What is MEO? Medium Earth Orbit and Its Uses

Medium Earth Orbit (MEO) is the region of space between approximately 2,000 kilometers and 35,786 kilometers above Earth's surface, above low Earth orbit (LEO) and below geostationary orbit (GEO). It is one of the most strategically important orbital regimes in the space economy, home to the navigation constellations that underpin modern civilization and a growing number of broadband communications satellites designed to bridge the gap between LEO's low latency and GEO's wide coverage.

Defining MEO: Where It Sits and Why It Matters

The boundaries of MEO are defined by what lies above and below it. LEO extends from roughly 160 km to 2,000 km altitude. GEO sits at exactly 35,786 km, where a satellite's orbital period matches Earth's rotation. Everything in between is MEO, a vast expanse of orbital space with a range of useful properties.

Satellites in MEO typically orbit at altitudes between 5,000 km and 20,200 km. At these altitudes, orbital periods range from about 2 hours to 12 hours. The higher altitude compared to LEO means each satellite has a larger footprint: it can see more of Earth's surface at any given time, while still maintaining significantly lower latency than GEO satellites.

This middle-ground positioning is what makes MEO strategically valuable. A MEO constellation needs fewer satellites than a LEO constellation to achieve global coverage, but delivers much lower signal delay than GEO systems. For applications where both coverage efficiency and latency matter, MEO is often the optimal choice.

Navigation Constellations: MEO's Primary Residents

The most critical MEO satellites are the global navigation satellite systems (GNSS) that billions of people rely on daily:

• GPS (United States): 31 operational satellites at approximately 20,200 km altitude in six orbital planes. GPS III satellites are the current generation, offering improved accuracy and anti-jamming capabilities.
• Galileo (European Union): 28 satellites at 23,222 km altitude. Galileo offers the highest civilian accuracy of any GNSS, with its High Accuracy Service delivering centimeter-level positioning.
• GLONASS (Russia): 24 satellites at 19,130 km altitude. Russia's navigation system has been operational since 1993 and is undergoing modernization with GLONASS-K2 satellites.
• BeiDou (China): 30 MEO satellites (plus additional GEO and IGSO satellites) at 21,528 km altitude. BeiDou achieved global coverage in 2020 and is China's answer to GPS dependency.

These four constellations collectively represent over 110 MEO satellites, and their signals are so deeply integrated into modern infrastructure (from aviation to banking to agriculture) that their disruption would have cascading effects across the global economy. The value of GPS alone to the U.S. economy has been estimated at over $1.4 trillion per year.

MEO Broadband: The O3b Revolution

While navigation dominates MEO historically, the regime is increasingly attractive for broadband communications. The pioneer in this space is SES's O3b constellation, originally conceived as "Other 3 Billion", a reference to connecting the three billion people without reliable internet access.

The original O3b system launched 20 satellites into MEO at approximately 8,062 km altitude, providing broadband connectivity to maritime, aviation, government, and telecom customers. The system's MEO altitude delivers latency of approximately 150 milliseconds round-trip, roughly half of GEO and adequate for most real-time applications including video conferencing and cloud computing.

SES has since deployed O3b mPOWER, a next-generation MEO constellation with software-defined, multi-orbit capabilities. The mPOWER system features high-throughput satellites with thousands of electronically steerable beams, delivering terabits of capacity with the flexibility to allocate bandwidth dynamically based on demand. O3b mPOWER represents the most advanced commercial MEO communications system in operation.

Advantages of MEO Over LEO and GEO

MEO offers a distinct set of advantages compared to the more commonly discussed orbital regimes:

• Fewer satellites for global coverage: Because each MEO satellite sees a larger portion of Earth than a LEO satellite, a MEO constellation can achieve global coverage with 20-50 satellites rather than the hundreds or thousands required in LEO. This reduces manufacturing, launch, and operational costs.
• Lower latency than GEO: At 8,000-20,000 km altitude, MEO satellites deliver round-trip latencies of 100-250 ms, compared to 600+ ms for GEO. This makes MEO suitable for latency-sensitive applications that GEO cannot serve well.
• Longer orbital lifespan: MEO satellites experience significantly less atmospheric drag than LEO satellites, enabling operational lifespans of 15-20 years without station-keeping fuel concerns. LEO satellites, particularly in lower orbits, may last only 5-7 years.
• Reduced space debris risk: The MEO environment is far less congested than LEO, where over 10,000 active satellites and millions of debris fragments create an increasingly challenging environment.
• More stable radiation environment: While MEO does pass through the Van Allen radiation belts, modern satellite hardening techniques have made this manageable. The trade-off is a more predictable radiation environment than the variable conditions in LEO.

Challenges and Trade-offs

MEO is not without its challenges. The Van Allen radiation belts, zones of high-energy particles trapped by Earth's magnetic field, extend through much of the MEO region, particularly between 1,000 km and 60,000 km altitude. Satellites must be radiation-hardened, adding cost and weight. The higher altitude also means greater signal path loss compared to LEO, requiring more powerful transmitters or larger antennas on the ground.

Additionally, MEO orbits are subject to gravitational perturbations from the Sun and Moon that require periodic station-keeping maneuvers. And because MEO is between LEO and GEO, it can potentially interact with both orbital regimes during conjunction events, complicating space traffic management.

The Future of MEO

As LEO becomes increasingly congested with mega-constellations and GEO approaches its capacity limits at prime orbital slots, MEO is attracting renewed attention from both commercial and government operators. The U.S. Space Force is exploring MEO architectures for resilient communications and missile warning, and commercial operators are evaluating MEO for applications ranging from IoT connectivity to scientific research.

MEO may not generate the headlines that Starlink or geostationary broadcast satellites do, but it is the backbone of global navigation, a growing force in broadband, and an increasingly strategic orbital regime for the next decade of space development.

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