Starlink is an interesting architecture. There are three main components. The first is the user terminal. It’s a sophisticated antenna. The second is the satellite, relatively small, mass-produced telecommunications satellites in low earth orbit. The third is the gateway. Gateways are ground stations with 8 antennas each which are connected to the terrestrial internet backbone.
So, the user terminal is the thing that looks like a flat-faced dish and connects to your local network, probably via a wi-fi router (SpaceX provides a router as part of the “kit”.) This “dish” is actually a phased array antenna which is capable of digital steering so it doesn’t have to do physical steering to track the satellites as they move across the sky.
The satellites are very cool. They are designed to be flat-packed so that 60 of them can stack inside one rocket nose cone. They’re rectangular in shape, a slab 9 feet on one side and 4.5 feet on the other with a 30 foot solar array that deploys to give the satellite an L shape. There are currently about 1,000 of them orbiting Earth of a planned 14,000. They fly at super-low orbits and move across the sky in just a few minutes. Their orbits are spread out to ensure there is always a satellite overhead.
The gateways are strategically located to provide overlapping areas of coverage. Each gateway is a collection of 8 antennas that connect the satellites to the ground-based internet at major fiber optic connection points. There are about 40 of these gateways already providing nearly full coverage to the U.S.
So, as a customer, my computer makes a request for something on the internet. It sends that request across my home wi-fi network to the Starlink user terminal which beams it up to a Starlink satellite that’s moving across the sky at 17,000 mph. The satellite beams my signal down to a Starlink gateway where it connects to and races across the fiber optic backbone, eventually finding its way to the requested resource. Then everything happens in reverse as that resource is delivered back to my computer.
But this is just how it works today, with the first generation of Starlink satellite. The second generation of satellite, some of which are already launched, have laser interlinks. Instead of simply relaying the signal from my user terminal directly to a gateway where it travels to its destination on the terrestrial internet backbone, the satellites will talk to each other, becoming a part of the internet backbone itself, in space. This will mean far fewer, but larger gateways will probably become the norm as Starlink coverage expands.
(Perhaps not practically useful, but nonetheless interesting to me, for some connections, especially those that are from one side of the world to the other, the Starlink latency could be lower than the terrestrial fiber optic network’s. That’s because light travels faster in space than in glass.)