Radiometric calibration of the in-flight blackbody calibration system of the GLORIA interferometer

GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) is an airborne, imaging, infrared Fourier transform spectrometer that applies the limb-imaging technique to perform trace gas and temperature measurements in the Earth's atmosphere with three-dimensional resolution. To ensure the traceability of these measurements to the International Temperature Scale and thereby to an absolute radiance scale, GLORIA carries an on-board calibration system. Basically, it consists of two identical large-area and high-emissivity infrared radiators, which can be continuously and independently operated at two adjustable temperatures in a range from −50 °C to 0 °C during flight. Here we describe the radiometric and thermometric characterization and calibration of the in-flight calibration system at the Reduced Background Calibration Facility of the Physikalisch-Technische Bundesanstalt. This was performed with a standard uncertainty of less than 110 mK. Extensive investigations of the system concerning its absolute radiation temperature and spectral radiance, its temperature homogeneity and its short- and long-term stability are discussed. The traceability chain of these measurements is presented

Radiometric calibration of the in-flight blackbody calibration system of the GLORIA interferometer

GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) is an airborne, imaging, infrared Fourier transform spectrometer that applies the limb-imaging technique to perform trace gas and temperature measurements in the Earth's atmosphere with three-dimensional resolution. To ensure the traceability of these measurements to the International Temperature Scale and thereby to an absolute radiance scale, GLORIA carries an on-board calibration system. Basically, it consists of two identical large-area and high-emissivity infrared radiators, which can be continuously and independently operated at two adjustable temperatures in a range from −50 °C to 0 °C during flight. Here we describe the radiometric and thermometric characterization and calibration of the in-flight calibration system at the Reduced Background Calibration Facility of the Physikalisch-Technische Bundesanstalt. This was performed with a standard uncertainty of less than 110 mK. Extensive investigations of the system concerning its absolute radiation temperature and spectral radiance, its temperature homogeneity and its short- and long-term stability are discussed. The traceability chain of these measurements is presented

Scattering of Noncommutative Waves and Solitons in a Supersymmetric Chiral Model in 2+1 Dimensions

Interactions of noncommutative waves and solitons in 2+1 dimensions can be analyzed exactly for a supersymmetric and integrable U(n) chiral model extending the Ward model. Using the Moyal-deformed dressing method in an antichiral superspace, we construct explicit time-dependent solutions of its noncommutative field equations by iteratively solving linear equations. The approach is illustrated by presenting scattering configurations for two noncommutative U(2) plane waves and for two noncommutative U(2) solitons as well as by producing a noncommutative U(1) two-soliton bound state.Comment: 1+13 pages; v2: reference added, version published in JHE

The in-flight blackbody calibration system for the GLORIA interferometer on board an airborne research platform

The <b>G</b>imballed <b>L</b>imb <b>O</b>bserver for <b>R</b>adiance <b>I</b>maging of the <b>A</b>tmosphere (GLORIA) is a prototype of an imaging Fourier Transform Spectrometer (FTS) for PREMIER, a former candidate mission for ESA's Earth Explorer 7. GLORIA is deployed on board various research aircraft such as the Russian M55 Geophysica or the German HALO. The instrument provides detailed infrared images of the Upper Troposphere/Lower Stratosphere (UTLS) region, which plays a crucial role in the climate system. GLORIA uses a two-dimensional detector array for infrared limb observations in emission and therefore needs large-area blackbody radiation sources (126 mm × 126 mm) for calibration. <br><br> In order to meet the highly demanding uncertainty requirements for the scientific objectives of the GLORIA missions and due to the sophisticated tomographic evaluation scheme, the spatial distribution of the radiance temperature of the blackbody calibration sources has to be determined with an uncertainty of about 0.1 K. Since GLORIA is exposed to the hostile environment of the UTLS with mutable low temperature and pressure, an in-flight calibration system has to be carefully designed to cope with those adverse circumstances. <br><br> The GLORIA in-flight calibration system consists of two identical weight-optimised high-precision blackbody radiation sources, which are independently stabilised at two different temperatures. The two point calibration is in the range of the observed atmospheric infrared radiance emissions with 10 K below and 30 K above ambient temperature, respectively. Thermo-Electric Coolers are used to control the temperature of the blackbody radiation sources offering the advantage of avoiding cryogens and mechanical coolers. The design and performance of the GLORIA in-flight calibration system is presented. The blackbody calibration sources have been comprehensively characterised for their spatially (full aperture) and spectrally (7 to 13 μm) resolved radiation properties in terms of radiance temperatures traceable to the International Temperature Scale (ITS-90) at the Physikalisch-Technische Bundesanstalt (PTB), the national metrology institute of Germany

A large-area blackbody for in-flight calibration of an infrared interferometer deployed on board a long-duration balloon for stratospheric research

The deployment of the imaging Fourier Transform Spectrometer GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) on board a long-duration balloon for stratospheric research requires a blackbody for in-flight calibration in order to provide traceability to the International Temperature Scale (ITS-90) to ensure comparability with the results of other experiments and over time. GLORIA, which has been deployed onboard various research aircraft such as the Russian M55 Geophysica or the German HALO in the past, shall also be used for detailed atmospheric measurements in the stratosphere up to 40&thinsp;km altitude. The instrument uses a two-dimensional detector array and an imaging optics with a large aperture diameter of 36&thinsp;mm and an opening angle of 4.07°&thinsp; × &thinsp;4.07° for infrared limb observations. To overfill the field of view (FOV) of the instrument, a large-area blackbody radiation sources (125&thinsp;mm&thinsp; × &thinsp;125&thinsp;mm) is required for in-flight calibration.In order to meet the requirements regarding the scientific goals of the GLORIA missions, the radiance temperature of the blackbody calibration source has to be determined to better than 100&thinsp;mK and the spatial temperature uniformity shall be better than 150&thinsp;mK. As electrical resources on board a stratospheric balloon are very limited, the latent heat of the phase change of a eutectic material is utilized for temperature stabilization of the calibration source, such that the blackbody has a constant temperature of about −32&thinsp;°C corresponding to a typical temperature observed in the stratosphere.The Institute for Atmospheric and Environmental Research at the University of Wuppertal designed and manufactured a prototype of the large-area blackbody for in-flight calibration of an infrared interferometer deployed on board a long-duration balloon for stratospheric research. This newly developed calibration source was tested under lab conditions as well as in a climatic and environmental test chamber in order to verify its performance especially under flight conditions. At the PTB (Physikalisch-Technische Bundesanstalt), the German national metrology institute, the spatial radiance distribution of the blackbody was determined and traceability to the International Temperature Scale (ITS-90) has been assured. In this paper the design and performance of the balloon-borne blackbody (BBB) is presented.</p

The Reduced Background Calibration Facility 2 for Infrared Detectors, Cameras and Sources

The Physikalisch-Technische Bundesanstalt (PTB) designed a new calibration facility, the Reduced Background Calibration Facility 2 (RBCF2) and brought it recently into operation. It provides traceable calibrations of air born and space based infrared remote sensing experiments in terms of radiance temperature and spectral radiance. Traceable measurements from space require the use of calibrated stable detector systems and/or source-based calibration standards on board of the instrumentation. In any case they should be calibrated under space like conditions to ensure traceability with the smallest possible uncertainty. The RBCF2 enables therefore the calibration of radiators and detectors and cameras under cryogenic and/or vacuum conditions. The integration of the instrument under test into the RBCF2 can be done under ISO 5 clean room conditions. The general concept of the RBCF2 is to connect different sources in the source chamber and detectors in the detector chamber via a liquid nitrogen cooled beam line. Source and detector chamber also incorporate cooling facilities. Translation units in both chambers enable the RBCF2 to automatically compare and calibrate different sources and detectors with stable comparison instruments at cryogenic ambient temperatures and under a common vacuum. Reference sources for comparisons are dedicated vacuum variable temperature blackbodies, for example the vacuum medium temperature blackbody (VMTBB, 150 °C to 430 °C), the vacuum low temperature blackbody (VLTBB, -173 °C to 177 °C), the large area heatpipe blackbody (LAHBB, -60 °C to 50 °C) featuring a radiating diameter of 250 mm, the liquid nitrogen blackbody (LNBB, -196 °C) and calibrated vacuum integrating sphere radiators for UV-VIS and SWIR applications. The radiation temperatures of the reference blackbodies and the radiance of the integrating sphere radiators are traceable to the ITS-90 via the primary standards of PTB. Using the calibrated vacuum infrared standard radiation thermometer (VIRST) direct calibrations of sources in terms of radiance temperature in the wavelength range from 8 µm to 14 µm can be performed. For spectrally resolved measurements the radiation of the reference sources and the sources under test is imaged on a vacuum Fourier-Transform Spectrometer (FTS). The FTS covers the wavelength range from 0.4 µm to 1000 µm by employing detectors ranging from photomultipliers to liquid helium cooled bolometers. The different reference blackbodies enable measurements with respect to at least two reference temperatures, simultaneously. Hereby disturbances in the IR by background radiation resulting from inside the FTS can be effectively compensated. Sources can be also spatially mapped and characterized for the lateral distribution of their spectral radiance. The flexible design of the facility also allows large aperture camera characterizations and modifications for customer needs and the measurement of directional spectral emissivities over a wide temperature and wavelength range. Recent calibrations of the large aperture on-board blackbodies of the airborne GLORIA limbsounder, the on-board calibrations assembly (OBCA) of the EnMAP satellite and of the prototype on-board blackbody for FORUM mission are shown to illustrate the capabilities

The In-Flight Calibration System for the Airborne Imager GLORIA

The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an airborne imaging Fourier transform spectrometer developed for deployment on board different research aircraft such as the German research aircraft HALO or the high-flying Russian research plane M55-Geophysica. GLORIA uses a two-dimensional detector array for infrared limb observations (7–13 µm) providing detailed 2D/3D pictures of the Upper Troposphere/Lower Stratosphere (UTLS) region, which plays a crucial role in the climate system. The calibration of infrared sounding instruments is always a great challenge especially for air- and space-borne experiments when in-flight calibration becomes necessary. Due to the variable environmental conditions inside the belly-pod of HALO or inside the instrument bay of the M55-Geophysica, it is not sufficient to calibrate the instrument on the ground only. Since the instrument is exposed to the hostile environment of the UTLS (T ~ -50 °C, p \u3c 200 hPa), the in-flight calibration sources have to be carefully designed to cope with those adverse circumstances. Additional restrictions like weight limitations and power restraints are implied. GLORIA’s in-flight calibration system consists of two identical large-area (126mm x 126mm) high-precision blackbodies (GBB-C and GBB-H), which are independently controlled at two different temperatures. Thermo-Electric Coolers (TECs) are used to control the temperature of the calibration sources offering the advantage of avoiding cryogens and mechanical coolers. The achieved emissivity of the optical surface is 0.999(6) with a thermal homogeneity of about 0.1 K. The system has been comprehensively characterized for its spatially and spectrally resolved radiation properties in terms of radiation temperature traceable to the International Temperature Scale (ITS-90) at the Physikalisch-Technische Bundesanstalt (PTB), the national metrology institute of Germany. GLORIA’s in-flight calibration system was already successfully deployed during the ESSenCe campaign in 2011 and the TACTS/ESMVal campaign in 2012