The Sea and Land Surface Temperature Radiometer (SLSTR) Detection Assembly design and performance

The SLSTRs are high accuracy radiometers selected for the GMES mission Sentinel-3 space component to provide SST data continuity respect to previous (A) ATSRs for climatology. Many satellites, each with 7.5-year lifetime, over a 20-year period are foreseen. Sentinel-3A will be launched in 2014 and Sentinel-3B at least 6 months later implying that two identical satellites will be maintained in the same orbit with 180 degrees phase delay. Each SLSTR has an improved design respect to AATSR affording large near nadir and oblique view swaths (1400 and 740 km) for SST/LST global coverage at 1 km spatial resolution with a daily revisit time (with two satellites), appropriate for climate and meteorology. Clouds screening and other products are obtained with 0.5 Km spatial resolution in visible and SWIR bands while two additional channels are included to monitor high temperature events, such as forest fires. The two swaths are obtained with two conical scans and telescopes combined optically at a common focus, representing the input of a cooled Focal Plane Assembly, where nine channels are separated with dichroic and focalized on detectors with appropriate optical relays. IR and SWIR optics/detectors are cooled to 85 K by an active mechanical cryo-cooler with vibration compensation, while the VIS ones are maintained at a stable temperature. The opto-mechanical design and the expected electro-optical performance of the Focal Plane Assembly are described and the models predictions at system level are compared with experimental data acquired in the vacuum chamber in flight representative thermal conditions or in laboratory.