Full-sky beam convolution for cosmic microwave background applications
  We introduce a publicly available full-sky beam convolution code library
intended to inform the design of future cosmic microwave background (CMB)
instruments and help current experiments probe potential systematic effects.
The code can be used to assess the impact of optical systematics on all stages
of data reduction for a realistic experiment, including analyses beyond power
spectrum estimation, by generating signal timelines that may serve as input to
full analysis pipelines. The design and mathematical framework of the Python
code is discussed along with a few simple benchmarking results. We present a
simple two-lens refracting telescope design and use it together with the code
to simulate a year-long dataset for 400 detectors scanning the sky on a
satellite instrument. The simulation results identify a number of sub-leading
optical non-idealities and demonstrate significant B-mode residuals caused by
extended sidelobes that are sensitive to polarized radiation from the Galaxy.
For the proposed design and satellite scanning strategy, we show that a full
physical optics beam model generates B-mode systematics that differ
significantly from the simpler elliptical Gaussian model. The code is available
at https://github.com/adrijd/beamconv
