Space Internetworking for Small Projects

The CCSDS Recommendations on Telemetry and Telecommand are used by many space projects around the world because they specify efficient, flexible methods for communications between ground systems and onboard instruments. They specify a method for addressing onboard instruments and subsystems, which uses the combination of the Spacecraft Identifier (SCID) and the Application Process Identifier (APID). Onboard instruments and subsystems can be identified with the combination of these identifiers uniquely if each spacecraft is operated independently of other spacecraft. In a constellation of space elements, however, the communications method of the CCSDS Recommendations does not work, and capabilities for internetworking must be introduced. This paper proposes a simple method for space internetworking, which is based on the methods used by the current space projects. The proposed method uses the technique of Packet encapsulation. Packets to be relayed by a relay element are transmitted between the ground and the relay element encapsulated in Packets for the relay element. This method does not require development of a new protocol at all. It can be implemented by just adding a component that encapsulates and decapsulates Packets to current systems, and components developed for current space projects can be reused without any modification. This method can also be used for constellations with several hops and several elements without any modification to the basic concept. I