[astro] InterPlaNet

[Eugen Leitl]

http://www.universetoday.com/2008/10/28/google-and-nasa-are-working-on-an-interplanetary-internet/

October 28th, 2008

Google and NASA are Working on an Interplanetary Internet

Written by Ian O'Neill

The Interplanetary Internet concept

In an initiative energized by Google Vice-President and Chief Internet
Evangelist Vint Cerf, the International Space Station could be testing a
brand new way of communicating with Earth. In 2009, it is hoped that the ISS
will play host to an Interplanetary Internet prototype that could standardize
communications between Earth and space, possibly replacing point-to-point
single use radio systems customized for each individual space mission since
the beginning of the Space Age.

This partnership opens up some exciting new possibilities for the future of
communicating across vast distances of the Solar System. Manned and robotic
space craft will be interconnected via a robust interplanetary network
without the problems associated with incompatible communication systems…

"The project started 10 years ago as an attempt to figure out what kind of
technical networking standards would be useful to support interplanetary
communication," Cerf said in a recent interview. "Bear in mind, we have been
flying robotic equipment to the inner and outer planets, asteroids, comets,
and such since the 1960's. We have been able to communicate with those
robotic devices and with manned missions using point-to-point radio
communications. In fact, for many of these missions, we used a dedicated
communications system called the Deep Space Network (DSN), built by JPL in
1964."

Indeed, the DSN has been the backbone of interplanetary communications for
decades, but an upgrade is now required as we have a growing armada of
robotic missions exploring everything from the surface of Mars to the
outermost regions of the Solar System. Wouldn't it be nice if a communication
network could be standardized before manned missions begin moving beyond
terrestrial orbit?

"When we launch a spacecraft with a unique set of sensors onboard, we often
end up writing special communication and application software that is adapted
to that spacecraft's sensor systems and manipulators," Cerf said in response
to the challenges space missions face each time they are designed.

The Internet uses standard TCP/IP protocols so billions of online entities
are always compatible. Although there are limitations to the Internet, it has
proven to be a highly flexible and scalable system, so with the help of
Google, NASA hopes to push the Internet beyond Earth. "The Interplanetary
Internet project is primarily about developing a set of communication
standards and technical specifications to support rich networking in space
environments," Cerf added.

This all sounds very interesting, but the challenges with building such a
system require some novel techniques. How do you deal with the limitation of
the speed of light? After all, it can take light 40 minutes to travel
to-and-from Mars, and up to 12 hours to Pluto and back. How do you cater for
planetary rotation? The transmitters/receivers won't always be on the correct
side of the planet. What happens if a satellite signal is blocked by a
planet, the Sun or a moon?

Vint Cerf says the disruption of data transmission has to be confronted with
a delay- and disruption-tolerant networking system, otherwise known as DTN.
"It will allow us to maintain communications more effectively, getting much
more data because we don't have to be in direct line of sight with the
ultimate recipient in order to transfer data," he said.

DTN will be based on store-and-forward methods used by TCP/IP systems; if
there is a disruption in signal, the transmitting station will hold data
packets until the signal is re-established. However, DTN will be more robust,
catering for long transmission lag-times (such as the many-hour light
transmission times between Earth and the outer Solar System). "We have to
cope with the fact that there is a really high potential for delay and
disruption in the system," he added.

Standard TCP/IP protocol should also work seamlessly with the DTN, allowing
planetary missions to have their own distributed Internet whilst using DTN as
a link through interplanetary space.

This has obvious applications for future manned missions to Mars, after all,
can you imagine the first colonists without their own blog?

Source: Technology Review

http://www.technologyreview.com/printer_friendly_article.aspx?id=21601&channel=communications&section=

Monday, October 27, 2008

A Better Network for Outer Space

Why Vint Cerf wants to put Internet-style networking in space.

By Brittany Sauser

Having designed the networking protocols that launched the Internet, Vint
Cerf now wants to put the same kind of robust communications network in outer
space. Currently, astronauts and robotic spacecraft communicate with Earth
using point-to-point radio links and communications schemes that are tailored
to nearly every new mission. This inhibits interoperability and the
repurposing of communications equipment, and as the number and complexity of
missions increases, it will only become more problematic.

Cerf, who is Google's vice president and chief Internet evangelist, is
working with a team at NASA's Jet Propulsion Laboratory (JPL), where he is
also a visiting scientist, and at the MITRE Corporation, based in Washington,
DC, to design and implement a revolutionary new scheme for space
communication. The project, dubbed the Interplanetary Internet, will be
tested aboard the International Space Station (ISS) in 2009, and Cerf hopes
that by 2010, new space missions will be designed to use the protocols.

Ultimately, the network could interconnect manned and robotic spacecraft,
forming the backbone of a communications system that reaches across the solar
system.

Technology Review's Brittany Sauser caught up with Cerf to discuss the
details of the project.

Technology Review: What's the purpose of the Interplanetary Internet?

Vint Cerf:The project started 10 years ago as an attempt to figure out what
kind of technical networking standards would be useful to support
interplanetary communication. Bear in mind, we have been flying robotic
equipment to the inner and outer planets, asteroids, comets, and such since
the 1960s. We have been able to communicate with those robotic devices and
with manned missions using point-to-point radio communications. In fact, for
many of these missions, we used a dedicated communications system called the
Deep Space Network (DSN), built by JPL in 1964.

But one problem with space communication has been the limited use of
standards. When we launch a spacecraft with a unique set of sensors onboard,
we often end up writing special communication and application software that
is adapted to that spacecraft's sensor systems and manipulators. In the
Internet world, we use standards called the TCP/IP protocol suite--packet
switching and store-and-forward methods--to allow a lot of different devices,
billions of things, to interact compatibly with each other. The team set out
to develop a suite of protocols that would allow us to have the kind of
network flexibility in space that we have on Earth. The Interplanetary
Internet project is primarily about developing a set of communication
standards and technical specifications to support rich networking in space
environments.

TR:What are the challenges of building such a network in space?

VC:We started by working on a set of protocols that could deal with two very
important properties of space communication. The first is delay. The
distances between the planets are very large. For example, when Earth and
Mars are closest together, it still takes 3.5 minutes for a radio signal
moving at the speed of light to propagate. If I were on Mars and you were on
Earth, it would take seven minutes at best before you heard a response. When
Earth and Mars are farthest apart, the round trip takes 40 minutes! The
reason we can talk back and forth on Earth so easily is that propagation
times are very short by comparison.

The other problem is that the planets and their satellites are in motion, and
most are rotating. The rotation of the planets means that if you are talking
to something that is on the surface of the planet, it may rotate out of the
line of sight so you cannot talk to it anymore, until the device on the
surface rotates into view again. The same could be said for some orbiting
satellites. You have to develop protocols that will deal with the fact that
you cannot always communicate with the other party: the communication is both
delayed and potentially disrupted. So that is what we designed: a delay- and
disruption-tolerant networking system [DTN]. It will allow us to maintain
communications more effectively, getting much more data because we don't have
to be in direct line of sight with the ultimate recipient in order to
transfer data. The new protocols will be proposed to serve as a potential
international standard for space networking.

TR:How does this new protocol, the delay- and disruption-tolerant networking
system, work?

VC: We are using store-and-forward methods [routing information through hosts
that hold on to it until a communications link can be established] similar to
the TCP/IP design in order to service space-communication requirements. But
our new bundle protocol is based on DTN principles. We have to cope with the
fact that there is a really high potential for delay and disruption in the
system. For example, Pluto is a long ways away, on the order of three to five
billion miles and about 12 hours round-trip time. Using the DTN bundle
protocol allows us to design more-complex mission configurations involving
many devices on the surface of planets and in orbit around them. At Mars, for
example, there are four orbiters and three landed and operational spacecraft.
We expect to be able to use the standard TCP/IP protocols on the surface of
planets and inside spacecraft, but we will use the DTN protocols for
interplanetary distance communications.

TR: Is this going to require putting new infrastructure in space?

VC: The answer is yes and no. For example, the Deep Impact spacecraft [now
called EPOXI] is already in orbit around the sun. It was used to launch a
probe into a comet to examine its interior. EPOXI is being temporarily
repurposed to test the new DTN protocols. The spacecraft has processing,
memory, radio equipment, and solar panels for power so we don't have to put
new hardware up. We just have to upload new software. We are lucky to not
have to field any new equipment yet, but the DTN protocols eventually have to
show up in a fairly significant number of devices in the system to create the
kind of network that can serve space-communication needs. Some specialized
spacecraft could become store-and-forward routers. Each time a new mission is
launched, using the standard bundle protocol, previous mission assets that
are still in operation could be used to support the communication
requirements of the new mission. In this way, we hope to accrete a kind of
interplanetary backbone network.

TR: How are you handling security issues?

VC: There are security concerns, and we have been very careful to build
defenses into the basic design. Each bundle-aware node will verify the
identity of any other nodes that it is communicating with, and it will refuse
to forward data from any nodes that it does not recognize. We will be using
strong authentication methods, cryptographic communication methods, to ensure
that the parties that are using the resources are authorized to do so.

TR: What is the biggest advantage of building new protocols for space
communication?

VC: The important part here is that we have standardized protocols that will
allow internetworking of various spacecraft launched by all the spacefaring
nations. Over time, as new missions are launched, you start to build up a
backbone capability. Every time you put up a new mission, you basically are
putting up another potential node in the network. Our hope in the near term
is to start putting DTN/bundle-protocol applications up on the Internet
terrestrially, and also put them up on the International Space Station for
testing. Eventually, we hope to have this capability running all the time,
and then, when new deep-space missions are launched using these standard
protocols, they will become part of the interplanetary communications system.

Copyright Technology Review 2008.