Stephen Withers
Wednesday, 19 November 2008 03:12
Science -
Space
Page 1 of 2
It's been a decade in the making, but NASA has successfully tested a new deep-space communications network modelled on the Internet. Images have been transmitted to and from a spacecraft 20 million miles away.
Space communications are more prone to disruptions than their terrestrial counterparts, and the huge distances involved result in massive latency.
For example, a spacecraft may be unreachable due to solar storms, and depending on the relative positions of Earth and Mars in their orbits, a radio signal can take between 3.5 and 20 minutes to travel between the planets.
For those reasons, a protocol such as TCP/IP is unsuited to the task of deep space communication as it assumes continuous connection.
So ten years ago, NASA and Vint Cerf - the co-designer of TCP/IP and currently a vice president at Google - started work on Disruption-Tolerant Networking (DTN) to meet the needs of space communication.
Rather than abandoning packets of data that can't be delivered, DTN uses a store-and-forward strategy, holding onto packets until they can be transmitted to another node in the network. The process continues until the packet reaches its final destination.
"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 JPL.
"With standardized DTN, this can all be done automatically."
So what did the tests involve, and what is the next step? See
page 2.
