Space Industry Glossary

An orbit around Earth with an altitude between 160 and 2,000 km. Most satellites, the ISS, and Starlink operate in LEO. Offers low latency for communications and high-resolution imaging but requires more satellites for global coverage.

An orbit between LEO and GEO, typically 2,000 to 35,786 km altitude. Used by GPS, GLONASS, and some communications constellations like O3b mPOWER. Balances coverage area with signal latency.

A circular orbit 35,786 km above Earth's equator where satellites match Earth's rotation, appearing stationary from the ground. Ideal for weather monitoring, TV broadcasting, and telecommunications. Three satellites can cover most of Earth.

An elliptical orbit used as an intermediate step to reach GEO. Satellites are launched to GTO then use onboard propulsion to circularize their orbit at geostationary altitude.

An elongated orbit with a low perigee and high apogee, providing extended coverage over specific regions. Molniya orbits are HEOs used by Russia for high-latitude communications coverage.

A polar orbit where the satellite passes over the same point at the same local solar time each day. Ideal for Earth observation satellites requiring consistent lighting conditions for imaging.

Orbits below 450 km altitude. Enables higher resolution imaging and lower latency but requires continuous propulsion to counteract atmospheric drag. Companies like Albedo operate in VLEO.

The region of space between Earth and the Moon, including Earth orbit, lunar orbit, and the space between. Increasingly important for lunar exploration and the Artemis program.

The change in velocity needed to perform a maneuver in space, measured in meters per second. A key metric for mission planning and propulsion system design.

The angle between a satellite's orbital plane and Earth's equatorial plane. A 0° inclination is equatorial; 90° is polar. Determines which latitudes a satellite can observe or service.

The propulsive maneuver that puts a spacecraft on a trajectory to the Moon. A critical burn that must be precisely timed and executed.

The point in an orbit where a satellite is farthest from Earth. In an elliptical orbit, velocity is slowest at apogee.

The point in an orbit where a satellite is closest to Earth. In an elliptical orbit, velocity is highest at perigee.

An orbit where the satellite moves opposite to Earth's rotation (west to east). Requires more energy to achieve than prograde orbits.

An orbit where the satellite moves in the same direction as Earth's rotation. Most launches use prograde orbits to take advantage of Earth's rotational velocity.

An orbit above GEO where retired geostationary satellites are moved to avoid interference with active satellites. Also called supersynchronous orbit.

An elliptical orbit used to transfer between two circular orbits using two engine burns. The most fuel-efficient transfer between coplanar circular orbits.

The time it takes for a satellite to complete one full orbit. LEO satellites orbit in about 90 minutes; GEO satellites take exactly 24 hours.

The cargo carried by a rocket, including satellites, spacecraft, or other equipment. Payload capacity is typically specified for different orbits (LEO, GTO, etc.).

The protective nose cone enclosing a rocket's payload during launch. Jettisoned once the rocket exits the atmosphere. SpaceX recovers and reuses fairings.

A section of a rocket with its own engines and propellant that separates after burnout. Multi-stage rockets shed mass to improve efficiency. First stages are increasingly being recovered and reused.

A landing profile where a rocket booster returns to land at or near its launch site. Used by SpaceX Falcon 9 for missions with lighter payloads, enabling rapid turnaround.

SpaceX's ocean-going landing platforms for recovering Falcon 9 and Falcon Heavy boosters. Named vessels like 'Of Course I Still Love You' and 'Just Read the Instructions.'

A measure of propulsion efficiency, expressed in seconds. Higher Isp means more thrust per unit of propellant. Chemical rockets achieve 250-450s; ion engines can exceed 3,000s.

A propellant combination using liquid methane and liquid oxygen. Used by SpaceX Raptor, Blue Origin BE-4, and Relativity engines. Can potentially be produced on Mars.

A high-performance propellant combination using liquid hydrogen and liquid oxygen. Highest specific impulse of chemical propellants but requires large tanks due to hydrogen's low density.

Propellants that ignite spontaneously on contact, requiring no ignition system. Used in spacecraft attitude control and lunar landers. Examples include hydrazine with nitrogen tetroxide.

Propulsion systems using electricity to accelerate propellant, including ion engines and Hall-effect thrusters. Very efficient (high Isp) but low thrust, ideal for satellite station-keeping and orbit raising.

An advanced rocket engine cycle where both propellants are fully gasified before combustion, maximizing efficiency. Used in SpaceX Raptor engines.

A highly refined kerosene used as rocket fuel. Denser than methane or hydrogen, making for smaller tanks. Used by Falcon 9, Electron, and many other rockets.

The oxidizer in most liquid-fueled rockets, stored at cryogenic temperatures (-183°C). Combined with various fuels including RP-1, methane, and hydrogen.

A rocket motor using solid propellant that cannot be throttled or shut down once ignited. Used for initial thrust on Space Shuttle, SLS, and Ariane rockets.

The ratio of thrust produced to the weight of the rocket. Must exceed 1.0 for liftoff. Higher TWR enables faster ascent and greater payload capacity.

The point during ascent when aerodynamic stress on the rocket is highest, typically 70-80 seconds after launch. Engines may be throttled down to reduce stress.

The moment when a rocket's first stage engines shut down, typically followed by stage separation. A critical mission milestone.

The shutdown of a rocket's second stage engine after achieving the desired orbit. May occur multiple times for complex mission profiles.

A pyrophoric mixture used to ignite rocket engines, particularly SpaceX's Merlin engines. Ignites spontaneously on contact with oxygen.

High-speed pumps that force propellants into the combustion chamber at high pressure. A complex and critical component of liquid rocket engines.

A cooling method where propellant flows through channels in the engine walls before combustion, absorbing heat and preheating the propellant.

A small propulsive stage that provides the final push to place a payload in its target orbit. Photon (Rocket Lab) and ESPA-based tugs serve as kick stages.

The main structural and functional platform of a satellite, providing power, propulsion, thermal control, and communications. Payloads are integrated onto the bus.

The mission-specific equipment on a satellite, such as cameras for imaging satellites, transponders for communications satellites, or scientific instruments.

A group of satellites working together as a system. Examples include Starlink (thousands of LEO satellites) and GPS (24+ MEO satellites). Enables global coverage and redundancy.

A standardized small satellite format using 10cm cubic units (1U = 10x10x10cm). Common sizes include 1U, 3U, 6U, and 12U. Reduced costs have democratized space access.

A ring-shaped adapter allowing multiple small satellites to ride as secondary payloads on larger launches. ESPA-class satellites typically mass 180-300 kg.

Satellites weighing under 500 kg. The smallsat revolution has driven costs down and capabilities up through miniaturization and mass production.

A launch where multiple customer payloads share a rocket, reducing costs. SpaceX Transporter missions have deployed hundreds of satellites per launch.

An imaging radar system that creates high-resolution images by combining data from multiple antenna positions. Can image through clouds and darkness. Used by Capella, Umbra, and others.

The use of satellites to monitor Earth's surface, atmosphere, and oceans. Includes optical imaging, radar, and multispectral/hyperspectral sensors.

The distance between pixel centers in a satellite image, measured on the ground. Lower GSD means higher resolution. Commercial leaders offer 30cm; some achieve sub-meter.

A device that receives, amplifies, and retransmits signals on different frequencies. Communications satellite capacity is often measured in transponders.

A satellite weighing between 1-10 kg. Many CubeSats fall into this category. Enabled by miniaturization of electronics and standardized deployment systems.

A satellite weighing between 10-100 kg. Capable of significant missions at lower cost than traditional satellites. Companies like Planet operate microsatellite fleets.

The system that determines and controls a satellite's orientation in space using sensors (star trackers, sun sensors) and actuators (reaction wheels, thrusters).

An optical device that determines a satellite's attitude by comparing observed star patterns to a catalog. Provides highly accurate orientation data.

A spinning wheel that changes a satellite's orientation through conservation of angular momentum. Does not consume propellant but requires periodic desaturation.

Photovoltaic panels that convert sunlight to electricity, providing power to satellites. Deployable arrays fold for launch and extend in orbit.

Imaging that captures data in multiple specific wavelength bands (typically 3-10). Used for vegetation analysis, land use mapping, and environmental monitoring.

Imaging that captures hundreds of narrow spectral bands across the electromagnetic spectrum. Enables detailed material identification and analysis.

How frequently a satellite can image the same location on Earth. LEO constellations can achieve sub-daily revisit; single satellites may take days or weeks.

Maneuvering a spacecraft close to another object for inspection, docking, or servicing. Critical for satellite servicing, debris removal, and space station operations.

Services performed on satellites in space, including refueling, repairs, upgrades, and life extension. Emerging market with companies like Starfish Space and Astroscale.

The capture and deorbiting of space debris. Companies like Astroscale are developing commercial debris removal capabilities to address the growing orbital debris problem.

The ability to detect, track, and characterize objects in space. Critical for collision avoidance, space security, and maintaining the space environment.

Knowledge of the space environment including natural phenomena, debris, and spacecraft. Foundation for safe space operations and conjunction assessment.

A spacecraft that moves payloads between orbits after launch. Companies like Impulse Space and Momentus provide last-mile delivery services in space.

The controlled or uncontrolled descent of a spacecraft from orbit, typically resulting in atmospheric reentry. Responsible operators deorbit satellites at end of life.

Small maneuvers to maintain a satellite's position against perturbations from gravity, solar radiation, and atmospheric drag. Consumes propellant that limits satellite life.

A payload integrated onto another organization's satellite, sharing the bus and launch costs. Enables faster, cheaper access to orbit for specialized instruments.

Analysis of potential close approaches or collisions between space objects. Operators receive conjunction warnings and may perform avoidance maneuvers.

Maneuvers performed to avoid potential collisions with debris or other satellites. Increasing traffic makes COLA operations more frequent and important.

Removing stored energy from a spacecraft at end of life to prevent explosions that create debris. Includes venting propellant and discharging batteries.

A protective spacecraft state triggered by anomalies, minimizing power consumption and pointing solar arrays at the sun while awaiting ground commands.

The process of increasing a satellite's altitude, often using electric propulsion over weeks or months to reach operational orbit from a lower deployment orbit.

Adjusting a satellite's position within its orbital plane to achieve desired spacing within a constellation. Critical for global coverage and revisit time.

Plans and actions to remove a satellite from operational orbit at end of life, either through controlled deorbit or raising to a graveyard orbit.

The transmission path from a satellite to a ground station or user terminal. Carries data, imagery, or video from space to Earth.

The transmission path from a ground station to a satellite. Used for commands, data uploads, and communications relay.

Radio frequencies between 26.5-40 GHz used for high-throughput satellite communications. Offers high bandwidth but is susceptible to rain fade.

Radio frequencies between 12-18 GHz used for satellite TV, data communications, and some radar. Good balance of bandwidth and weather resilience.

Radio frequencies between 40-75 GHz offering very high bandwidth for next-generation satellite communications. SpaceX has licenses for V-band Starlink operations.

Direct communication between satellites without going through ground stations. Starlink uses laser ISLs to route traffic globally with lower latency.

Using laser light for space communications instead of radio waves. Offers much higher data rates and security. Mynaric and others produce optical terminals.

Satellites using multiple spot beams and frequency reuse to achieve much higher capacity than traditional satellites. Viasat and SES operate HTS systems.

Satellite connectivity directly to standard smartphones without specialized equipment. AST SpaceMobile and Starlink are developing D2D services.

The time delay for signals to travel between points. LEO satellites offer ~20-40ms latency; GEO satellites have ~600ms round-trip delay.

Radio frequencies between 2-4 GHz used for telemetry, tracking, and command (TT&C) and some communications. Less affected by weather than higher bands.

Radio frequencies between 1-2 GHz used for GPS, Iridium, and maritime/aviation communications. Good propagation characteristics and weather resistance.

Radio frequencies between 4-8 GHz used for satellite communications and TV distribution. Being reallocated for 5G in many countries.

A focused satellite antenna beam covering a limited geographic area, allowing frequency reuse and higher throughput. HTS satellites use many spot beams.

A measure of transmitted signal strength combining transmitter power and antenna gain. Higher EIRP enables smaller receive antennas or longer range.

A figure of merit for receive systems combining antenna gain and system noise temperature. Higher G/T indicates better receive sensitivity.

The essential functions for monitoring satellite health (telemetry), determining position (tracking), and sending instructions (command).

Communication links between satellites, enabling data routing through space. Reduces dependence on ground stations and lowers latency for global communications.

A facility on Earth with antennas and equipment to communicate with satellites. May be dedicated or part of a shared network like AWS Ground Station or KSAT.

The facility where satellite operators monitor and control spacecraft, process commands, and manage mission activities. May be highly automated for large constellations.

Similar to MOC, the primary location for satellite command and control, health monitoring, and anomaly response.

Cloud-based ground station services allowing satellite operators to access a global network of antennas on-demand. Providers include AWS, Azure, Leaf Space, and KSAT.

A ground site with multiple satellite communication antennas, often serving different satellites or frequency bands.

A high-capacity ground station that connects a satellite constellation to terrestrial networks. Starlink gateways link the constellation to the internet backbone.

The equipment at an end-user location for satellite communication, such as Starlink's Dishy antenna or Iridium satellite phones.

An electronically steered antenna that can rapidly switch between satellites without mechanical movement. Used in Starlink terminals and many ground stations.

Compact satellite terminals typically with 0.6-2.4 meter dishes, used for business connectivity, maritime, and aviation applications.

A mechanically steered antenna that follows satellites across the sky. Required for LEO satellites that move quickly relative to the ground.

The U.S. satellite navigation system with 31 satellites in MEO. Provides position, navigation, and timing (PNT) services globally. Accuracy typically 3-5 meters.

The umbrella term for satellite navigation systems including GPS (US), GLONASS (Russia), Galileo (EU), BeiDou (China), and regional systems.

Russia's satellite navigation system with 24 satellites. Often used alongside GPS for improved accuracy and availability.

The European Union's satellite navigation system, designed for civil use with high accuracy. Fully operational since 2016.

China's satellite navigation system providing global coverage since 2020. Includes GEO, IGSO, and MEO satellites for enhanced Asia-Pacific coverage.

The three services provided by navigation satellites: determining location, enabling navigation, and providing precise time synchronization.

A technique that provides centimeter-level positioning accuracy using corrections from nearby reference stations. Used in surveying, agriculture, and autonomous vehicles.

A GNSS technique achieving decimeter to centimeter accuracy using precise satellite orbit and clock data without local reference stations.

Regional systems that improve GNSS accuracy and reliability. Examples include WAAS (US), EGNOS (Europe), and MSAS (Japan).

Emerging navigation services using LEO satellites for improved accuracy, faster acquisition, and resistance to jamming compared to traditional MEO GNSS.

NASA program contracting commercial companies to deliver payloads to the Moon. Participants include Intuitive Machines, Firefly Aerospace, and Astrobotic.

NASA contracts for cargo delivery to the ISS. SpaceX Dragon, Northrop Grumman Cygnus, and Sierra Space Dream Chaser provide CRS services.

NASA program enabling commercial transport of astronauts to the ISS. SpaceX Crew Dragon is the primary provider; Boeing Starliner is in development.

NASA's program to return humans to the Moon and establish sustainable presence. Includes SLS rocket, Orion spacecraft, Gateway station, and commercial landers.

U.S. DoD organization building the Proliferated Warfighter Space Architecture (PWSA), a mesh network of hundreds of LEO satellites for missile warning and military communications.

U.S. Space Force program procuring launch services for national security payloads. Phase 2 contracts went to ULA and SpaceX, with Blue Origin and Rocket Lab in Phase 3.

U.S. intelligence agency operating reconnaissance satellites. Increasingly partnering with commercial imagery and data providers.

SDA's distributed satellite network providing missile warning, tracking, and communications through hundreds of interconnected LEO satellites.

NASA's program for crewed lunar landers under Artemis. SpaceX Starship HLS won the initial contract; Blue Origin was selected for a second provider.

A planned small space station in lunar orbit serving as a staging point for lunar surface missions. International partners include ESA, JAXA, and CSA.

The largest structure in space, orbiting at ~400 km. A multinational collaboration since 1998. Planned for operation until 2030, with commercial stations as successors.

The NASA program that funded SpaceX and Orbital Sciences (now Northrop Grumman) to develop commercial cargo spacecraft. Precursor to CRS.

The modern commercial space industry characterized by private investment, rapid innovation, and cost reduction. Contrasted with traditional government-led 'Old Space' approach.

A shell company that raises funds through IPO to acquire a private company, taking it public. Many space companies including Virgin Galactic, Rocket Lab, and Planet went public via SPAC.

The total economic activity related to space, including satellite services, ground equipment, manufacturing, and government spending. Valued at over $400 billion annually.

U.S. regulations controlling export of defense articles and services, including many space technologies. Compliance is mandatory for U.S. space companies.

The main contractor responsible for delivering a complete system or mission, managing subcontractors. Lockheed Martin, Boeing, and Northrop Grumman are major primes.

Components or systems available commercially rather than custom-built. COTS parts reduce costs but may require qualification for space environments.

Components tested and certified to operate in the space environment, including radiation, thermal extremes, and vacuum. More expensive than commercial parts.

Electronics designed to withstand space radiation that can cause errors or damage. Essential for satellites in high-radiation orbits or long-duration missions.

A 1-9 scale measuring technology maturity from basic research (TRL 1) to flight-proven systems (TRL 9). Used by NASA and space industry for development planning.

A 1-10 scale measuring manufacturing maturity and production capability. Higher levels indicate readiness for full-rate production.

U.S. government program providing R&D funding to small businesses. Many space startups receive SBIR grants for technology development.

A trajectory that reaches space (above 100 km) but does not achieve orbital velocity. Used for space tourism (Blue Origin, Virgin Galactic) and research.

The speed required to maintain orbit around Earth, approximately 7.8 km/s in LEO. Below this speed, objects fall back to Earth.

A large customer whose guaranteed business enables a startup to secure funding and scale. NASA and DoD often serve as anchor customers for space companies.

The total value of contracts signed but not yet completed. A key metric for space companies indicating future revenue.

Two zones of high-energy particles trapped by Earth's magnetic field. Satellites must be designed to survive or avoid these radiation-intense regions.

Non-functional objects in orbit including defunct satellites, spent rocket stages, and collision fragments. Over 36,000 tracked objects; millions of smaller pieces.

A theoretical scenario where collisions generate debris faster than it naturally decays, potentially making some orbital regions unusable.

The condition of apparent weightlessness in orbit, actually a state of continuous freefall. Enables unique manufacturing and research opportunities.

The release of gases from materials in vacuum. Can contaminate optics and solar panels. Space-qualified materials undergo outgassing tests.

The extreme temperature swings satellites experience moving between sunlight and shadow, from +150°C to -150°C. Requires careful thermal design.

A bit flip in electronics caused by radiation, potentially corrupting data or commands. Mitigation includes error-correcting codes and redundancy.

A potentially destructive condition in electronics caused by radiation, creating a high-current path that can damage components if not quickly interrupted.

Small particles that can damage spacecraft. ISS has shields; satellites rely on design margins and collision avoidance.

Eruptions of radiation and particles from the Sun that can damage electronics, degrade solar panels, and affect communications. Operators monitor space weather.

The deceleration of LEO satellites due to residual atmosphere. Varies with altitude and solar activity. Requires station-keeping propulsion or leads to reentry.

A spacecraft designed to carry humans, such as SpaceX Crew Dragon, Boeing Starliner, or Orion. Includes life support and crew safety systems.

An uncrewed spacecraft for delivering supplies to space stations, such as Dragon, Cygnus, or Progress. Some are recoverable; others burn up on reentry.

A spacecraft designed to land on a planetary body. Examples include Intuitive Machines Nova-C lunar lander and SpaceX Starship HLS.

A mobile vehicle for exploring planetary surfaces. NASA's Perseverance on Mars and VIPER (planned for Moon) are examples.

A habitable structure in orbit for long-duration human presence. ISS is current; Axiom, Vast, and Starlab are developing commercial successors.

A propulsive vehicle that moves satellites between orbits. Companies like D-Orbit, Launcher, and Momentus offer tug services.

A rocket design reaching orbit with one stage and no jettisoned hardware. Theoretically attractive but physically challenging; no operational SSTO exists.

A vehicle that combines rocket propulsion with aircraft-like landing. Examples include Space Shuttle (retired), Dream Chaser (cargo), and X-37B (military).

A conical or spherical spacecraft using ablative heat shields for reentry. Dragon, Orion, and Starliner are capsule designs.

The section of a spacecraft providing propulsion, power, and consumables. Often discarded before reentry. ESA provides Orion's service module.

A space mission carrying human passengers. Requires extensive safety systems and life support. Current crewed vehicles include Dragon, Soyuz, and Shenzhou.

Space missions without human passengers. Includes satellites, planetary probes, and cargo vehicles. Lower risk tolerance than crewed missions.

The most common launch mission type, placing satellites in low Earth orbit for communications, imaging, or other services.

Launching a satellite to geostationary transfer orbit for subsequent circularization to GEO. Requires more energy than LEO missions.

Missions beyond Earth orbit to other planets, moons, or asteroids. Requires precise trajectory planning and often years of travel time.

Missions that collect material from other bodies and return it to Earth for analysis. Examples include Hayabusa2 (asteroid) and Mars Sample Return (planned).

A mission that passes close to a target body without orbiting or landing, using the encounter for science and sometimes gravity assist.

Using a planet's gravity to change a spacecraft's trajectory and speed. Enables missions to outer planets that would otherwise require unfeasible propellant.

Cargo delivery to space stations. Regular missions bring food, equipment, experiments, and crew supplies to ISS.

Missions primarily designed to test new technologies in space. Often precede operational deployment. NASA and DARPA fund many tech demos.

A controlled environment with low levels of particulates and contaminants. Satellites are assembled in cleanrooms to prevent contamination.

Testing spacecraft in chambers that simulate the vacuum and temperature extremes of space. Critical for validating designs before launch.

Subjecting spacecraft to vibration profiles matching launch loads. Identifies structural weaknesses before flight.

The process of assembling spacecraft components, integrating subsystems, and testing the complete satellite before launch.

The final phase of spacecraft manufacturing where components are combined and verified to work together as a system.

Using 3D printing to produce spacecraft components. Enables complex geometries, reduced lead times, and in-space manufacturing potential.

Manufacturing satellites in large quantities using assembly lines and automation. OneWeb, Starlink, and Planet use mass production for constellations.

A spacecraft built and tested to destruction to verify design margins before building flight units. Undergoes more extreme testing than flight hardware.

A fully qualified backup spacecraft ready for launch if the primary fails. Common for high-value or time-critical missions.

An approach where the first unit undergoes qualification testing at reduced levels and then flies. Reduces cost but increases risk.

Using resources found at a destination rather than bringing them from Earth. Water ice on the Moon could produce propellant and drinking water.

Transferring propellant between spacecraft in orbit to extend missions. Orbit Fab is developing fuel depots; NASA's Starship HLS requires orbital refueling.

Extracting resources from asteroids or the Moon. Water, metals, and rare elements could support in-space industry. Still largely developmental.

The transition of low Earth orbit activities from government-dominated to commercial. Commercial space stations, tourism, and manufacturing are emerging.

Commercial human spaceflight for recreation. Suborbital (Virgin Galactic, Blue Origin) and orbital (Axiom, SpaceX) experiences are available.

Producing materials or products that benefit from microgravity conditions. Applications include fiber optics, pharmaceuticals, and metal alloys.

Using satellites or space infrastructure for marketing. Controversial proposals include orbital billboards and satellite formations visible from Earth.

Business model where satellite operators sell insights and analytics rather than raw data. Adds value through processing and interpretation.