The objectives of this activity are:
Targeted Improvements:Improved knowledge of the optical link availability for selected optical ground station locations and validation of long term optical link availability prediction methods.
Description:Accurate knowledge ofthe optical link availability between a spacecraft and optical ground stations is of paramount importance for assessing the feasibility of optical communications through the atmosphere for future telecommunication mission scenarios (e.g., optical feeder links forbroadband access/multimedia applications, optical feeder link for data relay services). The major contributor to optical link unavailability is cloud blockage. Detrimental effects due to propagation through the turbulent atmosphere can additionally decrease the optical link availability. In order to make accurate predictions of link availability it is necessary to have precise information on local cloud coverage and atmospheric characteristics.
In the frame of a GSP study (ONUBLA, Contract No 4000110718), optical link availability has been assessed based on cloud imagery data sets from several geostationary and low earth orbit satellites over a period of five years. However, the accuracy of using such cloud images to predict long term optical link availability is unknown and needs to be quantified by comparison with long term measurement of the local atmospheric conditions.
This activity entails the design,manufacture, installation and operation of the necessary equipment (e.g., wide field cloud-monitoring cameras, turbulence profile monitoring equipment, laser link transceivers) to measure the local atmospheric conditions at selected ground locations in Europe andin its vicinity (e.g., Middle East and Africa) over an extended period of time. The use of image processing techniques is envisagedto extract cloud and atmospheric turbulence information from images of the local cloud cover taken from the ground (e.g., cloud type, altitude, physical properties, cloud temporal evolution, Cn2 parameter, Fried parameter temporal evolution, wind profile), together with periodic measurement of the local atmospheric attenuation at a relevant laser wavelength.
The local measurement results willbe correlated with cloud imagery data sets available from other sources (e.g., MSG, MODIS, local meteorological sites) for the sametime period to determine the accuracy of using these available cloud imagery data sets to forecast the optical link availability over longer time periods.