Satellite-based quantum communication terminal employing state-of-the-art technology
Feature Issue on Optical Wireless Communications (OWC) We investigate the design and the accommodation of a quantum communication transceiver in an existing classical optical communication terminal on board a satellite. Operation from a low earth orbit (LEO) platform (e.g., the International Space Station) would allow transmission of single photons and pairs of entangled photons to ground stations and hence permit quantum communication applications such as quantum cryptography on a global scale. Integration of a source generating entangled photon pairs and single-photon detection into existing optical terminal designs is feasible. Even more, major subunits of the classical terminals such as those for pointing, acquisition, and tracking as well as those providing the required electronic, thermal, and structural backbone can be adapted so as to meet the quantum communication terminal needs.
TESAT laser communication terminal performance results on 5.6Gbit coherent inter satellite and satellite to ground links
The increasing demand on high speed communication networks has stimulated the development of optical free space data transmission during the last years. TESAT has developed a laser communication terminal (LCT) that fulfills the need of a power efficient system whose capability has been successfully demonstrated at bidirectional space-to-space links and bidirectional space-to-ground links (SGLs) at a data rate of 5.625 GBit/s with a homodyne detection scheme and a BPSK modulation format. In comparison to a direct detection system, the homodyne detection scheme works as a bandpass filter. The transmission is immune to false light and even data transmission with the sun in the receiver field of view (FOV) is possible. Compared to common RF transmission which is implemented on spacecrafts for data transmission, optical transmission provides not only higher transmission rates (factor 10) but also shows excellent security features since the laser beams directivity making it immune to interception.
Analysis of the preliminary optical links between ARTEMIS and the Optical Ground Station
In the frame of the SILEX project, the European Space Agency (ESA) has put into orbit two Laser Communication Terminals, to establish an experimental free space optical communication link between a GEO satellite (ARTEMIS) and a LEO satellite (SPOT IV), to relay earth observation data. In order to perform In Orbit Testing (IOT) of these, and other, optical communications systems, ESA and the Instituto de Astrofisica de Canarias (IAC) reached an agreement for building the Optical Ground Station (OGS), in the Teide Observatory of the IAC. With ARTEMIS placed in a circular parking orbit at about 31000 kilometres, its optical payload has been preliminary tested with the OGS. First results and analysis are presented on the space-to-ground bi-directional link, including pointing acquisition and tracking performance, Bit-Error Rate (BER) and transmitted beam divergence effects related with atmospheric models and predictions. Future plans include deeper optical bi-directional communication tests of OGS, not only with ARTEMIS but also with OSCAR-40 (downlink) and SMART-1 (up-link) satellites, in order to do a full characterisation of the performances of laser beam propagation through atmospheric turbulence and a comparison with theoretical predictions.
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