Mr. Anton K. Kaifel Profile

Anton K. Kaifel

at ZSW

SPIE Involvement:

Author

Publications (3)

SPIE Journal Paper | 1 April 2005

Fast measurements of solar spectral UV irradiance—first performance results of two novel spectroradiometers

Uwe Feister, Anton Kaifel, Rolf-Dieter Grewe, Jasmine Kaptur, Oliver Reutter, Michael Wohlfart, Klaus Gericke

OE, Vol. 44, Issue 04, 041007, (April 2005) https://doi.org/10.1117/12.10.1117/1.1886816

KEYWORDS: Ultraviolet radiation, Clouds, Atmospheric modeling, Neural networks, Diffusers, Lamps, Stars, Optical filters, Data modeling, Instrument modeling

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Short spectral scan times of preferably less than 1 min in the UV region are an important prerequisite for modern spectroradiometers to reflect short-term solar irradiance radiation variations that can occur as a result of fast changes in cloud cover and/or cloud optical depth. Two different types of fast measuring spectroradiometers for solar UV irradiance are compared in a first field campaign: (1) the UV spectroradiometer on filter model basis (UV-SPRAFIMO) and (2) the modified version of the spectroradiometer SPECTRO 320D by Instrument Systems. The UV-SPRAFIMO instrument combines a filter radiometer with five narrowband (FWHM2.0 to 2.7 nm) filters centered at fixed wavelengths in the UV-B and UV-A regions with an advanced neural network-based model. Up to 5 measurements/s can be taken concurrently in the five wavelength channels. After averaging the measurements over preselectable time intervals, the measured irradiances are converted by the neural network model into a full spectrum from 280 to 450 nm at arbitrary wavelength steps (0.05 nm). The SPECTRO 320D spectroradiometer consists of a grating double monochromator with a cooled photomultiplier tube (PMT) receiver. The instrument version run by Deutscher Wetterdienst (DWD) is thermostatted and equipped with a Schreder type cosine diffuser as the entrance optics. A spectral scan from 290 to 450 nm with a selected 0.2-nm wavelength step takes less than 30 s. The two spectroradiometers are used in a field campaign at Izana (Tenerife Island) at a height of 2440 m above sea level (ASL) to compare measured spectral and integral values of solar irradiance. Results of that comparison and the instruments' characteristics are discussed. This first field comparison shows that due to the fast measurements regime, cloud effects on the measured spectra can be appreciably reduced. The campaign shows an acceptable agreement between the spectra measured by both instruments. It also reveals some issues for further improvements of the instrument design.

Proceedings Article | 4 November 2003 Paper

UV spectral radiometer on filter-model basis (UV-SPRAFIMO)

Anton Kaifel, Jasmine Kaptur, Oliver Reutter, Michael Wohlfart, Harry Schwander, Peter Koepke, K. Dehne, Uwe Feister, Rolf-Dieter Grewe, Michael Koehl, Franz Brucker

Proceedings Volume 5156, (2003) https://doi.org/10.1117/12.509235

KEYWORDS: Ultraviolet radiation, Radiometry, Neural networks, Clouds, Sensors, Atmospheric modeling, Data modeling, Human-machine interfaces, Ozone, Spectral resolution

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Proceedings Article | 4 November 2003 Paper

First performance results of two novel spectroradiometers developed for fast scanning of solar spectra UV irradiance

Uwe Feister, Anton Kaifel, Rolf-Dieter Grewe, Jasmine Kaptur, Oliver Reutter, Michael Wohlfart, Klaus Gericke

Proceedings Volume 5156, (2003) https://doi.org/10.1117/12.508284

KEYWORDS: Ultraviolet radiation, Clouds, Lamps, Optical filters, Stars, Calibration, Atmospheric modeling, Diffusers, Environmental sensing, Instrument modeling

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Two recently developed different types of fast spectroradiometers measuring solar UV irradiance have been compared in a field campaign: i) the UV spectroradiometer on filter model basis (UV-SPRAFIMO) and ii) the modified version of the spectroradiometer SPECTRO 320D by Instrument Systems. The all-weather UV-SPRAFIMO instrument combines a UV filter radiometer with 5 narrow-band (FBHM ≈ 2.0 to 2.5 nm) filters centered within ± 0.01 nm at 303.5, 309.0, 314.5, 327.0 and 387.0 nm, and an advanced neural network-based model. It allows up to 5 measurements per second to be taken that are averaged within time intervals between 5 and 30 s. The neural networks model that is embedded in the PC-based processing software converts the 5 measured irradiances into a full spectrum from 280 to 450 nm at small wavelength steps (≥ 0.05 nm). These spectra can be convoluted with user-defined slit function and integrated to broad-band and action-spectra-weighted irradiance values. Users can access the data stored in the internal data logger by a serial RS232 interface or by a modem and display them on a PC-based Graphical User Interface. The spectroradiometer SPECTRO320D consists of a grating double monochromator with a cooled (-20°C) PMT receiver. The modified instrument version run by DWD uses a Schreder type cosine diffuser that directs the solar global irradiance via quartz fiber optics onto the spectroradiometer's entrance slit. The spectroradiometer used at the campaign was installed in a thermostatted (22 ± 0.02)°C aluminum box. The modified instrument version performs a spectral scan over the whole UV region in two subsequent parts, with a lower speed in the UV-B than in the UV-A to account for the exponential changes of solar irradiance with increasing wavelengths in the UV-B and for the almost linear change in the UV-A region. In the configuration applied in the comparison, i.e. wavelength steps of 0.2 nm within the scan range from 290 nm to 450 nm, the resulting scan time of the SPECTRO 320D was 23 s. The two spectroradiometers, which both have been absolutely calibrated in the DWD lab using FEL 1000 W halogen lamps traceable to the German Physikalisch-Technische Bundesanstalt (PTB), were used in a field campaign at Izana (Tenerife Island) at a height of 2409 m to compare measured spectral and integral values of solar irradiance. Results of that comparison and the instruments’ characteristics revealed under those special field conditions will be discussed.

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