For the next generation of very high throughput communication satellites, free-space optical (FSO) communication between ground stations and geostationary telecommunication satellites is likely to replace conventional RF links. To mitigate atmospheric turbulence, TNO and DLR propose Adaptive Optics (AO) to apply uplink pre-correction. In order to demonstrate the feasibility of AO pre-correction an FSO link has been tested over a 10 km range. This paper shows that AO pre-correction is most advantageous for low point ahead angles (PAAs), as expected. In addition, an optimum AO precorrection performance is found at 16 AO modes for the experimental conditions. For the specific test site, tip-tilt precorrection accounted for 4.5 dB improvement in the link budget. Higher order AO modes accounted for another 1.5 dB improvement in the link budget. From these results it is concluded that AO pre-correction can effectively improve high-throughput optical feeder links.

The anticipated capacity benefit of optical satellite communications has triggered a cascade of technology developments. In this paper, we present three such technologies, namely; i). A cube satellite laser terminal (CubeCAT), ii). A lower Earth orbit satellite optical head (LEOCAT) and iii). A calibration and verification test bench for coarse pointing assemblies, named pointing test bench (PTB). For these technologies, pointing stability and accuracy are central challenges. For i) and ii), we discuss anticipated effects of the thermal and mechanical disturbances that threaten the optical alignment of the system. We furthermore explain the mitigation of these effects through the system design so that a high optical performance can be maintained. For iii), we discuss the mechanical design challenges, in combination with modelling and calibration procedures for the system. Effective dealing with the three of them in turn enables highly accurate mirror orientation and rotation. Design specifications and current status are presented for each system.

TNO and DLR envision optical free-space communication between ground stations and geostationary telecommunication satellites to replace the traditional RF links for the next generation of Very High Throughput Satellites. To mitigate atmospheric turbulence, an Adaptive Optics (AO) system will be used. TNO and DLR are developing breadboards to validate Terabit/s communication links using an AO system. In this paper the breadboard activities and first results of the sub-systems will be presented. Performance of these subsystems will be evaluated for viability of terabit/s optical feeder links.

For the next generation of very high throughput communication satellites, TNO and DLR envision optical free-space communication between ground stations and geostationary telecommunication satellites to replace the traditional RF links. To mitigate atmospheric turbulence, an Adaptive Optics (AO) system will be used to apply uplink pre-correction. OFELIA, an ground terminal breadboard was developed to demonstrate the pre-correction principle over an realistic link. Currently, integration tests have been performed to verify the AO performance. Also a laser link experiment over 10 km distance has already been established, in a scenario relevant to ground-to-satellite links. The paper shows that AO is clearly beneficial for the downlink performance. In addition the first preliminary experimental results of the pre-correction show it is also beneficial for the uplink.

To overcome data rate limitations of RF communication links with satellites, TNO and DLR envision optical free-space communication feeder links for next generation high throughput satellites. This paper provides a feasibility assessment of such links and the technology needed. The main results of the link budget and the turbulence modeling of terabit/s optical links are presented. Based on these parameters, requirements and status of the link-subsystems are discussed, and a roadmap is presented, aimed at achieving terabit per second optical feeder links.