Satellites and Orbits, Explained Simply

What an orbit really is

An orbit is a fall that never ends. Imagine standing on an impossibly tall mountain and throwing a ball straight out, level with the ground. Throw gently and it curves down nearby; throw harder and it lands further away.

Now imagine throwing it so fast that, as it falls, the ground curves away beneath it just as quickly. The ball keeps falling but keeps missing Earth. Near Earth that takes a sideways speed of about 7.8 km/s, and reaching it is the job of a rocket, as how rockets work explains.

Gravity has not switched off up there. Astronauts float because they and their spacecraft are falling together. Further out, the pull is weaker, so higher orbits are slower and take longer to go round. Travel fast enough, about 11.2 km/s from Earth's surface, and a spacecraft escapes Earth's pull altogether.

Low Earth orbit

Low Earth orbit stretches from just above the atmosphere to about 2,000 km up. It is the busiest neighbourhood in space, because being close to Earth brings sharper pictures, quicker signals and a shorter climb from the ground.

The International Space Station lives here, about 400 km up. It travels at about 28,000 km/h, or 7.7 km/s, and completes an orbit in roughly 92 minutes, so its crew sees about 16 sunrises a day. It has been continuously crewed since November 2000.

Earth observation satellites use low orbits to photograph crops, forests, rivers and cities in fine detail. Large constellations of small, fast-moving satellites also work here to provide connectivity, passing each connection from one satellite to the next as they sweep overhead. The trade-off is that each satellite sees only a patch of Earth at a time.

Medium Earth orbit and satellite navigation

Medium Earth orbit covers the wide band from about 2,000 km to 35,786 km. Its best-known residents are satellite navigation satellites, which fly around 20,000 km up and circle Earth about twice a day.

Each one carries extremely precise clocks and broadcasts its position along with the exact time each signal left. A phone or car receiver listens to several satellites at once, compares how long the signals took to arrive and works out where it is. The same signals carry precise time, which quietly keeps phone networks and power grids in step.

Geostationary orbit

At 35,786 km above the equator, something neat happens. A satellite there takes one sidereal day, 23 hours and 56 minutes, to go round once, the same time Earth takes to spin once relative to the stars. Seen from the ground, it appears to hang still in the sky.

That is why a satellite television dish can be fixed in place, pointing at the same spot for years. It also suits weather satellites, which can watch the same vast stretch of the planet around the clock and follow storms as they grow.

The catch is distance. Signals need a noticeable fraction of a second for the round trip, which is why calls routed through geostationary satellites can feel slightly delayed. The space signal delay calculator shows how distance turns into delay, from the Moon to the outer planets.

Sun-synchronous and other special orbits

Some orbits are chosen for timing rather than height. A sun-synchronous orbit is a low orbit passing close to the poles, tilted so the satellite crosses each place at the same local time every day. Because the light looks the same on every pass, images taken months or years apart can be compared fairly, which is ideal for tracking crops, forests, ice and water.

Polar orbits in general let a satellite see the whole planet over time as Earth turns beneath it. Highly elliptical orbits swing far out and linger over high latitudes, helpful where geostationary satellites sit low on the horizon. Transfer orbits are stepping stones that carry a spacecraft from one orbit to another.

Constellations, explained

In space, a constellation is not a pattern of stars but a team of satellites working together. A single satellite in low orbit sees only a small area and passes over quickly, so continuous coverage needs many, spaced out so that at least one is always in view.

Satellite navigation relies on a constellation in medium Earth orbit. Newer constellations in low orbit bring connectivity to ships, aircraft, farms and remote villages, while Earth-imaging constellations revisit the same places often, so changes show up quickly. Some satellites pass data to each other by radio or laser before sending it down to ground stations.

Satellites and orbits in everyday life

Most people use satellites many times a day without noticing. The services built on their data form one of the layers in the space economy explorer. Here are some of the jobs they quietly do:

• Navigation: directions on your phone, deliveries, shipping and flights.
• Weather: images and measurements behind daily forecasts and storm warnings.
• Maps and cities: up-to-date maps and help planning roads, parks and homes.
• Timing: precise signals that keep phone networks and power grids in step.
• Connectivity: internet and calls for ships, aircraft and places far from cables.
• Farming: spotting thirsty or struggling crops so water and care go where they are needed.
• Disaster response: mapping floods and wildfires quickly so help reaches the right places.

Keeping orbits clean and safe

Old satellites, used rocket stages and small fragments are known as space debris. At orbital speeds even a tiny piece carries a lot of energy, so a collision can damage a working satellite and scatter more fragments.

Operators track objects and nudge satellites aside when a close approach is predicted. AI increasingly helps sift the tracking data and flag the approaches that matter, while people make the final call, a theme explored in AI and the space economy.

Prevention matters most. Many satellites are now designed to leave orbit at the end of their working lives: those in low orbit lower themselves to burn up in the atmosphere, while geostationary satellites move a little higher into a disposal orbit, out of the way. People are also exploring robotic servicing to refuel or repair satellites, and ways to collect old debris.

Try it yourself

The orbit calculator turns these ideas into numbers. Pick an altitude to see the orbital speed, the time for one orbit and how many orbits fit into a day. A few to try:

• About 400 km, where the International Space Station circles in roughly 92 minutes.
• About 20,000 km, where satellite navigation satellites go round about twice a day.
• 35,786 km, where the period stretches to one sidereal day and a satellite appears fixed in the sky.

Nicole Junkermann's perspective

Nicole Junkermann tends to see orbit the way she sees other foundations of modern life: as infrastructure. Navigation, forecasts and network timing all depend on satellites that people rarely notice but rely on every day. As her website puts it, “I invest in infrastructure that builds trust.”

In her view, that trust is earned over long horizons. Satellites can take years to design, build and operate, which is one reason she has long argued that patient capital matters for deep technology, and keeping orbits clean is part of the same responsibility. For a plain-English look at how investors think about the sector, read the future of investing in space.