Pushing the Internet Into Space
By Joanna Glasner | Also by this reporter
02:00 AM Mar, 14, 2006 EST
Currently, it can take about 40 minutes to relay information from a Mars rover to a NASA scientist -- a rather amazing feat, considering the data has between 100 million and 400 million kilometers to travel.
But to Adrian Hooke, that's still too long to wait.
Hooke, manager of data-standards programs at NASA, says it is technically possible to build a system allowing for interactive communication between humans and machines about as far away as the moon. Meanwhile, across greater distances in space, researchers are finding ways to maintain dialogs despite frequent disruptions.
"There isn't a lot of interaction in interplanetary communications…. Everything tends to be done in a store-and-forward mode," said Hooke. "We're extending internet-like communications into highly disrupted, highly stressed communications environments."
Forget the world wide web. Through a project called the interplanetary internet, Hooke and networking guru Vint Cerf, co-creator the internet's TCP/IP protocol, have been working for the past six years to develop a standard for communicating in disconnected environments, where an uninterrupted two-way dialog isn't possible. The approach is called delay-tolerant networking and relies on communications technologies designed for use in remote places like deep beneath the sea or out in space.
In December, a group of researchers including Cerf submitted a draft proposal for a delay-tolerant networking architecture to the research group studying the technology. The architecture revolves around what researchers call a bundling protocol, used for keeping large quantities of data in a single unit. The approach contrasts to the packet-switching technology used to transmit data on the internet, in which information is chopped into smaller bits, transmitted to its end destination, and then re-assembled.
Hooke used a dropped cell-phone call to illustrate the bundling concept. If the phone network had used a bundling protocol, the person on the receiving end of the conversation would later get to hear the part of the conversation that was missed when the call was cut off.
While the technology is still a work in progress, recent space transmissions, including one involving the Mars rover Spirit, offer a sort of prototype version of what the interplanetary internet will look like, Hooke said. The rover sent a transmission to the European Space Agency's Mars Express, an orbiting craft, which then transmitted the data to Earth.
Another early iteration of the interplanetary internet concept is a standard called Coherent File Distribution Protocol (CFDP), used in spacecraft including the Deep Impact mission, the Messenger probe to Mercury. CFDP allows an instrument to record an observation in a file and transmit the file to Earth without having to consider whether physical transmission is possible at that time, according to the Consultative Committee for Space Data Systems, an international body that develops space communications standards.
"It has a lot of the attributes of the interplanetary internet built into it," Hooke said. "You could make an argument that as more missions pick up CFDP, we'll have the beginnings of the interplanetary internet."
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