Design and Analysis of Filter assemblies for the LSTM Instrument

LSTM, funded by the EU and ESA, is part of Copernicus, the European Union's Earth observation program for global monitoring. It is one of the six new missions, expanding the capabilities of the current Copernicus space component. 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, and to address land degradation, natural hazards such as fires and volcanoes, coastal and inland water management as well as urban heat island issues [1]. The LSTM satellite is designed and build by Airbus DS in Madrid, while the development and production of the advanced technology instrument is carried out by Airbus DS in Toulouse. The detector plane filter (DPF) assemblies for the SWIR and VIS detector and the filter assembly for intermediate plane filters VNIR (IPF-VNIR) are developed, manufactured, integrated, and tested by Fraunhofer IOF. Optic Balzers Jena (OBJ) is the responsible subcontractor for the VNIR/SWIR filter assemblies and will provide the optical filter coatings. The design of filter assemblies for the detector plane filters of SWIR detector (DPF-SWIR) is developed. The filter assemblies consist of a lower frame and upper frame. Four single filter substrates coated with the bandpass filter layers are integrated into the lower frame. The upper and lower mask apertures are integrated into the upper and lower frame. The design of DPF-SWIR filter assemblies was analyzed by finite element (FE) analysis. The mechanical loads of sine and random vibration and shock are calculated. The modal analysis shows the meet of requirements of first eigenfrequency. The mechanical loads of interface imperfections are analyzed. The thermal loads are also analyzed, in combination with interface mechanical loads. In sum 21 load cases are investigated.