Satellite Constellations Explained: From GPS to Starlink

A satellite constellation is a group of satellites working together as a coordinated system to provide continuous coverage of the Earth or a specific region. While a single satellite in low Earth orbit can only "see" a small portion of the planet at any given time, a constellation of dozens, hundreds, or thousands of satellites in carefully chosen orbits can provide persistent global coverage. This concept has revolutionized navigation, communications, Earth observation, and defense, and it is reshaping the space economy in 2026.

How Constellations Work

The fundamental challenge of satellite coverage is geometry. A satellite in LEO (200-2,000 km altitude) orbits the Earth every 90-120 minutes and can see a footprint of roughly 1,000-3,000 km in diameter depending on altitude and the service's minimum elevation angle. For any given point on the ground, the satellite is overhead for only 5-15 minutes per pass.

A constellation solves this by distributing satellites across multiple orbital planes: imagine a set of rings tilted at different angles around the Earth, with satellites evenly spaced along each ring. As one satellite passes out of view, the next one in the constellation rises above the horizon to take over. The key design parameters are:

• Number of planes: More planes provide faster revisit times and better coverage at different latitudes
• Satellites per plane: More satellites per plane reduce gaps in coverage along each orbital track
• Altitude: Higher orbits provide larger footprints (requiring fewer satellites) but with higher latency and greater radiation exposure
• Inclination: The tilt of the orbital plane relative to the equator determines which latitudes receive coverage. Polar orbits (90-degree inclination) cover the entire Earth; equatorial orbits (0-degree) only cover tropical regions

Navigation Constellations

GPS (United States)

The original satellite constellation that changed the world. The Global Positioning System consists of 31 operational satellites in Medium Earth Orbit (MEO) at approximately 20,200 km altitude, distributed across 6 orbital planes. Each satellite broadcasts precise timing signals; a GPS receiver on the ground measures the time delay from at least 4 satellites to calculate its position to within a few meters. GPS was developed by the U.S. Department of Defense starting in the 1970s and opened to civilian use in 1983. Today, GPS underpins everything from smartphone navigation to precision agriculture to financial transaction timestamping.

GLONASS (Russia)

Russia's Global Navigation Satellite System operates 24 satellites in MEO at 19,130 km across 3 orbital planes. GLONASS uses frequency-division multiple access (FDMA), distinguishing it from GPS's code-division approach. Most modern smartphones use both GPS and GLONASS for improved accuracy.

Galileo (European Union)

Europe's independent navigation system has 28 satellites in MEO at 23,222 km across 3 orbital planes. Galileo offers a free civilian service comparable to GPS and a commercial encrypted service with centimeter-level accuracy. Full operational capability was declared in 2024.

BeiDou (China)

China's BeiDou Navigation Satellite System is the newest global constellation, completed in 2020 with 35 satellites in a hybrid MEO/GEO/IGSO architecture. BeiDou provides regional messaging capability in addition to global navigation, a unique feature among GNSS systems.

Broadband Internet Constellations

Starlink (SpaceX)

The constellation that launched the mega-constellation era. As of early 2026, SpaceX has deployed over 6,500 Starlink satellites in LEO at 540-570 km altitude, with plans to eventually operate up to 42,000. Starlink provides broadband internet at speeds of 50-250 Mbps with latency of 20-40ms, comparable to cable internet and dramatically better than legacy GEO satellite internet. The constellation uses V2 Mini satellites (each about 800 kg) with inter-satellite laser links that allow data to route through space without touching the ground. Starlink serves over 4 million subscribers across 70+ countries.

OneWeb (Eutelsat OneWeb)

Following a bankruptcy and rescue by the UK government and Bharti Global in 2020, OneWeb completed its first-generation constellation of 648 satellites at 1,200 km altitude. OneWeb targets enterprise and government customers rather than consumers, with a focus on backhaul connectivity, maritime, aviation, and bridging the digital divide in underserved regions. The merger with Eutelsat created a combined GEO/LEO operator with a comprehensive product portfolio.

Project Kuiper (now Amazon Leo) (Amazon)

Amazon's constellation plans call for 3,236 satellites in LEO at 590-630 km. After launching prototype satellites in late 2023, Amazon has been ramping production at its Kirkland, WA facility with a goal of deploying half the constellation by mid-2026. Kuiper will compete directly with Starlink for consumer and enterprise broadband, leveraging Amazon's existing cloud infrastructure (AWS) and consumer hardware expertise.

Earth Observation Constellations

Planet Labs

Planet operates the largest Earth observation constellation with over 200 SuperDove satellites in sun-synchronous orbit at ~475 km. The fleet images the entire land surface of Earth every day at 3-5 meter resolution. Planet also operates a smaller fleet of SkySat satellites providing 50cm resolution imagery. The daily global scan enables change detection for agriculture, forestry, disaster response, and supply chain monitoring.

BlackSky

BlackSky's constellation of 18 satellites provides high-revisit electro-optical imagery at ~1 meter resolution. Unlike Planet's systematic global mapping, BlackSky focuses on rapid tasking: customers can request an image of a specific location and receive it within hours. The company pairs satellite imagery with AI analytics and social media monitoring.

Spire Global

Spire operates 100+ CubeSats carrying radio occultation sensors for weather data, AIS receivers for maritime vessel tracking, and GNSS reflectometry instruments for ocean surface measurements. Rather than capturing images, Spire's satellites measure physical phenomena and sell the resulting data to weather services, shipping companies, and governments.

Military and Defense Constellations

Space Development Agency (SDA) Transport Layer

The U.S. Space Development Agency is building the Proliferated Warfighter Space Architecture (PWSA), a LEO constellation of hundreds of military satellites for missile tracking, data transport, and communications. Tranche 0 (28 satellites) launched in 2024. Tranche 1 (126 satellites) is deploying in 2025-2026. The constellation includes both "transport" satellites for secure military data relay and "tracking" satellites with infrared sensors for missile warning. Companies including Lockheed Martin, Northrop Grumman, L3Harris, and York Space Systems are building the spacecraft.

Golden Dome

The U.S. missile defense program will deploy a proliferated LEO constellation for tracking hypersonic weapons. Details remain classified, but the architecture will complement SDA's tracking layer with additional sensor capabilities. The program represents the largest planned military constellation investment since GPS.

The Economics of Constellations

Deploying a satellite constellation is a massive capital investment with unique financial characteristics:

• Upfront capital: Building and launching a constellation requires billions before generating revenue. Starlink cost SpaceX an estimated $10B+ before reaching profitability. OneWeb spent $3.4B before its bankruptcy.
• Replacement cycle: LEO satellites have 5-7 year lifespans due to atmospheric drag. Constellation operators must continuously launch replacement satellites, creating ongoing capital expenditure. Starlink launches roughly 20-40 satellites per week to maintain and grow its fleet.
• Economies of scale: The per-satellite cost drops dramatically with volume production. SpaceX's V2 Mini satellites are estimated to cost under $500K each, orders of magnitude cheaper than traditional GEO satellites. This is only possible at thousands-unit production volumes.
• Revenue per satellite: A constellation's financial viability depends on generating enough revenue per satellite to cover manufacturing, launch, operations, and replacement costs. Starlink's 4 million subscribers across 6,500 satellites translates to roughly 600 subscribers per satellite.

The Future of Constellations

The next decade will see constellation deployment accelerate across multiple domains. Direct-to-device constellations (AST SpaceMobile, Lynk Global) will connect smartphones directly from orbit. Optical inter-satellite links will create a mesh network in space with lower latency than terrestrial fiber for long-distance routes. And constellations will expand beyond Earth: NASA's LunaNet concept envisions a constellation around the Moon providing navigation and communications for Artemis-era lunar operations.

Track every constellation (current, planned, and in-development) with the SpaceNexus Constellation Tracker. See satellite counts, orbital parameters, operator data, and deployment progress in real time.

Explore the Constellation Tracker on SpaceNexus