Laser communications relay demonstration: experiments with delay tolerant networking

The Laser Communications Relay Demonstration (LCRD) is a NASA mission that is presently providing a link be- tween two optical ground stations on Earth and geosyn- chronous orbit; this capability will be extended to include a laser terminal on the International Space Station (ISS). From a practical perspective, LCRD provides a 1Gbps Ethernet link with an anticipated round-trip time of 4 sec- onds. Delay Tolerant Networking (DTN) is being used to transcend LCRDs capabilities from a point-to-point link to true network connectivity. Indeed, integrating the LCRD link into any network, such as one aboard the ISS, adds new hops and paths. In this paper, we detail DTN exper- iments conducted using LCRD to demonstrate how DTN and optical capabilities complement each other to enable the next generation of space communication modalities. We conclude with considerations on using LCRD to con- nect the ISS to the optical ground stations.