South Pole selfie demos deep space communications
What do selfies from the South Pole have to do with deep space missions? Quite a lot, actually. On November 20, NASA used a selfie taken outside Antarctica's McMurdo Station at the bottom of the world and sent to the International Space Station to show off a new technology called Disruption Tolerant Networking (DTN). This communication technology will allow spacecraft far from Earth to communicate with mission control using an interplanetary version of the internet.
The internet is an excellent way of moving data from one part of the world to another, but it does have its limitations. One of these is that it's designed with the assumption that it's connections from point A to point B can be kept uninterrupted or, if it is broken and can't be established by another route, it's possible to restart sending the data packets.
That's fine on Earth where there are trillions of potential connections across the information superhighway, but deep space missions usually rely on one data link that can be interrupted by distance, the Sun getting in the way, or plain bad luck. If that one link is broken, important mission telemetry and other data can be lost forever. So, though internet technology is very useful for space communications, it does need some important tweaking.
This is where McMurdo and DTN come in. With its remoteness, high latitudes, stormy weather, and scant infrastructure, Antarctic data transmission suffers from demand exceeding capacity and the constant threat of information being lost due to outages. It's a pain, but it also makes places like the South Pole a perfect analog for trying to stay in touch with a Mars rover or a Jupiter orbiter.
DTN sends information much the same way as the conventional internet does. Information is encoded and broken into packets, which are bundled and sent through the system to its destination. But, unlike the internet, if a connection isn't available, DTN stores the bundle until communications are re-established. The bundles can then be sent and the file reconstructed at the destination.
For the demonstration, the selfie was taken with a smartphone camera and the DTN software sent the image file from the McMurdo ground station to NASA's White Sands Complex using the repurposed Tracking and Data Relay Satellite (TDRS). When the transmission reached North America, a series of DTN nodes routed the data bundles to NASA's Marshall Space Flight Center in Huntsville, Alabama, from which it was transmitted to the ISS using another TDRS link. On the space station, the bundles were collected by the Telescience Resource Kit demonstration payload and a final DTN node reconstructed the image.
According to NASA, the open-source DTN technology can not only ensure secure communication links with spacecraft, but can also find applications of Earth – in Antarctica, but also in disaster areas and other places that suffer from disrupted communications.
"We're cutting our teeth on this software, in real field conditions," says Patrick Smith, technology development manager for polar research support with the US Antarctic Program. "The simplicity of transmitting from a smartphone could have significant implications for increasing and diversifying the science we support in the polar regions. This represents a vision of how our remote autonomous field research instrumentation might operate one day."
The video below explains the concept of DTN.