Surrey Satellite Technology Ltd (SSTL) can boast ‘a first’ now that the first use of the ‘bundle’ protocol in space has been demonstrated with their UK-DMC satellite. Sensor data was successfully delivered from the satellite using this disruption- and delay-tolerant networking protocol designed for the Interplanetary Internet.
Wireless ad-hoc communication networks and networks operating in extreme environments suffer frequent outages and disruption, and require careful engineering to meet their needs. Spacecraft and probes operating beyond Earth orbit have intermittent communication contact limited by orbital dynamics. These space communication links create worst-case scenarios for disruption and long communication outages. Delay-Tolerant Networking techniques address these issues for systems that lack continuous network connectivity. The ‘bundle’ protocol has been developed in a co-operative research effort to support continuous communications across disrupted links.
The UK-DMC satellite has delivered delay-tolerant networking ‘bundles‘ carrying remote-sensing image data to NASA Glenn Research Center in Cleveland, Ohio, via SSTL’s Guildford, England, Mission Control Centre. The first complete image, of South Africa’s Cape of Good Hope, was downloaded in fragments across two separate satellite passes to a ‘bundle agent’ in SSTL’s ground station. The fragments were then sent across the Internet to NASA Glenn‘s agent, and reassembled into the image file. That file was then delivered back to SSTL for post-processing and orthorectification.
Proactive bundle fragmentation protects against the disruption and link outage that occurs between the two separate satellite passes over the ground station. SSTL’s high-performance Saratoga protocol enabled the bundles to be transferred quickly and effectively to the ground.
The UK-DMC satellite is a member of the Disaster Monitoring Constellation (DMC), used for observing the Earth for major disasters and commercial land monitoring. Currently there are four DMC satellites in daily use in orbit that rely on standard Internet Protocol (IP) networking to send mission-critical imagery to ground stations and to interact with terrestrial networks. The DMC effectively extends the Internet to orbit, and its farsighted adoption of IP has made it possible to take the backbone of the Internet even further into space. Networking technologies new to the space environment, such as the bundle protocol and the Cisco Systems Internet router onboard the UK-DMC satellite, can be experimented with and evaluated for further use.
Working together and using Internet technology to prototype the future Interplanetary Internet, NASA Glenn Research Center, SSTL and Cisco Systems are the first to evaluate the delay-tolerant networking bundle protocol in space. This work will be publicly presented on September 30 at the 59th International Astronautical Congress 2008 in Glasgow, where SSTL will also be exhibiting.
