A Fourier transform spectroradiometer for ground-based remote sensing of the atmospheric downwelling long-wave radiance

Abstract

Abstract. The Radiation Explorer in the Far Infrared – Prototype for Applications and Development (REFIR-PAD) is a Fourier transform spectroradiometer that has been designed to operate from both stratospheric balloon platforms and the ground. It has been successfully deployed in a stratospheric balloon flight and several ground-based campaigns from high-altitude sites, including the current installation at the Italian–French Concordia Antarctic station. The instrument is capable of operating autonomously with only a limited need of remote control and monitoring and provides a multiyear dataset of spectrally resolved atmospheric downwelling radiances, measured in the 100–1500 cm−1 spectral range with 0.4 cm−1 resolution and a radiometric uncertainty of better than 0.85 mW(m2srcm-1)-1.

Observations of the downwelling far-infrared atmospheric emission at the Zugspitze observatory

“…The emission spectrum was measured in the FIR with FIR-MOS, which was developed at CNR-INO with the support of ESA and the Italian Space Agency (ASI) and installed in November 2018 on the terrace of the Summit station. The instrument is a Fourier transform spectrometer (FTS) designed on the base of a similar instrument, named Radiation Explorer in the Far InfraRed -Prototype for Applications and Development (REFIR-PAD) (Bianchini et al, 2019), permanently installed in Antarctica in 2012 (Palchetti et al, 2015). The FTS consists of an interferometric layout with doubleinput and double-output ports in a Mach-Zehnder configuration, which increases the measurement reliability and the calibration precision (Carli et al, 1999).…”

“…Spectra are provided without apodisation, with a sampling resolution corresponding to the sinc response function of σ = 0.3 cm −1 for FIRMOS (maximum optical path difference (MOPD) = 1.66667 cm) and σ = 0.48215 cm −1 for E-AERI (MOPD = 1.03703 cm). The instrument line shape (ILS) of FIRMOS is a linear combination of sinc and sinc 2 (as in the case shown in Bianchini et al, 2019) with a full width at half maximum (FWHM) of about 0.36 cm −1 , whereas for E-AERI the ILS is an "ideal" sinc with FWHM = 0.58 cm −1 (Knuteson et al, 2004). More information about ILSs is provided with the dataset.…”

Comment on essd-2020-377

“…The emission spectrum was measured in the FIR with FIRMOS, which was developed at CNR-INO with the support of ESA, and installed in November 2018 on the terrace of the Summit station. The instrument is a Fourier Transform Spectrometer (FTS) designed on the base of the heritage of a similar instrument, named Radiation Explorer in the Far InfraRed -Prototype for Applications and Development (REFIR-PAD) (Bianchini et al, 2019), permanently installed in Antarctica since 2012 (Palchetti et al, 2015). The FTS consists in an interferometric layout with double-input and double-output ports in a Mach-Zehnder configuration, which increases the measurement reliability and the calibration precision (Carli et al, 1999).…”

Comparison of mid-latitude single and mixed-phase cloud optical depth from co-located infrared spectrometer and backscatter LiDAR measurements

“…The Instrument Line Shape (ILS) of the FIRMOS spectroradiometer is also fitted, in the same way as done with the REFIR-PAD spectroradiometer operating in Antarctica at Dome-C (Palchetti et al, 2015;Bianchini et al, 2019), as a linear combination of a sinc function, which generally contributes with more than 90 %, and a sinc 2 function, which allows to take into account the self-apodization due to the finite internal solid angle Ω of the instrument. The resulting ILS is expressed as follows:…”

“…where ∆ν is the spectral resolution (equal to 0.3 cm −1 ) and ν represents the wavenumber. The α coefficient depends on Ω as shown in Bianchini et al (2019). Ω is also fitted together with a frequency scale shift β, which takes into account both the shift due to the finite aperture given by ν(1 − Ω 4π ) (Davis et al, 2001), and the effect due to the instability of the reference laser, as follows (Palchetti et al, 2016):…”