Free space communications between ground stations and geostationary satellites offer high-speed and secure data transmission, but compensating for atmospheric absorption poses a significant challenge. The need for high levels of beam power to overcome atmospheric losses calls for optics that can withstand strong flux, especially in the continuous wave (CW) regime. In this context, the absorption of optics at 1.5 µm is a critical parameter that must be accurately measured and understood to develop efficient and reliable photonic systems. This study focuses on the absorption of optical coatings at 1570 nm. Lock-In Thermography (LIT) has been developed to measure the total absorption of the coatings with high sensitivity under 1 ppm. A modulated 100 W CW laser is used to induce heating into the coating stack, and the resulting rise in internal temperature is measured with a thermal camera. The LIT experimental setup offers a non-destructive and non-contact measurement technique, making it ideal for assessing the absorption of delicate thin-film coatings. To understand the photo induced effects in a stack of thin film layers subjected to high-power laser heating, a finite element model is developed using COMSOL. The model simulates the index and thickness variations of each layer and predicts the shift in optical function resulting from photo induced effects. The results offer valuable insights into the impact of laser-induced heating on the optical properties of the coatings and provide guidelines for designing robust and reliable photonic systems.
The Copernicus Land Surface Temperature Monitoring (LSTM) mission is part of the Copernicus Sentinel Expansion Missions. It will carry a high spatial-temporal resolution thermal infrared sensor to provide observations of the land-surface temperature. The mission responds to priority requirements of the agricultural user community for improving sustainable monitoring requirements to better manage water resources and learn about yield, vegetation and crop growth. The spectral coverage in the multiple bands spans from 490nm to 1610nm for the VNIR/SWIR part of the instrument. Materion Optics Balzers was selected as responsible supplier for the VNIR/SWIR filter assemblies. This contribution addresses the design, manufacturing and characterization of the demanding dielectric optical coatings for the sophisticated band pass filters and dichroic by PARMS technology for the LSTM project by Materion Optics Balzers.
Matthias Mohaupt, Christian Scheffler, Falk Kemper, Gerd Harnisch, Max Henning, Andreas Rahm, Olivier Sengenès, Bruno Badoil, Pierre-Olivier Antoine, Emilie STeck
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.
KEYWORDS: Equipment, Signal to noise ratio, Calibration, Short wave infrared radiation, Modulation transfer functions, Design and modelling, Astronomical imaging, Thermography, Tunable filters, Telescopes
The Land Surface Temperature Monitoring (LSTM), part of the expansion missions of the Copernicus programme, aims at providing data for land surface temperature and evapotranspiration at unprecedented spatio-temporal resolution, with the main objective of providing valuable data for improved water management at individual European field scale. This paper gives an overview of the instrument main requirements flowing down from the mission objectives, and the instrument design selected to fulfill them. The technical challenges are described as well as the preliminary predicted performances.
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The satellite market is shifting towards smaller (micro and nanosatellites), lowered mass and increased performance platforms. Nanosatellites and picosatellites have been used for a number of new, innovative and unique payloads and missions. This trend requires new concepts for a reduced size, a better performance/weight ratio and a reduction of onboard power consumption. In this context, disruptive technologies, such as laser-optical communication systems, are opening new possibilities. This paper presents the C3PO1 system, “advanced Concept for laser uplink/ downlink CommuniCation with sPace Objects”, and the first results of the development of its key technologies. This project targets the design of a communications system that uses a ground-based laser to illuminate a satellite, and a Modulating Retro-Reflector (MRR) to return a beam of light modulated by data to the ground. This enables a downlink, without a laser source on the satellite. This architecture suits well to small satellite applications so as high data rates are potentially provided with very low board mass. C3PO project aims to achieve data rates of 1Gbit/s between LEO satellites and Earth with a communication payload mass of less than 1kilogram. In this paper, results of the initial experiments and demonstration of the key technologies will be shown.
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