Abstract
Abstract. For spectroradiometers, the characterisation of their wavelength scale and spectral bandwidth underpins the quality of measured data substantially. This characterisation can be performed using metrology-grade tuneable monochromatic sources, which are currently available only in a few laboratories worldwide. Yet in numerous applications, only the in-field calibration is a feasible solution. We have designed and developed a tuneable and portable radiation source (TuPS) in the wavelength range from 300 to 350 nm for the in-field characterisation of Dobson spectrometers' wavelength scale and slit function, with standard uncertainties better than 0.02 nm in wavelength and with the bandwidth of emitted radiation smaller than 0.13 nm full width at half maximum (FWHM). The TuPS is designed such that only minor modifications of its optical system extend/shift its spectral range towards visible and near-infrared spectral regions and thus expand its application for characterisation of any spectroradiometers in the relevant spectral region of interest.
Highlights
The optical characterisation of tuneable and portable radiation source (TuPS) light engine, both in terms of the central wavelength of its output radiation and the spectral bandwidth, was performed using the CMI reference tuneable monochromatic source consisting of the CMI fibre-coupled tuneable optical parametric oscillator laser facility (OPO)
As shown on the diagram, the power of optical radiation emitted from the TuPS output slit is measured by a calibrated 10 mm × 10 mm Si-based photodiode detector in conjunction with a calibrated transimpedance amplifier (TIA)
The tuneable and portable radiation source (TuPS) was developed as an instrument to be used for determining the slit function and centre wavelength of a Dobson spectrophotometer
Summary
Dobson and Brewer spectrophotometers are the main instruments used to monitor the ozone layer, even though Dobson spectrophotometers are no longer being manufactured (Dobson, 1968; Kerr et al, 1981). Each network type is in itself consistent, total column ozone retrieved from the two instrument types differs by up to 3 %, significantly larger than the consistency of better than ±0.5 %, which can be achieved within Brewer or Dobson spectrometer instruments’ network (Vanicek, 2006; Vanícek et al, 2012). This large discrepancy currently precludes a merging of both datasets and an eventual replacement of one instrument with another type. To the best of our knowledge, there were no commercial monochromators available which could simultaneously meet the TuPS specifications for resolution, wavelength stability and portable size requirements
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