Interplanetary Internet


NASA Launches Project to Blast Internet Into Outer Space
By Greg Clark

3 December 1999

It doesn't take a crazy leap of imagination to consider the
solar system sprinkled with astronauts in the coming century.
There may be a permanent base on the moon, mining projects in
the asteroid belt, a fledgling colony on Mars, and exploratory
robotic spacecraft probing Venus, Pluto and the moons of
Saturn and Jupiter.

An unanswered question is how will all these pioneering
outposts communicate with each other and with folks back home
on Earth. The complications are many. Each station will be
whizzing around the solar system at different speeds in
different orbits, separated by distances that take radio
signals anywhere from a few seconds to tens of hours to cross.
Sometimes the points are close, as when Earth laps Mars in its
orbit around the sun, other times the two planets are at
opposite sides of the solar system separated by hundreds of
millions of miles and a giant fiery star.

Until now NASA missions have always set up radio and, in some
cases, television communications mission by mission. A future
where human projects populate the solar system, though, will
require much more intricate and full-service infrastructures.

Enter the Interplanetary Internet -- a futuristic web of radio-
linked computer networks deployed across the solar system.
Earlier this month NASA's Jet Propulsion Laboratory embarked
on a project to devise standards for the Interplanetary
Internet. The plan will essentially take small pieces of the
Internet as it exists on Earth and deploy them throughout the
solar system, linking them together through gateways, which
may be orbiting satellites that function somewhat like

The project is being funded by NASA and the Defense Advanced
Research Projects Agency, the group that in the 1960s
pioneered the development of the Internet. Managed by JPL, the
project will incorporate the knowledge of scientists and
engineers from universities, government agencies and private
industry. Vinton Cerf, the computer scientist often called the
"father of the Internet," for his role in developing the
TCP/IP protocol that governs Internet communications, is
playing a key role.

The protocol is the method computers use to talk with each
other. The Interplanetary Internet will require a new protocol
that overcomes several problems unique to transmitting radio
signals through long distances in space, said Adrian Hooke,
manager of NASA's Space Mission Operations Standarization
Program. Hooke plays a leading role in the Interplanetary
Internet project.
"Most protocols on the Internet operate in a mode where you
essentially send a bunch of data and then you wait for an
acknowledgement that those data got there, then if they didn't
get there you back up and retransmit them," Hooke explained.
Transmitting over the huge distances of space, this method of
communicating becomes completely inappropriate, because the
radio signals take so long to travel from point to point. "You
end up in a stacatto mode of operating," Hooke said.

In addition to the long time delay in space, other basic
problems that make the current internet protocol inappropriate
for interplanetary communications are the high noise of radio
transmissions, and the fact that continuous connections are
impossible in space.

Even a spacecraft orbiting Earth has to use several radio relay
stations to keep in contact with mission control. For a
scientist in a space station on the moon to maintain contact
with a spacecraft orbiting Jupiter would be even more
difficult. At one moment the call might need to be relayed
through a station on Mercury, and an hour later It might pass
through a gateway in Mars orbit.

The entire network would be a very complex web of relay

"It's kind of like one of those cat's cradle elastic-band
things," Hooke said. "Everything's moving. All these links are
coming and going and seeing each other and getting obscured,
and somehow you want to be able to simplify out of that a
reliable communications backbone. That is a humongous job in
terms of scheduling and modeling and planning how those links
become available."

While a great deal of research must be done on the subject of
routing signals through the solar system, many of the
technologies being developed on Earth already address some of
the communications challenges, Hooke said. For instance,
sending e-mail from a laptop computer in a moving car, through
a cellular phone network to a hard-wired personal computer is
similar to the trouble of communicating with a moving

What the new JPL project is trying to do is to take the
technologies that are emerging for wireless and satellite
communications on Earth and move them off the planet. The task
is to organize various research groups to develop standardized
procedures and protocols that will make the Internet work in
space, Hooke said. It requires detailed cooperation between the
space communications community and the groups that set
standards for Internet communications.

Eventually, Hooke envisions robotic rovers on Mars, surface
landers, orbiting satellites, high altitude balloons and even
exploratory aircraft to be able to exchange information and
communicate with all engaged in scientific studies, will be
able to communicate with human controllers on Mars and back on