Starlink, the low earth orbit satellite constellation from SpaceX, has hit the minimum configuration to provide broadband. So far 482 satellites have been launched, just above the 400 needed for a minimum service. 800 will provide a ‘moderate’ broadband service, and the company aims to have as many as 30,000 satellites in orbit, launching 60 at a time.
“For Starlink, we think of our satellites more like servers in a data centre than special one-of-a-kind vehicles,” said Matt Monson, Director of Starlink Software at SpaceX. He has given some more details of the satellite technology. "Each launch of 60 satellites (above) contains more than 4,000 Linux computers. The constellation has more than 30,000 Linux nodes and more than 6,000 microcontrollers in space right now,” he said. The full ‘megaconstellation’ would have over 360,000 microcontrollers and over a million nodes.
These ‘servers in the sky’ generate huge amounts of data. “We're currently generating more than 5TB a day of data,” said Monson. “We're actively reducing the amount each device sends, but we're also rapidly scaling up the number of satellites (and users) in the system. Doing the detection of problems onboard is one of the best ways to reduce how much telemetry we need to send and store so we only send it when it's interesting.”
There is less redundancy in these LEO satellites than larger geostationary systems that need to last twenty years or more. “We've designed the system so that satellites will quickly passively deorbit due to atmospheric drag in the case of failure," said Monson. "We still have some redundancy inside the vehicle, where it is easy and makes sense, but we primarily trust in having system-level fault tolerance: multiple satellites in view that can serve a user. Launching more satellites is our core competency, so we generally use that kind of fault tolerance wherever we can, and it allows us to provide even better service most of the time."