
Satellite Vertical: Maritime
The use of satellite communication, Earth observation, and navigation services by the maritime industry — including commercial shipping, offshore oil and gas, fishing, and passenger vessels — for operational connectivity, crew welfare, vessel monitoring, safety compliance, and port logistics optimisation.
Satellite Vertical: Telecommunications
The use of satellite capacity by telecom operators for cellular backhaul in rural areas, DTH broadcasting infrastructure, submarine cable redundancy, and wholesale bandwidth for ISPs — the largest single revenue vertical in the commercial satellite industry, spanning both GEO transponder leasing and LEO managed services.
Satellite-as-a-Service (SataaS)
A commercial model where satellite capacity, connectivity, or data is consumed as a flexible, subscription-based service — priced per Mbps, per GB, or per device — rather than through traditional long-term capacity leases or satellite ownership, enabling customers to scale usage up or down without capital commitment.
SmallSat
A broad industry category for satellites below approximately 500 kg, encompassing CubeSats (1–10 kg), nanosats, microsats (10–100 kg), and minisats (100–500 kg), enabling lower-cost constellation deployment compared to traditional large GEO satellites.
Software-Defined Radio (SDR)
A radio system where functions traditionally implemented in hardware — filtering, amplification, modulation, demodulation — are instead performed by software running on programmable processors, enabling a single hardware platform to support multiple waveforms, frequency bands, and communication standards through software updates.
Software-Defined Satellite (SDS)
A satellite whose payload functions — beam patterns, frequency allocations, power distribution, and modulation schemes — can be reconfigured in-orbit via software upload, allowing operators to adapt to changing demand without launching a new spacecraft.
Solar Array
Panels of photovoltaic cells mounted on deployable wings that convert sunlight into electrical power for all satellite systems — the primary power source for virtually all Earth-orbiting spacecraft, sized to provide sufficient power through eclipse periods using onboard batteries.
Space Economy
All economic activities enabled by or conducted in space, including satellite manufacturing, launch services, satellite services (communications, Earth observation, navigation), downstream applications, and emerging sectors like in-space manufacturing and space tourism — valued at approximately $570 billion globally in 2023.
Space ISAC (Information Sharing and Analysis Center)
A non-profit membership organisation established in 2019 that facilitates cybersecurity threat intelligence sharing among satellite operators, launch providers, and ground system suppliers — enabling coordinated defence against common threats to space infrastructure.
Space Segment
The satellite or constellation of satellites that form the orbiting infrastructure of a space system, including all on-board hardware: the bus (power, propulsion, attitude control) and the payload (communications transponders, cameras, sensors).
Space Situational Awareness (SSA)
The knowledge and practice of tracking all objects in Earth orbit — from active satellites to debris fragments — predicting their trajectories, identifying conjunction risks, and informing collision avoidance decisions, carried out by national space surveillance networks, agencies like ESA, and a growing commercial sector.