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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AIRS is the infrared spectroscopic instrument of ARIEL: Atmospheric Remote‐sensing Infrared Exoplanet Large‐survey mission selected in March 2018 as the Cosmic Vision M4 ESA mission and planned to be launched in 2029 by an Ariane 6 from Kourou toward a large amplitude orbit around L2 for a 4 year mission. Within the scientific payload, AIRS will perform transit spectroscopy of over a 1000 of exoplanets to complete a statistical survey, including gas giants, Neptunes, super-Earths and Earth-size planets around a wide range of host stars. All these collected spectroscopic data will be a major asset to answer the key scientific questions addressed by this mission: what are the exoplanets made of? How do planets and planetary system form? How do planets and their atmospheres evolve over time? The AIRS instrument is based on two independent channels covering the CH0 [1.95-3.90] µm and the CH1 [3.90-7.80] µm wavelength range with prism-based dispersive elements producing spectrum of low resolutions R<100 in CH0 and R<30 in CH1 on two independent detectors. The spectrometer is designed to provide spectrum Nyquist-sampled in both spatial and spectral directions to limit the sensitivity of measurements to the jitter noise and intra pixels pattern during the long (10 hours) transit spectroscopy exposures. A full instrument overview will be presented covering the thermal mechanical design of the instrument functioning in a 60 K cold environment, up to the detection and acquisition chain of both channels based on 2 HgCdTe detectors actively cooled down below 42 K. This overview will present updated information of phase B2 studies in particular with the early manufacturing of prototype for key elements like the optics, focal-plane assembly and read-out electronics as well as the results of testing of the IR detectors up to 8.0 μm cut-off.
We present an overview of the cryogenic system of the next-generation infrared observatory mission SPICA. One of the most critical requirements for the SPICA mission is to cool the whole science equipment, including the 2.5 m telescope, to below 8 K to reduce the thermal background and enable unprecedented sensitivity in the mid- and far-infrared region. Another requirement is to cool focal plane instruments to achieve superior sensitivity. We adopt the combination of effective radiative cooling and mechanical cryocoolers to accomplish the thermal requirements for SPICA. The radiative cooling system, which consists of a series of radiative shields, is designed to accommodate the telescope in the vertical configuration. We present thermal model analysis results that comply with the requirements to cool the telescope and focal plane instruments.
The SAFARI instrument is a far infrared imaging spectrometer that is a core instrument of the SPICA mission. Thanks to the large (3 meter) SPICA cold telescope, the ultra sensitive detectors and a powerful Fourier Transform Spectrometer, this instrument will give access to the faintest light never observed in the 34 μm - 210 μm bandwidth with a high spectral resolution. To achieve this goal, TES detectors, that need to be cooled at a temperature as low as 50 mK, have been chosen. The thermal architecture of the SAFARI focal plane unit (FPU) which fulfils the TES detector thermal requirements is presented. In particular, an original 50 mK cooler concept based on a sorption cooler in series with an adiabatic demagnetization refrigerator will be used. The thermal design of the detector focal plane array (FPA) that uses three temperature stages to limit the loads on the lowest temperature stage, will be also described. The current SAFARI thermal budget estimations are presented and discussed regarding the limited SPICA allocations. Finally, preliminary thermal sensitivity analysis dealing with thermal stability requirements is presented.
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