LCTs 6 Years Operations: More Than 25.000 Successful Optical Links

Laser Communication Terminals (LCTs) became commercial units and proved the quality and capabilities of optical communications. TESAT's LCTs have successfully accomplished more than 25.000 links in the past six years. In this paper, an overview of the results generated during this time is presented. Eight LCTs 135, 1064 nm wavelength are/have been in operation in the past six years. Two LCTs are on board of geostationary satellites (GEOs) and six are/were on board of low-orbit satellites (LEOs) covering wide range of missions from earth observation (e.g. Copernicus program) and surveillance to technology demonstrator payloads (e.g. TDP1 Experimentation Program) [1] [2]. Space to ground links (SGLs) have been demonstrated using different art of optical ground stations (OGS). Upand down-optical links with and without communication between the Technology Demonstrator Payload 1 (TDP1) and the DLR Transportable Adaptive Optics Ground Station (T-AOGS) [12] have been used for experimental purpose, contributing to the data generation for atmospheric modelling and supporting the experts in building a better understanding of atmospheric impact onto the optical channel [3]. In order to implement and operate the LCTs, new operational concepts have been developed. Generation of operational products like link requests or commanding files has been supported and tuned [5] [2]. Further technology applications like airborne terminals are currently under validation. In 2019, several companies have started the verification of their terminals using the E2E test bed TDP1 and the T-AOGS described in [4]. Testing campaigns are ongoing in 2019. The TDP1 test bed has also supported quantum key distribution (QKD) verifications [7] [13] and optical channel characterization [9]. Methods for analysis, characterization and assessment of trends and performances of the LCTs in space and OGS have been developed and implemented. The Long Term Performance Analysis (LTPA) enables the assessment of potential degradations and allows for an introduction of corresponding counter measures (i.e. parameter settings modifications) preventing from negative impact on operations and services [6] [10]. The knowledge gained from the TDP1 Program has been an important contribution to the Consultative Committee for Space Data Systems (CCSDS). [8].