Novel uncooled infrared detectors

Despite successful commercialization of uncooled microbolometers suitable for imaging, the community is still searching for a platform for imagers that combine affordability, convenience of operation, and excellent performance. More recently, a new type of uncooled detectors based on expansion phenomena in micromechanical structures has been introduced. These detectors are essentially free of intrinsic electronic noise and can be combined with a number of different readout techniques including: capacitive, piezoresistive, electron tunnelling, and optical. In this paper, their design structures and performance are discussed in more detail.

Measurement of the water vapour vertical profile and of the Earth's outgoing far infrared flux

Our understanding of global warming depends on the accuracy with which the atmospheric components that modulate the Earth's radiation budget are known. Many uncertainties still exist as regards the radiative effect of water in the different spectral regions, among which is the far infrared, where very few observations have been made. An assessment is shown of the atmospheric outgoing flux obtained from a balloon-borne platform with wideband spectrally-resolved nadir measurements at the top of the atmosphere over the full spectral range, from 100 to 1400 cm−1, made by a Fourier transform spectrometer with uncooled detectors. From these measurements, we retrieved 15 pieces of information regarding water vapour and temperature profiles and surface temperature, with a major improvement in our knowledge of water vapour in the upper troposphere. The retrieved atmospheric state made it possible to calculate the emitted radiance also at frequencies and zenith angles that have not been observed and to determine the outgoing spectral radiation flux. This proves that spectrally resolved observations can be used to derive accurate information on the integrated flux. While the retrieved temperature was in agreement with ECMWF analysis, the retrieved water vapour profile differed significantly; depending on the time and the location, the derived flux in the far infrared (20–600 cm−1) differed by 2–3.5 W/m2 from that calculated using ECMWF. The error with which the far infrared flux is determined by REFIR-PAD is about 0.4 W/m2 and is caused mainly by calibration uncertainties, while detector noise has a negligible effect. This proves that uncooled detectors are adequate for top-of-the-atmosphere radiometry.

Measurement of the water vapour vertical profile and of the Earth's outgoing far infrared flux

Our understanding of global warming depends on the accuracy with which the atmospheric components that modulate the Earth's radiation budget are known. Many uncertainties still exist on the radiative effect of water in the different spectral regions, among which the far infrared where few observations have been made. An assessment is shown of the atmospheric outgoing flux obtained from a balloon-borne platform with wideband spectrally resolved nadir measurements at the top-of-atmosphere over the full spectral range, including the far infrared, from 100 to 1400 cm−1, made by a Fourier transform spectrometer with uncooled detectors. From these measurements, we retrieve 15 pieces of information about water vapour and temperature profiles, and surface temperature, with a precision of 5% for the mean water vapour profile and a major improvement of the upper troposphere-lower stratosphere knowledge. The retrieved atmospheric state makes it possible to calculate the emitted radiance as a function of the zenith angle and to determine the outgoing radiation flux, proving that spectrally resolved observations can be used to derive accurate information on the integrated flux. While the retrieved temperature is in good agreement with ECMWF analysis, the retrieved water vapour profile differs significantly, and, depending on time and location, the derived flux differs in the far infrared (0–600 cm−1) from that derived from ECMWF by 2–3.5 W/m2±0.4 W/m2. The observed discrepancy is larger than current estimates of radiative forcing due to CO2 increases since pre-industrial time. The error with which the flux is determined is caused mainly by calibration uncertainties while detector noise has a negligible effect, proving that uncooled detectors are adequate for top of the atmosphere radiometry.