Working as part of a NASA-wide team, engineers from NASA's Jet
Propulsion Laboratory in Pasadena, Calif., used software called
Disruption-Tolerant Networking, or DTN, 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," said Adrian Hooke, team lead and manager of space-networking
architecture, technology and standards at NASA Headquarters in
NASA and Vint Cerf, a vice president at Google
Inc., in Mountain View, Calif., partnered 10 years ago to develop this
software protocol. The DTN sends information using a method that
differs from the normal Internet's Transmission-Control
Protocol/Internet Protocol, or TCP/IP, communication suite, which Cerf
The Interplanetary Internet must be robust to
withstand delays, disruptions and disconnections in space. Glitches can
happen when a spacecraft moves behind a planet, or when solar storms
and long communication delays occur. The delay in sending or receiving
data from Mars takes between three-and-a-half to 20 minutes at the
speed of light.
Unlike TCP/IP on Earth, the DTN does not
assume a continuous end-to-end connection. In its design, if a
destination path cannot be found, the data packets are not discarded.
Instead, each network node keeps the information as long as necessary
until it can communicate safely with another node. This
store-and-forward method, similar to basketball players safely passing
the ball to the player nearest the basket means information does not
get lost when no immediate path to the destination exists. Eventually,
the information is delivered to the end user.