Understanding Low Earth Orbit: Where the Action Is
If you've watched a SpaceX launch or seen Starlink satellites in the night sky, you've been watching activity in Low Earth Orbit. It's the most economically valuable and most crowded region of space. This explainer covers what LEO actually is, why it matters, and what the next decade is going to look like up there.
What counts as "low"?
Low Earth Orbit is conventionally defined as altitudes between roughly 160 km and 2,000 km above Earth's surface. The lower bound is set by atmospheric drag — below ~160 km, even thin atmospheric molecules slow down satellites fast enough to pull them back to burn up within days. The upper bound is fuzzier, but generally anything below 2,000 km is "LEO," and above that you start talking about Medium Earth Orbit (MEO, used by GPS) and Geostationary Orbit (GEO, at ~35,786 km).
For practical purposes, most LEO activity today happens between 400 km and 600 km altitude. The International Space Station sits at about 408 km. Most Starlink satellites operate around 550 km. Earth observation satellites cluster in the 500–800 km range.
Why LEO is special
Three reasons make LEO the most interesting neighborhood in space:
1. It's close. A 400 km altitude means a round-trip light-speed signal from Earth's surface to a LEO satellite and back takes about 3 milliseconds. Compare that to GEO at 35,786 km, where the same signal takes about 240 ms — a delay that makes real-time voice calls awkward. This is why Starlink (LEO) is competitive with traditional broadband in a way that older satellite internet (GEO) never was.
2. You can get there cheaply. Reaching LEO requires a delta-v (change in velocity) of roughly 9.4 km/s. Reaching GEO requires about 13.5 km/s, including the upper-stage burns to circularize. The difference is enormous in fuel cost and rocket size. This is why virtually every commercial constellation targets LEO.
3. The physics are friendly. In LEO, you're still under most of Earth's protective magnetic field. You're not in the worst of the Van Allen radiation belts. Solar radiation is real but manageable with standard spacecraft-grade components.
What's actually in LEO right now?
As of mid-2026, the tracked population in LEO is roughly:
- ~7,500 active satellites (about 60% are Starlink)
- ~2,500 defunct satellites still orbiting
- ~34,000 trackable debris objects larger than 10 cm
- Millions of smaller fragments that can't be reliably tracked
The math on debris is what keeps orbital debris researchers up at night. Every collision creates more fragments, which can cause more collisions, in a cascade called the Kessler Syndrome. The most-cited worst case is a chain reaction that makes certain LEO altitudes unusable for decades.
The orbital mechanics that matter
A few concepts come up constantly when reading about LEO:
Altitude vs. orbital period. A satellite's altitude determines its orbital period (the time to complete one orbit). The ISS at 408 km completes an orbit every 93 minutes — about 16 orbits per day. Starlink at 550 km takes about 96 minutes per orbit. Higher orbits = longer periods.
Inclination. The angle of the orbit relative to Earth's equator. ISS is at 51.6° inclination (chosen partly for Russian launch geometry). Starlink has multiple orbital shells at different inclinations — the current ones are 53°, 70°, and 97.6° (polar).
Right ascension of the ascending node (RAAN). Where the orbit crosses the equator going north. This matters because it determines what ground stations can see the satellite.
Argument of perigee. If the orbit is elliptical, where the lowest point is. Most LEO satellites fly circular orbits, so this is often irrelevant.
Eccentricity. How "stretched" the orbit is. 0 = perfect circle, 0.5 = noticeably elliptical. Most Starlinks fly circular or near-circular.
The big challenges coming
Three problems will define LEO in the next ten years:
1. Debris mitigation. The FCC and ITU are starting to require 5-year post-mission disposal for LEO satellites. That means deorbit within 5 years of mission end — usually via controlled re-entry or natural decay. Satellites launched today must plan for this from day one.
2. Spectrum coordination. With tens of thousands of satellites beaming internet down to Earth, the radio spectrum is getting crowded. Coordination between operators (Starlink, Kuiper, Guowang, Qianfan, and others) is increasingly a regulatory and diplomatic challenge.
3. Traffic management. The US Space Force tracks everything in orbit. As traffic grows, automated collision avoidance becomes essential. Current systems rely on manual review of conjunction warnings — that won't scale to 100,000+ satellites.
What's coming next
Expect to see, in rough order:
- More Starlink shells (SpaceX is filling out global coverage and adding direct-to-cell)
- Kuiper going live (Amazon's constellation, launching through 2027)
- Chinese mega-constellations (Guowang and Qianfan, hundreds of satellites each)
- In-orbit servicing (satellites refueling or repairing other satellites in LEO)
- Commercial space stations (replacing ISS, planned for 2028-2030)
- Active debris removal (a small industry, but the first contracts are being signed)
LEO is going to get a lot busier. The physics hasn't changed, but the engineering and the regulatory environment are evolving fast.