With more nations sending up more spacecraft conducting more advanced scientific studies, how will the world's space agencies keep everyone and everything in the loop? NASA has devised a system, touted as a sort of deep-space Internet protocol, to form the backbone of interplanetary communication: Disruption-Tolerant Networking, or DTN. The space agency announced this week that its DTN network, which would allow the automated relay of information to and from far-flung spacecraft or landers via intermediate points, had passed its first test, relaying info millions of miles into space.
"Right now most of our missions are 'point-to-point,' i.e., one ground system talks to a single spacecraft over a single space radio link," says Adrian Hooke, manager of space networking architecture, technology and standards for NASA. Communication with Mars landers or rovers, in contrast, is a "two-hop" system, he says—one link from the ground to an orbiter around the Red Planet and another link from the orbiter to the Martian surface. "Typically those two space links are rarely both up together, so we have the orbiter 'hold' data until the next hop becomes available."
The problem is that managing all those relays with ground-based technicians takes a lot of manpower. "As you add more spacecraft that need to talk to each other through more and more space links, it becomes increasingly impossible to manually set up all of the data flows," Hooke says. The new DTN protocol, he says, reduces the reliance on human management by allowing spacecraft along the way to act as automated nodes on the network, passing along data when links are available or holding onto messages until a clear communication channel can be established.
NASA's recent test involved just one space-borne node, the EPOXI spacecraft, about 20 million miles from Earth. The other nine nodes were on the ground at NASA's Jet Propulsion Laboratory in Pasadena, Calif. But if DTN continues to pass muster, Hooke says, the network should be ready by 2012 for use on missions in 2015 and beyond—when the next-generation Constellation manned transport system is projected to replace the space shuttle.