Manufacturing, assembly, integration and test of filter assemblies for the LSTM Instrument

The Copernicus Land Surface Temperature Monitoring (LSTM) mission carries a high spatial-temporal resolution thermal infrared sensor to provide observations of land-surface temperature. The mission responds to priority requirements of the agricultural user community for improving sustainable agricultural productivity at field-scale in a world of increasing water scarcity and variability. Land-surface temperature measurements and derived evapotranspiration are key variables to understand and respond to climate variability, manage water resources for agricultural production, predict droughts. It also addresses to land degradation, natural hazards such as fires and volcanoes, coastal and inland water management as well as urban heat island issues [1]. The LSTM instrument design consist of a Thermal Infrared (TIR) detector and a Short Wave Infrared (SWIR) Visible Near Infrared (VNIR) detector. The incoming beam is split into the three channels by two dichroic beam splitter. Each detector is equipped with a filter assembly for spectral band selection. The mechanical design of the SWIR detector plane filter assemblies (DPF-SWIR) was developed by Fraunhofer IOF. A finite elements analysis shows that the design meets all the required mechanical and thermal loads [5]. To prove theoretical analysis, a mechanical model (MM) has been manufactured. The DPF-SWIR MM was designed to be mechanical flight representative. In consequence, optical coatings on the filter stripes and black coatings on the mechanical parts were absent. The assembled mechanical model was characterized by means of mechanical and optical methods. The single filter stripes position and wave front error were key characterization results. The environmental tests of thermal vacuum cycling, sine- and random vibration, and shock caused neither a deviation of these properties nor damage to the assembly. These qualification results were used for TRL 6 acceptance of the developed design, manufacturing, and integration processes.