Calibration Access and Data Handbook

Procedure

A probability is calculated for a given wavelength, dispersion angle and order, according to

$$p = \Delta\beta\times \frac{d}{m\lambda}\times \sin\beta_{\rm m} \ ,$$

where $\Delta\beta$ is the width of the spectral channels in dispersion angles, $d$ is the groove spacing of the gratings, $m$ is the spectral order, $\lambda$ is the wavelength, and $\beta_{\rm m}$ is the dispersion angle for unscattered light.

The function returns a flat distribution of $1/p$ channels, with constant probability per channel of $p$.