Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/01/2015 Terms of Use: http://spiedl.org/terms . #%'## #" "(/ (0 #-'( #))%"!!#"With a data rate of 5.6 Gbps the laser communication links reported here have been a milestone in the introduction of laser communication terminals to the space market. For the first time the major advantage of laser communication terminals compared to RF payloads -data rates larger than 1 Gbps -has been demonstrated on orbit. In terms of shortterm service realization the most imminent market applications are relay services (LEO-to-GEO-to-ground) to make the large data amount of LEO Earth observation satellites immediately available. DLR plans to utilize the laser communication capabilities for the TanDEM-X mission and took TESAT under contract to adapt the now successfully proven LEO-LEO laser communication terminals to LEO-to-GEO, GEO-GEO, and GEO-to-ground links. This GEOclass LCT is designed for up to 45,000 km distance at a maximum user data rate of 1.8 Gbps.The next figure (Fig. 8) shows the application for which TESAT has developed and currently builds laser communication terminals and a 600 Mbps Ka-band subsystem.
A free-space optical link based on homodyne BPSK (binary phase shift keying) has been established between two of the Canary islands, La Palma and Tenerife, to transmit 5.625 Gpbs across 142 km. This link verifies homodyne BPSK as a robust modulation scheme even for the transmission through the atmosphere.
Laser communication terminals based on homodyne BPSK are under in-orbit verification in LEO-to-ground and duplex LEO-LEO 5.65 Gbps links. With the LEO-to-ground link beacon-less acquisition has been verified as a reliable and quick acquisition procedure with acquisition times less than one minute.
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