21cmSense v2: A modular, open-source 21 cm sensitivity calculator

The 21cm line of neutral hydrogen is a powerful probe of the high-redshift universe (Cosmic Dawn and the Epoch of Reionization), with an unprecedented potential to inform us about key processes of early galaxy formation, the first stars and even cosmology and structure formation (Liu & Shaw, 2020), via intensity mapping.It is the subject of a number of current and upcoming lowfrequency radio experiments, including the MWA (Tingay et al., 2013), LOFAR (van Haarlem et al., 2013), HERA (DeBoer et al., 2017) and the SKA (Pritchard et al., 2015), which complement the detailed information concerning the brightest sources in these early epochs from powerful optical and near-infrared telescopes such as the JWST (Castellano et al., 2022).21cmSense is a Python package that provides a modular framework for calculating the sensitivity of these experiments, in order to enhance the process of their design.This paper presents version v2.0.0 of 21cmSense, which has been rewritten from the ground up to be more modular and extensible, and to provide a more user-friendly interface -as well as converting the well-used legacy package, presented in (Pober et al., 2013(Pober et al., , 2014) ) from Python 2 to 3. 21cmSense can compute sensitivity estimates for both map-making (Barry et al., 2019) and delay-spectrum (Parsons et al., 2012) approaches to power-spectrum estimation.The full sensitivity calculation is rather involved and computationally expensive in its most general form, however 21cmSense uses a few key assumptions