Design and Development of a Tuneable Portable Radiation Source for In Situ Characterisation of Dobson Spectrometers

A tuneable and portable radiation source (TuPS) has been developed for the in-field characterization of the wavelength scale (290 nm to 350 nm) and slit function of Dobson spectrometers. TuPS emits radiation with a bandwidth of 0.1 nm and an uncertainty less than 0.02 nm in the wavelength scale, while the radiant power of emitted beam exceeds 20 nW over the spectral range of interest. The past two years of operation have included two in-field calibration campaigns that have required shipping and infield installations, and during which more than 14 Dobson spectrometers were calibrated. Over this period the long-term stability of both slit function and wavelength scale were determined to be as high as 0.02 nm. TuPS was designed so that only minor modifications are necessary to extend/shift its spectral range towards visible and near-infrared spectral regions, thereby extending its application to the spectral characterisation of other spectrometers.