Identification number: 4000136126/21/NL/SC/hm
Type: European Space Agency Requesting Party Activity
Project duration:
Project admin: Ģirts Ozoliņš, Institute of Solid State Physics, University of Latvia (ISSP UL)
Project scientific lead: Dr. Sergejs Fomins, Institute of Solid State Physics, University of Latvia (ISSP UL)
Total funding:
Summary:
Atmospheric turbulence impacts the downlink GEO/LEO feeder budget. Adaptive Optics (AO) systems are used to compensate the distortion at the received wavefront caused by atmospheric turbulence in FSOC. This compensation allows for an efficient coupling at the end receiver of a FSOC.
The scope of the study was to investigate the feasibility of the phase retrieval Coded Diffraction (CD) WFS adaptive optics system developed in ISSP UL to be applicable for free space optical communication (FSOC) in Satellite-Ground communication systems.
First, theoretical system was developed incorporating two beam replicas and additional diffractive lements to effectively sense the wavefront error. Theoretical system appeared to be sensitive in the large range of turbulence magnitudes > 40 dB and showed to be sensitive up to 250 Zernike modes, with input image of only 128 by 128 pixels. Wirtinger Flow algorithm with specificly adapted with specialized optimisation method and implemented in physical concept.
In practical implementation it appeared that diffractive elements produced by lythography methods are not sufficent to explore the full strength proposed phase retrieval approach. Number of improvement were made and Zernike sensitivity up to 10th mode was reached in physical system. We show the potential performance at number of wavelengths, starting with 660 nm and exploring the performance tp 1064 nm and 1550 nm.
Despite the low performance, number of improvement of the system allowed to gain functionality and provide way forward to new application of phase retrieval methods in wavefront sensing.