Reference data needed for forward modelling of NIRSpec MSA data, as described in de Graaff et al. 2023 (https://arxiv.org/abs/2308.09742). This dataset contains a library of traces for each NIRSpec filter/disperser combination, providing a mapping from a microshutter s_{i,j} and wavelength to the position in the detector plane, and includes the rotation angle of the slitlet with respect to the trace in the detector plane. Other files provide information on the detector, such as the pixel size and the kernels used to model the inter-pixel capacitance. These data are designed to be used together with the NIRSpec MSA forward modelling code msafit, which is available publicly on github: https://github.com/annadeg/jwst-msafit