Satellites can be classified in various ways depending on their purpose, orbit, and design. This article reviews the common classifications.
- Communication satellites: Used for transmitting television, telephone, and internet signals.
- Earth observation satellites: Used for monitoring weather, environmental changes, natural resources, and land use.
- Navigation satellites: Used for providing location and timing information, such as GPS, GLONASS, and Galileo systems.
- Scientific satellites: Used for scientific research in fields like astronomy, space physics, and Earth science.
- Military satellites: Used for reconnaissance, surveillance, and communication purposes by defense forces.
- Space exploration satellites: Used to study other celestial bodies, like the Mars rovers, lunar orbiters, and interplanetary probes.
- Low Earth Orbit (LEO): Satellites orbiting at an altitude of approximately 160-2,000 km above the Earth's surface.
- Medium Earth Orbit (MEO): Satellites orbiting at an altitude of approximately 2,000-35,786 km.
- Geostationary Earth Orbit (GEO): Satellites orbiting at an altitude of approximately 35,786 km, remaining in a fixed position relative to the Earth's surface.
- Highly Elliptical Orbit (HEO): Satellites with orbits that have a high eccentricity, resulting in a large difference between their closest and farthest points from Earth.
- Sun-synchronous Orbit (SSO): Satellites orbiting in a way that allows them to pass over the same point on Earth's surface at the same local solar time, enabling consistent lighting conditions for imaging and observation.
Mass and Design Configuration
There are a variety of ways of classifying a satellite by mass. Examples are given below.
- The CubeSat standard defines a set of specifications for small satellites with a standard size, shape and mass.
- The EELV Secondary Payload Adapter (ESPA) is a multi-payload adapter that can be used to launch multiple small satellites on a single rocket. Satellites that use the ESPA class adapter are typically between 50 kg (110 lbs) and 500 kg (1,102 lbs) in mass. The ESPA class is used by the U.S. Air Force for some of their space missions.
Radio Frequencies Used
|Frequency Band||Frequency Range||Applications|
|L-band||1 – 2 GHz||GPS navigation, satellite phones|
|S-band||2 – 4 GHz||Satellite communication, remote sensing, radar|
|C-band||4 – 8 GHz||TV and radio broadcasting, military communication|
|X-band||8 – 12 GHz||Satellite communication, radar, remote sensing|
|Ku-band||12 – 18 GHz||DTH satellite TV broadcasting, broadband internet services|
|Ka-band||18 – 40 GHz||Broadband internet services, high-throughput satellites|
- Short-term satellites: Satellites with a lifespan of a few months to a couple of years, often used for technology demonstrations, research, or short-term missions.
- Medium-term satellites: Satellites with a lifespan of several years, commonly used for communication, Earth observation, and navigation purposes.
- Long-term satellites: Satellites with a lifespan of more than a decade, typically used for deep-space missions or geostationary communication satellites.
- Chemical propulsion satellites: Satellites that use chemical propellants for maneuvering, orbit adjustments, and deorbiting.
- Electric propulsion satellites: Satellites that use electric propulsion systems, such as Hall-effect thrusters, ion thrusters, or plasma thrusters, to provide thrust with higher efficiency than chemical propulsion systems.
- Hybrid propulsion satellites: Satellites that use a combination of chemical and electric propulsion systems for different mission phases or purposes.
Control and Stabilization
- Spin-stabilized satellites: Satellites that maintain stability by spinning around their primary axis, much like a gyroscope.
- Three-axis stabilized satellites: Satellites that maintain stability and precise orientation using reaction wheels, gyroscopes, or thrusters.
- Solar-powered satellites: Satellites that use solar panels to convert sunlight into electrical power, typically used for satellites in Earth orbit.
- Nuclear-powered satellites: Satellites that use nuclear reactors or radioisotope thermoelectric generators (RTGs) as a power source, mainly used for deep-space missions or long-duration missions where solar power is insufficient.
- Battery-powered satellites: Satellites that rely on batteries for their power supply, generally used for small or short-duration missions.
Ownership and Operation
- Government-owned satellites: Satellites owned and operated by national governments or their agencies, typically for scientific, military, or public-service purposes.
- Commercial satellites: Satellites owned and operated by private companies, used for a variety of applications such as communication
Launch Vehicle and Deployment
- Single satellite launches: Satellites launched individually by a dedicated launch vehicle.
- Multi-satellite launches: Satellites launched in groups on a single launch vehicle, often used for deploying constellations or for cost-effective launches.
- Piggyback satellites: Smaller satellites launched as secondary payloads alongside a primary satellite or mission.
- Single-satellite systems: Satellites operating independently to fulfill their mission objectives.
- Satellite constellations: Groups of satellites working together in a coordinated manner to provide coverage or services, such as GPS, Starlink, or OneWeb.
- Satellite swarms: Large groups of small satellites designed to operate collectively, sharing data and resources, and performing coordinated tasks.
- Passive payload satellites: Satellites carrying passive instruments, such as reflectors or antennas, which do not require active power or data processing.
- Active payload satellites: Satellites carrying active instruments, such as cameras, radars, or spectrometers, which require power and processing capabilities to perform their tasks.
Reusability and Servicing
- Non-reusable satellites: Satellites designed for single-use, with no provisions for refurbishment or reuse.
- Reusable satellites: Satellites designed with the capability to be refurbished and reused for multiple missions, potentially reducing costs and environmental impacts.
- Servicing-compatible satellites: Satellites designed with features that allow in-orbit servicing, repair, or refueling by specialized servicing spacecraft or robotic systems.
These classification types demonstrate the diversity of satellite missions, designs, and applications. As satellite technology continues to evolve, new classification types may emerge to describe new capabilities, technologies, and mission objectives. It's important to keep in mind that many satellites can fit into multiple categories, and their specific classification depends on the context in which they are being considered. Additionally, the rapid advancement of satellite technology is leading to the development of innovative solutions that challenge traditional classification schemes, such as on-orbit assembly, satellite manufacturing in space, and the use of artificial intelligence for satellite operations.