NASA stretches the internet 20 million miles
By Matthew Sparkes
Posted on 19 Nov 2008 at 07:49
NASA has conducted the first deep space trials of its interplanetary internet project, transmitting dozens of images to and from a probe 20 million miles from Earth.
The project is designed to link together spacecraft and base-stations in a fault-tolerant and always-on network that is loosely based on the current internet infrastructure used on Earth.
The space agency conducted a month-long test of the protocol using the Epoxi spacecraft as a guinea pig. The small probe is currently far out of Earth orbit on a path to intercept Haley's Comet in 2010. During the trial the probe successfully communicated with nine other nodes on Earth, which were set up to simulate various spacecraft and control centres.
The Disruption Tolerant Networking (DTN) protocol is modelled on the TCP/IP structure of the traditional internet, but is built to withstand far higher numbers of lost packets, as well as delays of up to 20 minutes due to the enormous distances possible between nodes.
To overcome these disruptions, the DTN software takes a unique approach to forwarding packets. If a packet is not successfully transmitted there may well be no alternative route to forward it through, so once sent it, is kept by the sending device until confirmation of receipt is received.
Once operational the network will allow far easier communication between spacecraft of all sorts, allowing simpler transmission of commands and scientific data.
"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," says Leigh Torgerson, manager of the DTN Experiment Operations Center at NASA's Jet Propulsion Laboratory. "With standardised DTN, this can all be done automatically."
The tests follow successful trials earlier this year of traffic between a ground-based station and a satellite in low-Earth orbit. Data was successfully transmitted between the UK-DMC satellite built by Surrey Satellite Technology and a node on the Earth's surface, but these latest tests prove that the protocol can work at far greater distances.
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