NASA testing interplanetary internet

The aim of the "interplanetary internet" is to network space modules with the same flexibility as on Earth.
Source: NASA The US National Aeronautics and Space Administration (NASA) says that in recent weeks it has successfully tested a new internetworking protocol specially designed for space conditions. This will later become the basis for an "interplanetary internet" spanning the solar system, enabling communications between space stations and vehicles, satellites, unmanned probes, space-faring robots, ground stations and inhabitants of moon and Mars bases. The development of such a "Deep Space Communications Network" was initiated about ten years ago by NASA together with Vint Cerf, one of the developers of the TCP/IP (Transmission Control Protocol/Internet Protocol) protocol suite that today defines the standard for computer networking.

In order to cope with the special circumstances of space communications ranging over millions or billions of kilometres, with signal propagation times measured in hours, NASA scientists and Cerf evolved a design for "delay- and disruption-tolerant networking" (DTN). While in TCP/IP networks, for example, continuous end-to-end connections are a prerequisite for successful data transfer, and packets are simply discarded if they can't be delivered within a defined time, DTN uses store-and-forward methods in which each intermediate station retains the data to be conveyed until they have been successfully transferred to the recipient.

NASA says that delay- and disruption-tolerant networking has now been tested with a total of 10 nodes, the most important of them being the Deep Impact space probe, now known as the "Extrasolar Planet Observation and Deep Impact Extended Investigation" (EPOXI) mission. The EPOXI node being of particular significance because, unlike the other nine nodes, which were all located on Earth at the Jet Propulsion Laboratory (JPL) in Pasadena, California, and simulated Mars modules or control centres, EPOXI is now flying through space about 32 million kilometres away from Earth, heading for comet 103P/Hartley 2.

Since the EPOXI space probe has two redundantly designed computer systems of sufficient processor power – RAD750 motherboard with 133-MHz PowerPC G3-class CPU and a total of one gigabyte of memory. It was hastily reprogrammed by a software update so that it could serve as a temporary research station for the new DTN protocols. Communications were effected via the parabolic antennas of NASA's Deep Space Network (DSN), which has been in operation since the 1960s. Starting in October, EPOXI was then put into the role of a virtual Mars orbiter twice a week, to function as a DTN data node. According to NASA, the material transferred was mainly images.

Adrian Hooke, NASA's head for the project, said this was the first step on the way to a completely new space communications system. While control centre teams at present have to establish connections to space probes manually and input data transfer commands by hand, this could in future be largely automated using DTN. Vint Cerf most recently explained the advantages of DTN in an interview with Technology Review. The wish, he said, was to create a protocol suite that gave similar network flexibility in space to what was known on Earth. So the interplanetary internet primarily implied developing a number of communications standards and technical specifications in order to run a variety of network applications under space conditions.

Cerf said the most important thing was finally to have standardised protocols enabling many space vehicles to be networked with each other – regardless of what nation had launched them into space. Over time, new missions would be launched and they would begin configuring the backbone capabilities of the network. Each new mission would then add a further node. The hope was then to integrate DTN protocol applications into the terrestrial internet, and also download them to the International Space Station for testing purposes. Ultimately, this network would run continuously and would later form part of an interplanetary communications system when new deep space missions carrying this technology were launched.

Cerf, the "father of the Internet", also sees dangers, however: with such a technology, he said, there were of course possible security considerations. He said appropriate caution had been observed and defensive structures had been directly implemented in the design. Each node would first verify the identity of every other node it communicated with, and would refuse to forward data in the absence of definite identification. Strong authentication and cryptographic methods would be used in order to ensure that resources were only used by parties who were genuinely entitled to do so. The next step is for the DTN software to be loaded into the computers of the international space station (ISS). Demonstrations are planned for summer 2009.

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