Infrared optical coatings for the EarthCARE Multispectral Imager

Abstract

The Earth Cloud, Aerosol and Radiation Explorer mission (EarthCARE) Multispectral Imager (MSI) is a radiometric instrument designed to provide the imaging of the atmospheric cloud cover and the cloud top surface temperature from a sun-synchronous low Earth orbit. The MSI forms part of a suite of four instruments destined to support the European Space Agency Living Planet mission on-board the EarthCARE satellite payload to be launched in 2016, whose synergy will be used to construct three-dimensional scenes, textures, and temperatures of atmospheric clouds and aerosols. The MSI instrument contains seven channels: four solar channels to measure visible and short-wave infrared wavelengths, and three channels to measure infrared thermal emission. In this paper, we describe the optical layout of the infrared instrument channels, thin-film multilayer designs, the coating deposition method, and the spectral system throughput for the bandpass interference filters, dichroic beam splitters, lenses, and mirror coatings to discriminate wavelengths at 8.8, 10.8, and 12.0 μm. The rationale for the selection of thin-film materials, spectral measurement technique, and environmental testing performance are also presented.

Infrared color-sorting metasurfaces

“…This procedure find utility in various applications, including optical networks [1], spectroscopy [2,3], and microscopy [4]. Arrays of spectral filters with steep roll-offs are commonly employed for this purpose, often resulting in lengthy and bulky catadioptric optical trains [5,6]. Optical metasurfaces, utilizing artificially designed structures with subwavelength dimensions, effectively manipulate electromagnetic fields on smaller scales [7][8][9].…”

“…4 Arrays of spectral filters with steep roll-offs are commonly employed for this purpose, often resulting in lengthy and bulky catadioptric optical trains. 5,6 Optical metasurfaces, utilizing artificially designed structures with subwavelength dimensions, effectively manipulate electromagnetic fields on smaller scales. [7][8][9] This presents a promising platform for developing compact and lightweight optical elements with diverse functionalities, 10,11 including examples such as metalenses, 12,13 beam shaping, [14][15][16] edge detection, [17][18][19][20][21][22] quantitative phase imaging, and more.…”