The Lunar Space Communications Architecture: Beyond the NASA–KARI Study

During October 2014–April 2015, the Korea Aerospace Research Institute (KARI) and the National Aeronautics and Space Administration (NASA) conducted a feasibility study for the purpose of identifying potential areas of cooperation in lunar robotic exploration activities. A key objective of the joint study was to define a space communications architecture that will serve as a framework for accommodating the communications and navigation capabilities and services provided by NASA’s Deep Space Network (DSN); the Korea DSN (KDSN), a potential lunar relay; the Korea Pathfinder Lunar Orbiter (KPLO); and the KPLO Mission Operations System (MOS). This lunar communications architecture is intended to support, in addition to the KPLO mission (to be launched in 2018), other lunar potential missions, i.e., NASA or KARI lunar CubeSat missions and a NASA Resource Prospector mission, to be operational in the 2018–2021 time frame. A salient feature of this architecture is the service paradigm propagated from that of the DSN. Both DSN and KDSN will operate on a multi-mission basis, serving multiple flight missions concurrently. They execute a set of standard services through Consultative Committee on Space Data Standard (CCSDS)-compliant standard protocols to communicate with the spacecraft of the user missions over the space-ground communications link and CCSDS-compliant standard interfaces with the MOS over the ground-to-ground link. In other words, they are interoperable to each other, and from the viewpoint of the user missions of KARI and NASA, they can obtain “cross support” by the network assets of the two agencies. The second feature of the lunar space communications architecture is the existence of a prototypical lunar network, enabled by the lunar relay asset. This is a new type of communications asset in the lunar region. Three different relay configurations, i.e., the integrated relay payload, the hosted relay payload, and the independent relay satellite, were assessed for their feasibility, functionality, and performance. Another feature is the multiplicity of the communications links, i.e., trunk link, in situ link, and direct to/from Earth (DTE/DFE) links, and their associated complexity due to the diversity of user missions, e.g., multiple frequency bands (X-, S-, and UHF-bands) to be supported by the radios in the system architecture.