NASA - National Aeronautics and Space Administration

Space Communications and Navigation (SCaN) has completed successful testing of disruption tolerant networking (DTN) in space. Scientists are comparing DTN to the Internet as it will provide increase the quantity and quality of our space based communication operations.

When you look at your cell phone, there is often a signal strength indicator. When your signal indicator is at full strength, your cell phone works well, your calls go through, and you can enjoy your conversations, photo messages, text messages, and a wide variety of other great applications. However, due to a wide variety of environmental factors or hardware limitations, your phone isn’t operating at full signal strength, and sometimes it has absolutely no signal strength at all. If you are on your phone and your signal strength fades, your call drops - or it has been disrupted. It’s exceedingly frustrating to have disrupted calls on Earth, but when you are trying to send information across the globe, to the moon, and further into outer space, disrupted message transmissions are even more frustrating.

To solve this problem, Space Communications and Navigation (SCaN) has been working to develop what many people are calling the “Space Internet” whose fluid operation is enabled by disruption tolerant network (DTN) technologies. Presently, when you think of the Internet you think of an information network that is always interconnected, or “always on” and has very few delays. By moving the internet to space, these truths become false, very quickly. Planets and satellites orbit, and they are not always aligned in such a fashion that data transmission can occur immediately. The ability to send and receive data is disrupted. Information processing nodes, satellites or ground stations, need to be able to store the data that they receive until they are able to safely send it to the next node in the network.

EPOXI
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DTN Testing is Successful

The first successful test of DTN in space took place on board the EPOXI satellite. In October of 2008, Jet Propulsion Laboratory (JPL) and the University of Maryland collaborated in an effort to use the Deep Space Network twice a week to conduct networking demonstrations. The demonstrations were successful and currently SCaN is planning to test DTN capabilities on a wider variety of spacecraft, including the International Space Station via the SCaN Testbed project.

› DTN News and Publications

Date	Event
October 2012	NASA and the European Space Agency (ESA) successfully used DTN to control a small LEGO robot at the European Space Operations Centre in Darmstadt, Germany from the International Space Station. This experiment simulated a scenario in which an astronaut in a vehicle orbiting a planetary body controls a robotic rover on the planet's surface. › DTN Press Release
October 18, 2008	The Interplanetary Overlay Network (ION) DTN software was successfully uploaded to the EPOXI spacecraft and activated on the backup flight computer and network traffic was observed being sent and received to/from the spacecraft in the Deep Impact Network Experiment (DINET) Operations Center.
October 20, 2008	Images were successfully received at the Jet Propulsion Laboratory via the first instance of an “interplanetary network” from the EPOXI spacecraft located approximately 80 light seconds from Earth. These same images were transmitted to the EPOXI spacecraft about 3 hrs earlier via the same network.
October 22, 2008	During experiment Pass 2, 264046 bytes (5 images) delivered. ~97.6% link utilization.
October 27 & 29, 2008	DINET tracking passes 3 and 4 were conducted. All contacts were completed successfully, with no diagnostic messages reported by the DINET software.
November 3, 2008	During the 5th Deep Space Network tracking pass of the DINET experiment, an additional 35 image files totaling 1,587,420 bytes were delivered via the interplanetary network to image reception software in the DINET Experiment Operations Center.

Disruption Tolerant Networking (DTN) Goals, Demonstration, and Participants

What are SCaN’s Goals as they develop DTN?

• Produce an internationally standardized and off-the-shelf family of interoperable DTN protocols that is ready for space mission use.
• Demonstrate the space flight utility of DTN by several quantifiable, repeatable exercises.

Currently, DTN network demonstrations include NASA and international cooperation.

DTN Demonstration Phasing and Participants
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Real-World flight Demonstrations

• Deep Impact Networking (DINET)
• Consultative Committee for Space Data Systems (CCSDS) standardization

DTN Ground Support Environment

• DTN Experimental Network (DEN)

International Space Station Experiments

• BioNet
• SCaN Testbed
• European Space Agency (ESA) Multi-purpose End-To-End Robotic Operations Network (METERON)
• Japan Aerospace Exploration Agency (JAXA) Data Tracking and Relay Satellite (DTRS)