F. Olschewski

Cryogenic infrared spectrometers and telescopes for the atmosphere: new frontiers

The new airborne CRyogenic Infrared Spectrometers and Telescope for the Atmosphere experiment (CRISTA-New Frontiers) succeeds the CRISTA satellite instrument operated twice during NASA space shuttle flights in November 1994 (STS 66) and August 1997 (STS 85). The first mission of the instrument will take place aboard the high altitude research aircraft M55-Geophysica in a campaign in the tropics in 2005/06. CRISTA-NF is a limb-scanning instrument measuring thermal emissions of various atmospheric trace gases (e.g. water vapor, ozone, chlorofluorocarbons), clouds and aerosols in the mid-infrared spectral region. The incoming radiation entering the optics through a Herschel telescope is analyzed by two Ebert-Fastie grating spectrometers with moderate spectral resolution and finally registered by cryogenic semiconductor-detectors. The optical system is integrated into a compact cryostat which reaches temperatures down to 10K by cooling with supercritical helium. This allows fast measurements and provides good signal-to-noise ratio. A narrow vertical field of view (200m) results in high vertical resolution which is neccessary for the analysis of small scale dynamic processes especially in the upper troposphere and lower stratosphere. This paper gives a scientific motivation, some remarks on the measurement technique and an overview of instrument design and technology.

In-flight blackbody calibration sources for the GLORIA interferometer

The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) deployed on board different research aircraft shall provide a detailed picture of the UTLS region. GLORIA uses a two-dimensional detector array for infrared limb-observations. The GLORIA in-flight calibration system consists of two identical large-area high-precision blackbodies, which are independently controlled at two different temperatures. Thermo-Electric Coolers are used to control the temperature of the blackbodies. 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 national metrology institute of Germany (PTB).

A highly miniaturized satellite payload based on a spatial heterodyne spectrometer for atmospheric temperature measurements in the mesosphere and lower thermosphere

A highly miniaturized limb sounder for the observation of the O2 A-Band to derive temperatures in the mesosphere and lower thermosphere is presented. The instrument consists of a monolithic spatial heterodyne spectrometer (SHS), which is able to resolve the rotational structure of the R-branch of that band. The relative intensities of the emission lines follow a Boltzmann distribution and the ratio of the lines can be used to derive the kinetic temperature. The SHS operates at a Littrow wavelength of 761.8 nm and heterodynes a wavelength regime between 761.9 nm and 765.3 nm with a resolving power of 5 about 8,000 considering apodization effects. The size of the SHS is 38x38x27 mm and its acceptance angle is ±5o. It has an etendue of 0.014 cm sr. Complemented by a front optics with a solid angle of 0.65 and a detector optics, the entire optical system fits into a volume of about 1.5 liters. This allows to fly this instrument on a 3 or 6 unit CubeSat. The vertical field of 1 Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2017-437 Manuscript under review for journal Atmos. Meas. Tech. Discussion started: 9 January 2018 c

A novel CubeSat payload for airglow measurements in the mesosphere and lower thermosphere

The Institute for Atmospheric and Environmental Research at the University of Wuppertal and the Institute of Energy and Climate Research Stratosphere (IEK-7) at the Research Center Juelich developed a novel CubeSat payload for atmospheric research. The payload consists of a small spectrometer for the observation of airglow at 762 nm. The line intensities of the oxygen A-band are used to derive temperatures in the mesosphere and lower thermosphere (MLT) region. The temperature data will be used to analyze dynamical wave structures in the atmosphere which have become increasingly important for the modeling of the climate system. Integrated in a 6U CubeSat, the instrument needs a highly accurate attitude determination and control system (ADCS) for limb sounding of the atmosphere. The agility of a CubeSat shall be used to sweep the line-of-sight through specific regions of interest to derive a three-dimensional image of an atmospheric volume using tomographic reconstruction techniques. The spectrometer technology chosen to measure the ro-vibrational structure of the O2 atmospheric band at 762 nm is a Spatial Heterodyne Interferometer (SHI) originally proposed by Pierre Connes in 1958. The throughput of an SHI is orders of magnitude larger than of a conventional grating spectrometer of the same size. It can be designed to deliver extraordinary spectral resolution to resolve individual emission lines. The utilization of a two-dimensional imaging detector allows for recording interferograms at adjacent locations simultaneously. Since an SHI has no moving parts, it can be built as a monolithic block which makes it very attractive for remote sensing, especially from space.

A large-area blackbody for inflight 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 inflight 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 5 stratosphere up to 40 km altitude. The instrument uses a two-dimensional detector array and an imaging optics with a large aperture diameter of 36 mm and an opening angle of 4.07◦ × 4.07◦ for infrared limb observations. To overfill the field-of-view (FOV) of the instrument, a large-area blackbody radiation sources (125mm× 125mm) is required for inflight 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 100mK and the spatial temperature uniformity shall be better 10 than 150mK. Since 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 ◦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 inflight calibration of an infrared interferometer deployed on board a long-duration balloon 15 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 PTB (PhysikalischTechnische 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. 20

Characterization of Large Area Calibration Blackbodies for the Imaging FTS GLORIA

GLORIA is an imaging infrared FTS measuring atmospheric limb emission spectra from aircraft. For radiometric calibration it uses two on-board blackbodies. Accuracy and homogeneity of these blackbodies are characterized and traced to ITS-90.

An in-flight blackbody calibration source for the GLORIA interferometer onboard an airborne research platform

The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) deployed on board different research aircraft provides detailed pictures of the Upper Troposphere/Lower Stratosphere (UTLS) region. GLORIA uses a two-dimensional detector array for infrared limb observations. GLORIAs in-flight calibration sources are two identical large-area high-precision blackbodies, which are independently controlled at two different temperatures. Thermo-Electric Coolers (TECs) are used to control the temperature of the calibration sources. The calibration sources have been comprehensively characterized for their 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.