Microwave telescopes require an ever-increasing control of experimental
systematics in their quest to measure the Cosmic Microwave Background (CMB) to
exquisite levels of precision. One important systematic for ground and
balloon-borne experiments is ground pickup, where beam sidelobes detect the
thermal emission of the much warmer ground while the main beam is scanning the
sky. This generates scan-synchronous noise in experiment timestreams, which is
difficult to filter out without also deleting some of the signal from the sky.
Therefore, efficient modelling of pickup can help guide the design of
experiments and of analysis pipelines. In this work, we present an extension to
the beamconv algorithm that enables us to generate time-ordered data (TOD) from
beam-convolved sky and ground maps simultaneously. We simulate ground pickup
for both a ground-based experiment and a telescope attached to a stratospheric
balloon. Ground templates for the balloon experiment are obtained by
re-projecting satellite maps of the Earth's microwave emission.Comment: 10 pages, 6 figures, paper 12190-165 for the "SPIE AT+I 2022 mm,
sub-mmm, and Far-Infrared Detectors and Instrumentation for Astronomy XI"
conferenc