Satellite Communications

Podcast Transcript

Once humans managed to put artificial satellites into orbit, the next question was, “what can we do with this?”

One of the first applications of satellites, and still one of the biggest uses still today, has been for communications.

Using satellites for communications requires cutting-edge technologies in space flight, solar power, radio engineering, and computers.

Learn more about satellite communications, its history, and how it works, on this episode of Everything Everywhere Daily.

The origin of satellite communications actually goes back to before the first satellite was put into orbit.

The British science fiction author Arthur C. Clarke had been a proponent of the idea of space travel since the 1930s. In 1945 he wrote an article for Wireless World magazine titled “Extra-Terrestrial Relays – Can Rocket Stations Give World-Wide Radio Coverage?”

In this article, he proposed the idea that if a satellite were put into the correct orbit, the time it took to orbit the Earth would be precisely the same amount of time it took the Earth to rotate on its axis.

The end result would be that a satellite would stay in one spot above the Earth, just as if it were hung on the ceiling. It is known as geosynchronous orbit.

The location of this orbit lies 35,786 kilometers or 22,236 miles above the equator.

A satellite in such a spot could receive a radio signal from anywhere on Earth that could see it and could send a radio signal to anywhere on Earth that it could see.

It was this potential for satellite communications that was one of the biggest driving forces behind the very early space race.

The first thing that could even be called a communications satellite was the SCORE satellite, launched in December 1958. SCORE stood for (Signal Communications by Orbiting Relay Equipment).

All it was was a tape recorder that could receive, record, and transmit voice messages. It was by far the largest object put into orbit at the time as it was 80 feet or 24 meters long… but it was only in orbit for a month.

In 1960, NASA launched the first passive communications satellite, known as Echo 1. Echo 1 was nothing more than a giant, metallic balloon that orbited the Earth.

Radio signals would be sent to the satellite, which would then be reflected back down to Earth. It was incredibly simple but not very sophisticated and didn’t work very well.

The satellite which is usually considered the first true communications satellite was Telstar, which was launched in 1962. Telstar was created by Bell Labs, which, if you remember back to my previous episode, invented everything.

Several things made Telstar different from previous satellites. For starters, it was solar-powered with the ability to produce 14 watts of power. Second, it contained a new electronic device called a transponder.

A transponder is a device that will receive a radio signal and then rebroadcast that signal after amplification. It has become a critical component of all communication satellites ever since.

Unlike Echo 1, Telstar was an active system, not a passive system.

Telstar set a host of firsts for a communications satellite, including the first live transatlantic television broadcast, the first satellite telephone call, the first satellite telefax image, and the first data sent by satellite.

Researchers were able to synchronize clocks in the US and the UK down to within 1 microsecond, which was 2,000 times better than before.

Telstar, however, wasn’t in a geostationary orbit. That meant that parties on either side of the Atlantic could only use the satellite for 30 minutes of each 2 ½ hour orbit.

Telstar functioned for about four months before it went out of service, and it is still up in orbit today, non-functioning. Despite its short life, it was considered a huge hit, having conducted hundreds of broadcasts.

The next big innovation was the launch of the first satellite to be parked in geosynchronous orbit.

Here I should briefly explain the difference between geosynchronous orbit and geostationary orbit.

A geosynchronous orbit is any orbit that has the same orbital period as the rotation of the Earth. I should note that a day in this context is a sidereal day, not a solar day. This would mean an orbit of 23 hours, 56 minutes, and 4 seconds.

A satellite, however, can have an orbital period of 1 day but not be in one spot in the sky. Its orbit could have slight inclination and eccentricity, in which case it will appear to do a figure-eight in the sky. It would be roughly in the same spot, but not exactly in the same spot.

A geostationary orbit is a geosynchronous orbit with almost no inclination or eccentricity. It orbits on a plane parallel with the Earth’s equator.

The first satellite to be put into geosynchronous orbit was Syncom 2, launched in 1963.

Like Telstar, Syncom 2 had several firsts, including the first satellite call between heads of state when President John Kenney called the Nigerian Prime Minister Abubakar Tafawa Balewa.

In 1964, Syncom 3 became the first satellite to be put into geostationary orbit.

While these satellites were a success, the real question was how satellite communications were going to used for commercial purposes.

The United States addressed this by passing the Communications Satellite Act of 1962.

This allowed for government regulation of satellite communication and also allowed for every communications company licensed by the FCC.

This led directly to the creation of Communications Satellite Corporation or COMSAT. COMSAT was a public/private partnership to use communication satellites.

Another organization, known as the International Telecommunications Satellite Organization or INTELSAT, was an intergovernmental consortium that managed communication satellites.

The reason for these organizations was that geostationary communications satellites were really expensive, far beyond the reach of something like a television network.

For the most part, companies didn’t need a full-time satellite at this time. A TV network might file a story from another country, and they would just need to book a time to send the video back to their headquarters.

The first commercial communications satellite was INTELSAT 1, which was launched in 1965.

The Soviets, despite all their early accomplishments, were behind the Americans when it came to satellite communications. They neither had the money, technology, nor the market to support large-scale communications satellites.

They launched their first communications satellite in 1965 as part of the Molniya Program. These Soviet satellites were very unlike the American communications satellites in one major respect.

The Soviet satellites were designed for domestic use, in particular for communications in polar regions.

The thing is, geostationary satellites don’t work very well if you happen to live in extreme northern or southern latitudes. I remember visiting Iceland once and noticed how all the satellite TV dishes were pointed not up in the air but almost at the horizon.

The Soviets used what is now known as a Molniya orbit. It is a highly elliptical orbit that spends most of its time over the poles. Unlike a geostationary orbit, the satellite is constantly moving in the sky, and it isn’t available all the time. However, if you happen to live in the arctic, it is much better than nothing.

Satellite communications grew over the next few decades. Improvements in electronics and solar panels made for much better satellites, and improved launch capabilities allowed for bigger satellites.

When something was “Live via Satellite,” it was usually a major event like an Olympics or something.

One of the first and biggest satellite events took place on January 14, 1973, when Elvis Presley performed in a concert called Aloha from Hawaii via Satellite. It was broadcast live in Australia and Asia.

Starting in the mid-70s, entire satellite-based television networks started to spring up. These networks would use Ku band satellite channels to send their network signal to cable TV operators, who would then play the network feed locally.

If you happened to own a large Ku band satellite dish, you could actually pick up these stations directly as they had an analog signal.

These systems were large and expensive, however.

They were eventually replaced by smaller digital dishes, which were sold directly to consumers. Because the signal was digital, it could be encrypted, which means access could be controlled. They also offered more channels and a higher quality signal.

Television turned out to be the ideal use for satellites because it only requires a one-way signal. Millions of people could catch the signal sent by a single satellite because nothing was sent back up to orbit.

The same holds true for digital satellite radio, which began in the early 2000s.

It turns out that geostationary satellites are not very good at two-way communication. For starters, you need a channel for every user, which can get really expensive quickly. Furthermore, geostationary orbit is a long way away.

To put it into perspective, geostationary orbit is about 90 times further away from Earth than the International Space Station. It is far enough away that the speed of light starts to become an issue. Round trip from Earth to geosynchronous orbit and back takes about a quarter second for light.

If you have ever been on a cruise ship or a remote island and have tried using satellite telephones or internet, you’ve experienced just how bad and expensive it is.

The solution to this has been known for a while, but it was very difficult to build: a network of low Earth orbit satellites.

The approach is totally different from a geostationary satellite. Instead of one satellite very far away that doesn’t move, you have a whole bunch of satellites much closer to Earth that are constantly moving overhead.

The first company to propose a satellite network like this was Teledesic. They were founded in the 90s by cell phone network pioneer Craig McCaw and Microsoft founder Bill Gates.

They spent billions of dollars but never managed to actually launch a satellite.

Several companies have proposed similar systems, including Amazon and OneWeb. However, to date, only one company has really been able to deploy a serious low Earth orbit data network: SpaceX.

Their Starlink network currently has over 2,700 satellites in an orbit of 550 kilometers.

By keeping the satellites that low, the time for signals to travel from space to the ground is minimal. Because there are so many, each satellite is able to provide more bandwidth to a smaller number of people they happen to pass over at the time.

The Starlink system is like a reverse cellular network. In a normal cellular network, you move around a network of fixed antennas. With Starlink, the antennas are moving, and the receivers are (relatively) standing still.

The reason why SpaceX is able to make it work where a company like Teledesic wasn’t is primarily that they own their own launch vehicles. They have decreased the cost of sending a kilogram to orbit by almost a factor of 10 by reusing rockets.

The satellites they use are small and mass-produced, unlike traditional communication satellites, which are big and custom-built. A typical launch will send 40 Starlink satellites into orbit at once. If and when the Starship system starts to launch, that might increase to 400 per launch.

Current users are able to get speeds between 200-300 Mbps, even in remote areas, with ping times less than 30 ms.

Currently, the satellites just send signals back to a ground station within sight.

The next generation of satellites will be able to send data to each other via laser connections to route data in the vacuum of space. In theory, this will be faster than a fiber optic cable for routing data around the world because light travels faster in a vacuum than in fiber.

As this is just a data connection, you can also use it for voice, video streaming, or anything else you would use an internet connection for.

Future plans are for as many as 40,000 satellites which would provide high-speed connectivity everywhere from Antarctica to Andorra.

Another difference between a low Earth orbit system and a geostationary system is the type of antennae. Geostationary satellites require a dish-shaped antenna you’ve probably seen. This is used to amplify the weak signal to the receiver.

A low Earth orbit system uses what is called a phased array antenna. It is usually just a flat and points up, but it can electronically move where it is sending and receiving the signal from, as the satellites are moving overhead.

A dish antenna is rather dumb, but a phased array antenna is an expensive piece of electronics.

I should end by noting one other type of satellite communication that most people might not think of.

Ham radio operators have dabbled in satellite communications. They have managed to get a few cheap microsatellites into orbit, which are used by hobbyists.

However, there is another technique that some ham radio operators use that involves a satellite. It is called EME communications, which stands for Earth-Moon-Earth.

It was first proposed and tested in the 1940s, and it does indeed work. You point a transmitting antenna at the moon, and then a very weak signal bounces back to Earth. You need an enormous antenna to receive it, but it can be done if you can tolerate a 2.5-second delay.

I’ve been fascinated by satellite communications for years, and I continue to be. We are now entering a new era where satellites will be able to bring fast, affordable connectivity to everyone on Earth, regardless of where they live.