For several years, CILAS has developed an expertise in the field of optical thin films deposition and in-situ visible and infrared optical monitoring techniques that enables us today to successfully answer such increasingly request of space systems for Earth observation and Climate monitoring. In particular, Dual Ion Beam Sputtering technology (DIBS) and Plasma Ion Assisted Deposition (PIAD) allow us to guarantee the production of coatings that are nearly insensitive to temperature and atmospheric conditions. We first present the results of the manufacturing of the high performances optical coatings for Microcarb Instrument. MicroCarb is designed to map sources and sinks of carbon dioxide (CO2), the most important greenhouse gas, on a global scale. The instrument on board MicroCarb is an infrared passive spectrometer operating in four wavelengths using an echelle grating to achieve spectral dispersion. In this paper, we present also the manufacturing results of a dichroic beamsplitter dedicated to Earth observation, which has been designed to transmit light in the [800-900nm] spectral range, whereas reflecting the [450-700nm] spectral range for 45° angle of incidence. The front face involves multidielectric coating structures based on high-pass functions. The rear face requires an antireflection coating in the [800-900nm] spectral range, designed to compensate the bending induced by the front face coating in order to reach the flatness requirements of 10 nm rms.
Ariel (Atmospheric Remote-Sensing Infrared Exoplanet Large Survey) has been adopted as the M4 mission for ESA “Cosmic Vision” program. Launch is scheduled for 2029. ARIEL will study exoplanet atmospheres through transit spectroscopy with a 1 m class telescope optimized in the waveband between 1.95 and 7.8 μm and operating in cryogenic conditions in the temperature range 40-50 K. Aluminum alloy 6061, in the T651 temper, was chosen as baseline material for telescope mirror substrates and supporting structures, following a trade-off study. To improve mirrors reflectivity within the operating waveband and to protect the aluminum surface from oxidation, a protected silver coating with space heritage was selected and underwent a qualification campaign during Phase B1 of the mission, with the goal of demonstrating a sufficient level of technology maturity. The qualification campaign consisted of two phases: a first set of durability and environmental tests conducted on a first batch of coated aluminum samples, followed by a set of verification tests performed on a second batch of samples coated alongside a full-size demonstrator of Ariel telescope primary mirror. This study presents the results of the verification tests, consisting of environmental (humidity and temperature cycling) tests and chemical/mechanical (abrasion, adhesion, cleaning) tests performed on the samples, and abrasion tests performed on the demonstrator, by means of visual inspections and reflectivity measurements.
Atmospheric Remote-Sensing Infrared Exoplanet Large Survey (Ariel) has been adopted as ESA “Cosmic Vision” M4 mission, with launch scheduled for 2029. Ariel is based on a 1 m class telescope optimized for spectroscopy in the waveband between 1.95 and 7.8 μm, operating in cryogenic conditions in the range 40–50 K. Aluminum has been chosen as baseline material for the telescope mirrors substrate, with a metallic coating to enhance reflectivity and protect from oxidation and corrosion. As part of Phase B1, leading to SRR and eventually mission adoption, a protected silver coating with space heritage has been selected and will undergo a qualification process. A fundamental part of this process is assuring the integrity of the coating layer and performance compliance in terms of reflectivity at the telescope operating temperature. To this purpose, a set of flat sample disks have been cut and polished from the same baseline aluminum alloy as the telescope mirror substrates, and the selected protected silver coating has been applied to them by magnetron sputtering. The disks have then been subjected to a series of cryogenic temperature cycles to assess coating performance stability. This study presents the results of visual inspection, reflectivity measurements and atomic force microscopy (AFM) on the sample disks before and after the cryogenic cycles.
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