It took 10 years, but legendary Vint Cerf, who is widely credited as one of the scientific founders of the Internet, has helped reach yet another Internet milestone: the first deep-space communications network modeled on the Internet.
NASA announced Nov. 18 that engineers from NASA's JPL (Jet Propulsion Laboratory) used software that Cerf helped develop over 10 years called DTN (disruption-tolerant networking) to transmit dozens of space images to and from a NASA science spacecraft located about 20 million miles from Earth.
"This is the first step in creating a totally new space communications capability, an interplanetary Internet," Adrian Hooke, team lead and manager of space-networking architecture, technology and standards at NASA, said in a statement.
NASA began a month-long series of DTN demonstrations in October, using the EPOXI spacecraft, which is on a two-year mission to Comet Hartley 2, as a Mars data-relay orbiter. The tests are the first in a series of planned demonstrations of DTN. NASA eventually hopes to use DTN on a variety of upcoming space missions.
According to NASA, the Interplanetary Internet could allow many new types of space missions such as complex assignments involving multiple-landed, mobile and orbiting spacecraft. DTN could also allow reliable communications for astronauts on the surface of the moon.
"In space today, an operations team has to 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."
DTN sends information using a method that differs from the normal Internet's TCP/IP communication suite, which Cerf co-designed. Unlike TCP/IP on Earth, the DTN does not assume a continuous end-to-end connection. In a typical TCP/IP design, if a destination path can't be found, the data packets are not discarded.
With DTN, on the other hand, each network node keeps custody of the information as long as necessary until it can safely communicate with another node. This store-and-forward method means that information does not get lost when no immediate path to the destination exists. Eventually, the information is delivered to the end user.
"There are 10 nodes on this early interplanetary network," said Scott Burleigh, JPL's lead software engineer for the demonstrations. "One is the EPOXI spacecraft itself and the other nine, which are on the ground at JPL, simulate Mars landers, orbiters and ground mission-operations centers."
For the next round of testing, a NASA-wide demonstration using new DTN software loaded on board the International Space Station is scheduled to begin in summer of 2009.