Frequency or wavelength range of the laboratory testbed Sample Clauses

Frequency or wavelength range of the laboratory testbed. For reasons obvious to the reader, the spectral coverage of the testbed is best arranged where the atmospheric transmission is maximum (if the testbed is in normal laboratory conditions). This allows for minimal impact from water vapour absorption and overall air turbulence. Nevertheless, water vapour lines can be useful for overall calibration as is the case in both the original FIR and the subsequent MIR upgrade. For laboratory testbeds only, water vapour lines can provide (in the case of point-like sources) independent verification of the basic angle of incidence from the sky-simulating collimator. In order to do so, the conversion of incident angle at the telescopes needs to be converted into the collimated propagation angle through the FTS delay stage of the double-Fourier dynamic arm, as the angled propagation within this stage is what introduces the 1/cos factor that modifies the recovered wavenumber axis post-FT. Future testbeds which embark in demonstrating the entire bandwidth coverage in a range where atmospheric absorption does not normally allow it, would have to employ an entirely sealed environment (such as nitrogen flushed chamber) to allow sufficient optical transmission to detect power at all in-band wavelengths. Such arrangement is non-trivial and introduces additional issues (turbulence and vibration) which have been successfully controlled in the optical testbed at Xxxxxxx [5].