Four years operations of Inter-satellite and SpaceGround Optical links

During the past four years, the laser communication terminal on board of Alphasat GEO-stationary satellite has achieved the successful execution of more than 1300 optical links which implies more than 24.000 tasks for the planning system. This laser terminal in combination with a Ka-Band system constitutes the TDP1 technology demonstrator. Approximately half of the links were inter-satellite optical links, using the Sentinels low orbit satellites of the EU Copernicus program (S1A, S1B, S2A and S2B) as communication partner with the aim of supporting in orbit commissioning activities and TDP1 experimentation purposes. The other half of the links used the transportable adaptive optical ground station of the DLR (T-AOGS [2]) located currently at Tenerife, Spain as counter terminal. These optical satellite to ground links prepare the way not only to GEO feeder links, but also for connecting the space segment to HAPs, airborne terminals or LEO direct to earth links. In contrast to pure inter satellite links the satellite to ground links involve the atmosphere and local weather conditions. Adopting the operational concept established for inter satellite links, a certain percentage of the planned links cannot be conducted (e.g. due to clouds). The conducted links were used to characterizing the T-AOGS, characterize the atmospheric conditions as well as optimize and test coding schemes. Most of the tasks executed by the LCTs and the Ka-Band have been based in the TESAT input delivered to the MCC (operated by DLR GSOC), further processed and finally transferred to the spacecraft control center.