Evaluation of Deep Space Ka-Band Data Transfer using Radiometeorological Forecasts and Radiometer Measurements

Deep space exploration is aimed at acquiring information about the solar system. In this scenario, telecommunica-tions links between Earth ground receiving stations and extra-terrestrial satellite platforms have to be designed inorder to ensure the optimal transfer of the acquired scientific data back to the Earth. A significant communicationcapacity has to be planned when very large distances, as those characterising deep space links, are involved thusfostering more ambitious scientific mission requirements.At the current state of the art, two microwave channel frequencies are used to perform the deep space datatransfer: X band (∼ 8.4 GHz) and Ka band (∼ 32 GHz) channel.Ka-band transmission can offer an advantage over X-band in terms of antenna performance with the same antennaeffective area and an available data transfer bandwidth (50 times higher at Ka band than X band). However, Earthtroposphere-related impairments can affects the space-to-Earth carrier signals at frequencies higher than 10 GHzby degrading its integrity and thus reducing the deep space channel temporal availability.Such atmospheric impairments, especially in terms of path attenuation, their statistic and the possibility toforecast them in the next 24H at the Earth’s receiving station would allow a more accurate design of the deep spacelink, promoting the mitigation of the detrimental effects on the link availability. To pursue this aim, meteorologicalforecast models and in situ measurements need to be considered in order to characterise the troposphere in termsof signal path attenuation at current and future time.In this work, we want to show how the synergistic use of meteorological forecasts, radiative transfer simu-lations and in situ measurements such as microwave radiometry observations, rain gauges and radiosoundings, canaid the optimisation of a deep space link at Ka band and improve its performance with respect to usual practices.The outcomes of the study are in the framework of the Radio-Meteorological Operations Planner (RMOP) projectpromoted by ESA for supporting the BepiColombo mission to Mercury.More in detail, the methodology used in this work foresees the use of Fifth-Generation Penn State/NCARMesoscale Model (MM5) coupled with an Eddington-like radiative transfer model in order to convert theforecasted meteorological variables into radio-propagation parameters. Thus, in-situ observations from microwaveradiometers are used to validate the weather forecasts in terms of integrated water paths in clear sky whereasradiosoundings and rain gauges will provide a reference for temperature and rain accumulations, respectively.Eventually, the final results will be shown in terms of improvements in the transferred data volume when the RMOP chain is implemented.