High performances PDHT evolution towards Ka-band downlink

In the frame of the Earth Observation missions, the on-board Payload Data Handling and Transmission (PDHT) is a fundamental payload aimed to on-board storage of scientific data acquired from embarked payloads (SAR, Optical Payloads, Infrared Payload), their formatting according to CCSDS Recommendations, the modulation, amplification and RF filtering and the data transmission to Ground Segment in X-band. In fact, information rate transmitted to ground has to comply with the narrow allocated transmission X-Band (8025 MHz - 8400 MHz); moreover, in order to achieve an high performance link (low BER) and reduce the transmitted power, Reed-Solomon coding are usually performed, introducing an overhead in the transmitted Transfer Frame thus reducing the spectral efficiency. Actually, the current needs of EO mission already requires high data rate and further evolutions are becoming necessary to cope the future mission needs, as driven by the increase of the payload (SAR, Optical) performances. Having EO planned mission as Sentinels yet achieved the X-Band limits, the Ka-Band (25.5 GHz – 27 GHz) have been selected to cope the future bandwidth needs of higher data rate EO mission as indicated by institutions (ESA, ITU); COSMO 2nd generation is a candidate mission for this shifting, requiring, up to now, a data rate not compatible with the allocated X-Band limits. On the usage of the Ka-Band for EO satellite high downlink data rate, TAS-I is currently conducting, under ESA contract, a study focused on the definition of the entire Ka-Band downlink system, involving on-board consideration (architecture and performance), on-ground (architecture and performances) and at End-to-end level (atmospheric absorption). Some solutions for the Ka-Band downlink system has been identified, according to very demanding system requirement in terms of data rate (2*500 Mbps as a minimum target), data quality and availability of service; the latter is found as one of the most critical requirement, considering the low elevation angles usually experienced in a LEO mission and the attenuation phenomena measured in Ka-Band. The results of the first phase of the study will be presented, including feasibility concepts, HW performances, trade-off between coding and modulation schemes (standard or advanced), antenna implementation (fixed or steerable).