Fly me to the moon (and let us email round the stars)

Ever wondered what your domain name will be on Jupiter or Mars?

A group of experts is creating a protocol to allow spacecraft to communicate as if they are on the internet. Richard Baguley reports on the net's next frontier... The internet is a big place, but if a group of scientists and technicians get their way, it could soon be an awful lot bigger. In fact, it could soon spread to the entire solar system, with emails and data flying between planets in a format that is pretty close to the one your computer uses to read this web page. The InterPlanetary Net Special Interest Group (IPNSIG, at http://www.ipnsig.org ) is a group that is trying to define the new protocol - based mostly on existing internet protocols - for how data is transmitted to and from spacecraft. The idea is intriguing: instead of each space probe using its own way of sending data and receiving instructions, they all use the same protocol. This also allows one spacecraft to store and forward data from another, creating a network the IPNSIG calls the Interplanetary Network, or IPN. For instance: a probe in a Mars orbit could receive data from a probe on the Martian surface and forward this to Earth. Vint Cerf (a member of the IPNSIG and one of the inventors of the TCP/IP protocol) has said: "The IPN can be thought of as a network of internets but it is even
more general because it is OK for some of the components not to be internet-based." Of course, this being a group of techie geeks, the first draft of their proposal contains more than a dash of techie humor, such as the "Desiderata of Interplanetary Internetworking". This contains some of the design ideas of the protocol, such as: "Go thoughtfully in the knowledge that all interplanetary communication derives from the modulation of radiated energy, and sometimes a planet will be between the source and the destination. Therefore rely not on end-to-end connectivity at any time, for the universe does not work that way." However, sending data between planets does require some serious rethinking of existing internet protocols. "Nearly all of the internet protocols we're familiar with - web browsing, file transfer, remote console access - are designed to be used in a conversational, interactive way," said Scott Burleigh of the NASA Jet Propulsion Laboratory, another member of the IPNSIG. "Because of the long delays in propagating signals across interplanetary space, IPN applications need to operate in a fashion that's much more like an exchange of letters than a telephone call." Instead of sending messages and expecting an immediate reply, the IPNSIG wants to create smaller local networks, such as a connection between a Mars probe on the Martian surface and another in orbit. Connecting these local networks are backbone connections between hubs that hold the data and transmit it between the local networks (such as a high-power transmitter on the orbiting probe that sends the data back to Earth when it can). In effect, it's like the post: data is sent without the expectation of getting a reply immediately or even knowing if the letter has arrived. The group is also looking at how to name the different parts of the IPN. What they have come up with so far is to break the address of individual parts of the IPN into two parts: an admin part and a routing part. The admin part explains which system it is and the routing part shows what part of the IPN it is on. For instance, the Earth version of silicon.com would be referred to as silicon.com, earth.sol, while the Martian version would be called silicon.com, mars.sol. They are certainly planning for the long term. "The advances in microspacecraft and autonomous sensor technology suggest there might be thousands or even hundreds of thousands of communicating devices out there by the latter part of this century," said NASA's Burleigh. And if the group has its way, the first one of these probes could be a reality as early as 2004. "An early prototype system that implements many of the IPN architectural concepts may be deployed on a NASA mission called 'Deep Impact' that is planned for a launch in early 2004," added Burleigh. So it is possible that sometime soon, spacecraft will be making their way through the darkness of space beaming back information in a format that's not so far removed from the one your computer uses. Or rather: it will be far removed, but only in the physical sense. As the IPNSIG proposal puts it: "Truly the solar system is a large place and each one of us is on his or her own. Deal with it."