NASA has announced successful space tests of its new purpose-designed interplanetary communications networking protocol, which it calls Disruption-Tolerant Networking (DTN). Famed TCP/IP pioneer Vint Cerf was instrumental in the space net's design.
"This is the first step in creating a totally new space communications capability, an interplanetary Internet," said Adrian Hooke, at NASA Headquarters in Washington.
According to the space agency, DTN differs significantly from the normal Internet's Transmission-Control Protocol/Internet Protocol, TCP/IP. The Interplanetary Internet is designed to be more robust, so as to cope with the huge latencies of space communication and the long interruptions which occur during solar storms or when a spacecraft moves behind a planet. The lightspeed delay to and from Mars is anything from three-and-a-half hours to 20 minutes, for instance.
Unlike TCP/IP, the DTN does not assume a continuous end-to-end connection. If a destination path cannot be found, data packets are not discarded. Each node keeps the information as long as necessary until it can communicate safely with another node. This "store-and-forward" method means that information does not get lost when no immediate path to the destination exists. Eventually, the information almost always gets through.
"In space today, an operations team must manually schedule each link and generate all the commands to specify which data to send, when to send it, and where to send it," said Leigh Torgerson, manager of the DTN Experiment Operations Center at NASA's Jet Propulsion Laboratory in California. "With standardized DTN, this can all be done automatically."
A month-long series of DTN demonstrations began in October, according to NASA. There were 10 nodes on the test interplanetary network. One was the Epoxi craft 20 million miles into space, simulating a comms relay platform in Mars orbit. (In reality, Epoxi is on a comet-encounter mission.) The other nine were simulated landers, orbiters and Earth mission-control stations - in actuality located at JPL. The tests went well according to NASA, with "dozens" of images successfully passed between Epoxi and the other nodes.
A NASA-wide demonstration using DTN software loaded on board the International Space Station is scheduled to begin next summer. ®