Astronauts and the Internet – the final frontier
Twenty years ago, this would have been nothing short of miraculous – the tentative first steps were being made in university computer labs; laborious procedures were required to entice anything worthwhile from this mysterious ‘Internet’; the excitement when you’d been ‘at NASA’ – on what at the time was an extraordinarily rudimentary homepage created by our US colleagues ...
So what about astronauts on the International Space Station (ISS)? How do they connect to the Internet? To find out, I got in touch with Ivano Verzola, one of our experts for the 'Data Management System' on the Space Station. His daily work on the console here with us at the Columbus Control Centre (Col-CC) revolves entirely around our on-board computers, how they communicate, the MIL-busses, LAN switches, file transfers, the data rates via S- and Ku-band and the bus controllers and remote terminals. I've turned to him for advice quite frequently during shifts when our computers seem to be having another of those 'wilful' days. He's bound to know whether astronauts can access the Internet.
Ivano Verzola is one of the experts in the Columbus Control Centre responsible for the data system on board the ISS. Credit: DLR (CC-BY 3.0).
I’m familiar with the first part of the story; broadly speaking, satellites communicate with one or several selected ground stations and only have contact with them during their brief overflight before 'going dark' for several hours. But the TDRS satellite system that NASA shares with the US military and others enables almost permanent contact between ourselves and the ISS. These satellites, positioned in geostationary orbit (so that they always appear at the same point in the sky when viewed from Earth), 36,000 kilometres out in space, receive their data from a small number of ground stations and then pass the information on to the ISS, flying at a lower altitude and almost always in range of one of these satellites. And the data from the ISS to the ground stations simply travels back in the opposite direction. So what is the 'data' here? Six video channels from the Space Station, four 'space-to-ground' radio channels, data streams from on-board experiments, commands to the ISS and all the status data that we refer to as telemetry, which we use to monitor the ISS and all of its subsystems.
The three NASA 'Tracking and Data Relay Satellites' (TDRS), used mainly for the ISS, essentially cover the space station's entire orbit. This requires two antenna systems, one in White Sands and one on Guam Island. We then receive our data via Houston or Huntsville. Credit: DLR (CC-BY 3.0).
Behind all of this is radio – encrypted, of course – at S-band and Ku-band. Theoretically, this radio connection even allows us to swap emails with the astronauts; they can surf the web or make telephone calls by Voice over IP.
Why only 'theoretically'? Well, everything is a bit different compared to what we are used to here on Earth.
Firstly, it is only possible to connect if there is an active radio contact via Ku-band. Astronauts will experience brief interruptions in the connection – either because the ISS antennas are currently realigning to contact the next satellite or because none of the satellites booked for the ISS are available for a few minutes. After all, there are other users of the TDRS system, too. Secondly, strict rules govern writing emails to astronauts, for example. Only emails from senders whose name is on a list maintained by the crew will be passed to the ISS. Each email initially passes through Houston, where it is checked and scanned for viruses; only then is it shared via the 'mail sync'.
The possibility of direct Internet use in space hasn't been around for very long, either. Initially, it was completely impossible. Then, there was a detour via a server in Houston. Now, there is a direct connection, even if the speed leaves quite a bit to be desired compared with standard DSL. Ivano tells me there are special laptops on the Space Station, equipped with this 'connection to Houston' – the Station Support Computers (SSC). Spread across the Station, they are connected to the Joint Station LAN (JSL), or access it via Wi-Fi. Astronauts use them to log on to the Internet – or telephone their families or us, the Flight Controllers – with video images in both directions if they wish.
The astronauts cannot use these laptops to send commands to the Space Station. This strict separation is deliberate, intended to leave no possibility for abuse, viruses or 'cyberspace' attacks. "Everything related to the network and computers on the ISS is considered highly sensitive," Ivano tells me by way of explanation. And he should know; just recently, a new and important function was installed on the laptops aboard Columbus. The man behind it all? Ivano.
Top image: Credit: DLR.
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