European Data Relay System Research Articles

ESA Dual-Standard S-band Transponder: A versatile TT&C equipment for communications via a data relay satellite or directly with the ground network

This paper describes the new ESA Dual-Standard S-band Transponder designed for users of the European Data Relay System (DRS). Two contracts were placed with European companies for the design and development of an elegant breadboard of this equipment on the basis of Hermes spaceplane communication needs. They were completed by the end of 1991. The equipment can be operated in either of two modulation modes: the standard mode allows for direct interface with the existing ground networks whereas the spread spectrum mode is dedicated to operations with Data Relay Satellite Systems. The Dual-Standard Transponder offers new facilities to the user, such as frequency channel programmability, which allows to tune the equipment anywhere within the 2 GHz space research band, or telecommand data rate flexibility. The challenging Hermes requirements justified by the fact that all communication links with the ground are ensured by this equipment lead to a rather complex design. However, thanks to its modular concept, descoped versions can be easily derived to meet the needs of less demanding unmanned spacecraft.

In‐orbit demonstration of optical IOL/ISL—the silex project

AbstractThe use of optical communications for the high‐data‐rate links of the future European Data Relay System (EDRS) is receiving much attention. To confirm the feasibility of such communications links, an experimental system (SILEX) consisting of three satellites (two in geostationary orbit and one in low earth orbit) is planned for 1992 or 1993 to demonstrate both inter‐orbit link (IOL) and intersatellite link (ISL) capabilities. A detailed feasibility study was performed from January to July 1987 under a European Space Agency (ESA) contract with Matra (France) as prime contractor, ANT (West Germany), Telespazio and Selenia Spazio (Italy) as subcontractors, and contributions from Berlin (France) and Dornier (West Germany). The system is based on GaAlAs semiconductor technology (0.8 μm) with silicon avalanche photodiodes (APDs) as detectors and arrays of charge‐coupled devices (CCDs) for both acquisition and tracking sensors. The design will allow wavelength division multiplexing (WDM) and high‐data‐rate transmission to be demonstrated. The expected data rates are 120 Mb/s duplex for ISL, 1 Mb/s on the IOL forward link (GEO→LEO) and two to four simultaneous 60 or 120 Mb/s channels on the IOL return link (LEO→GEO).