With these words Astronaut TJ Creamer (@Astro_TJ on Twitter) sent the first live tweet from space on January 22 using the newly installed internet connection aboard the International Space Station (ISS).
It’s hard enough to set up a reliable wireless network at home on Earth, let alone space. I harbor a personal grudge against my two-foot-thick 19th century brick/plaster wifi-killing walls and don’t get me started with my router or my ISP. So how does NASA connect with the ISS 300 to 400 kilometers above the Earth travelling at nearly 28000 km/h?
In this case, engineers took advantage of the station’s existing communication link, which relies on the Ku radio band. The Ku band is the most common portion of the frequency spectrum used for satellite communication and is not reserved for restricted use. Among the companies that use the Ku band for commercial purposes are satellite internet providers and news networks broadcasting on satellite from remote locations.
A software modification was all that was needed to dedicate a portion of the existing communication network for personal internet use.
“The system will provide astronauts with direct private communications to enhance their quality of life during long-duration missions by helping to ease the isolation associated with life in a closed environment,” NASA stated in a press release announcing the upgrade. The internet connection should have little to no effect on the actual day to day maintenance of the station or its scientific mission.
Tweeting from space may be convenient, but some scientists are working on a much tougher space-based networking problem. Currently, satellites, probes, landers and other unmanned spacecraft each have a unique communication link with Earth. Vinton Cerf, one of the co-inventors of the TCP/IP internet protocol, has been working with NASA for over a decade on a robust protocol that could integrate different space based communication devices to work together like an Earth based system of routers, switches and clients.
Dubbed Disruption Tolerant Networking, or DTN, the protocol is designed to deal with the interference and unpredictability of interplanetary communication signals.
While there are no wifi blocking walls in space, these networks struggle with intermittent, unpredictable and easily degraded signals. Transmission scrambling solar storms, blackout periods when a spacecraft is on the far side of a planet and the enormous distances that signals must travel all add up to a large number of corrupted or lost data packets. On Earth we’d just query the source again and start the transmission over, but without reliable continuous connections this just isn’t feasible.
“You are going to be able to communicate from A to B at this data rate starting at 12:30 and ending at 3:30, and then you are not going to be able to communicate on that link anymore...until next Tuesday,” said Scott Burleigh, a software designer at NASA’s Jet Propulsion Laboratory, in an interview with IEEE Spectrum last July for an article on the particulars of DTN.
Overcoming these obstacles outside of Earth’s orbit are going to be the real space communications challenge.
It’s great that astronauts can tweet from space, update their Facebook accounts and browse a friend’s Flickr album, but this personal internet upgrade is not exactly a revolution in communication.
When we get a live tweet from one of the Martian Rovers though, I’ll be impressed.
[Top photo credit: NASA March 23, 2009]