Sunday, July 12, 2009

NASA wants to take Internet to interplanetary level


nasa_logo Apparently, what leaves most people at awe doesn’t impress the NASA scientists a bit, like chatting with your buddies 8000 miles across continents at real time. NASA wants to put up a communication network that will allow them to chat, or communicate with various probes, rovers, orbiters and spacecraft exploring the solar system - effectively binding them together to form an interplanetary Internet.

At the interplanetary level communication delays are huge, and variable because the planets are in orbit around the sun. Existing communication protocols like the TCP/IP breaks down under such conditions. NASA has been performing tests on more robust network technologies, called Delay Tolerant Networking, or DTN, protocols, the second test of which was successfully conducted on the International Space Station.


The DTN protocols will extend the terrestrial Internet into space by overcoming a number of obstacles, including the extraordinary length of time it takes packets to move between separate hops in a deep-space network, the intermittent nature of network connections, and bit-scrambling solar radiation. On Earth, packets move from source to destination in milliseconds. By contrast, a one-way trip from Earth to Mars takes a minimum of 8 minutes. The constant motion of celestial bodies means that packets have to pause and wait for antennas to align as they hop from planet to probe to spacecraft.

Work on DTN began as early as 1998 and one of the co-inventor of the Internet's TCP/IP protocol, Vint Cerf, is also a key member of the group of scientists working on it.

An initial test of DTN in space last October was successful. The code was loaded on a comet-studying spacecraft called Deep Impact as that probe headed out for a flyby of Comet Hartley 2. "We turned on the software on the spacecraft and on about a dozen nodes on Earth and just left it running, completely automatic for about a month," Burleigh says. During the test about 300 images were transmitted over distances that stretched up to 24 million kilometers. Although a couple of bugs were found, no packets were dropped, and no bits got corrupted. The software even survived the unintentional reboot of one of the Earth-based antennas. "The protocols underneath it were able to recover the data and actually get stuff through," says Keith Scott, a principal engineer at Mitre Corp., in Reston, Va., who has been working on DTN with Burleigh and others.

A key to DTN is a technique called "store and forward." Basically, every node hangs onto the data it receives until it can safely pass it on. On Earth, the data would simply get dumped if there was a problem and be retransmitted by the source.

NASA expects the network to grow, weaving an interconnected Web between the planets, the space station and spacecraft.

[via Maximum PC and]


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