Satellite Constellations: Existing And Emerging Swarms

With thousands of satellite constellations in space presently, our planet will witness even more launches in the upcoming years. The existing and new satellite constellations serve many spheres being useful in the internet of things, telecommunications, navigation, weather monitoring, Earth and space observation, to mention a few.

Typically revolving on the low Earth orbit, satellite constellations provide the required data with quick signal transmitting time (downlink and uplink), valuable when immediate response is critical. Compared to single large satellites, swarms of small units (up to 500 kg) are cheaper and faster to deploy.

What Is A Satellite Constellation?

A satellite constellation (or swarm) is a network of identical or similar-type artificial units with the same purpose and shared control. Such groups communicate to worldwide-located ground stations and sometimes are inter-connected. They work as a system and are designed to complement each other. First, satellites in swarms revolve on several, usually similar orbits (orbital planes) ensuring uninterrupted or nearly uninterrupted global coverage. Second, individual constellation units can technically capture a vaster territory compared to a single remote sensing medium.

GEO vs. MEO vs. LEO Satellite Constellations

Depending on the orbital altitude ^{Dr. Naser Al-Falahy. Advanced Communication Systems. University of Anbar, College of engineering. pp: 7-12.}, there are three different types of satellite constellations: GEO, MEO, and LEO. Each type has its specifics and is important for a particular purpose, so let’s consider how these three compare.

GEO Satellite Constellations

GEO stands for a geostationary (or geosynchronous equatorial) orbit that hosts hundreds of satellites nowadays. Geostationary swarms derived their name from their Earth-rotation mode: they synchronize with our planet’s movement, thus hovering all the time over the same point. It happens because GEO swarms fly over the equator, and each rotation takes 24 hours. GEO is a typical orbit for weather satellite constellations. Others broadcast TV and provide low-speed communication services.

Thanks to the altitude of 36,000 km, an individual GEO satellite can capture 40% of the Earth’s surface. Thus, a group of three units 120 angular degrees apart is enough to keep an eye on the whole world.

MEO Satellite Constellations

MEO is an acronym for medium Earth (or mid-Earth) swarms operating at the altitude of 5,000 to 20,000 km and traditionally serving for navigation purposes. MEO constellations also provide high-bandwidth connectivity in locations where terrestrial infrastructure is poor or not feasible. This particularly refers to maritime and aerospace industries, offshore platforms, and rescue team operations in remote areas.

LEO Satellite Constellations

LEO swarms make the densest space population, operating at an altitude of 500 to 1,200 km. The derived data is widely used by governmental bodies, as well as commercial and non-commercial organizations. Low Earth orbit satellite constellations primarily support research, telecommunication, and Earth Observation needs of environmental monitoring, disaster response, forestry, and agri-sector.

Such swarms may have circular or elliptical orbits ^{Orbits Necessary for Remote Sensing. Texas Space Grant Consortium.}. Circular orbits are at the same altitude, while elliptical orbits contain the apogee (the highest point) and the perigee (the lowest one). Swarms with circular orbits revolve around our planet within 1.5 to several hours and typically fly nearly above the geographic poles. As for elliptical orbits, they are passed slower at the apogee and faster at the perigee points.

Why Are Satellite Swarms Important?

The first satellite constellations were launched in the 1960s, and many were deployed from the 1990s up to date. Swarms perform a number of tasks from fiber-like internet connectivity to multi-purpose Earth monitoring, obtaining quality imagery for subsequent AI-powered data procession by analytical platforms. Remote sensing data users particularly rejoice when they can buy services at affordable prices to get clear answers to their questions, and EOSDA is able to provide cost-effective and reliable solutions.