Abstract: A method and system for maintaining an optimized point ahead angle (?a) between an uplink beam (U0) from a first terminal (10) to a second terminal (20), and a downlink beam (D0) from the second terminal (20) to the first terminal (10). While transmitting data via a transmission channel (Tx) from the first terminal (10) to the second terminal (20), a directional variation (??) is applied to an initial point ahead angle (?0) for emitting the uplink beam (U1,U2) along different point ahead angles (?1,?2). A respective intensity (I1,I2) is determined of a part of the uplink beam (U1,U2), received by the second terminal (20), emitted by the first terminal (10) along a respective point ahead angle (?1, ?2). The initial point ahead angle (?0) is adjusted towards an optimized point ahead angle (?a) based on the respective intensity (I1,I2) as function of the different point ahead angles (?1,?2).

Abstract: A wavefront detector (100) and method for determining a signal wavefront (Ws) of a signal beam (Ls). A beam combiner (11) is configured to combine the signal beam (Ls) with a reference beam (Lr). An image detector (12) comprising an array of photosensitive pixels (12p) is configured to receive and measure an interference pattern (Wrs) of the combined signal and reference beams (Lr+Ls). A reference light source (14) is configured to generate the reference beam (Lr). A feedback controller (20) is configured to receive an interference signal (IB) based on measurement of at least part of the combined signal and reference beams (Lr+Ls), and control generation of the reference beam (Lr) by a feedback loop based on the interference signal (IB).

Abstract: Information encoded in an uplink beam (Lu) is transmitted from transceiver (10) on earth (1) to a communication satellite (20) in orbit. The uplink beam (Lu) travels through an atmosphere (2) there between, wherein a wavefront (Wu) of the uplink beam (Lu) is distorted as a result of its propagation through the atmosphere (2). The transceiver (10) comprises a wavefront sensor (12) to measure a reference distortion (Wr?) of a wavefront (Wr) of a reference beam (Lr). Adaptive optics (11) are used to pre-correct a wavefront (Wu) of the uplink beam (Lu) prior to its transmission based on the measured reference distortion (Wr?). The reference beam (Lr) originates from a guidestar satellite (30) formed by a separate man-made object at a distance (D) from the communication satellite (20) such that the reference beam (Lr) travels through the same part (2a) of the atmosphere (2) as the uplink beam (Lu).

Abstract: A wavefront detector (100) and method for determining a signal wavefront (Ws) of a signal beam (Ls). A beam combiner (11) is configured to combine the signal beam (Ls) with a reference beam (Lr). An image detector (12) comprising an array of photosensitive pixels (12p) is configured to receive and measure an interference pattern (Wrs) of the combined signal and reference beams (Lr+Ls). A reference light source (14) is configured to generate the reference beam (Lr). A feedback controller (20) is configured to receive an interference signal (IB) based on measurement of at least part of the combined signal and reference beams (Lr+Ls), and control generation of the reference beam (Lr) by a feedback loop based on the interference signal (IB).

Abstract: Information encoded in an uplink beam (Lu) is transmitted from transceiver (10) on earth (1) to a communication satellite (20) in orbit. The uplink beam (Lu) travels through an atmosphere (2) there between, wherein a wavefront (Wu) of the uplink beam (Lu) is distorted as a result of its propagation through the atmosphere (2). The transceiver (10) comprises a wavefront sensor (12) to measure a reference distortion (Wr?) of a wavefront (Wr) of a reference beam (Lr). Adaptive optics (11) are used to pre-correct a wavefront (Wu) of the uplink beam (Lu) prior to its transmission based on the measured reference distortion (Wr?). The reference beam (Lr) originates from a guidestar satellite (30) formed by a separate man-made object at a distance (D) from the communication satellite (20) such that the reference beam (Lr) travels through the same part (2a) of the atmosphere (2) as the uplink beam (Lu).