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We discuss absolute calibration strategies for Phase I of the Hydrogen Epochof Reionization Array (HERA), which aims to measure the cosmological 21 cmsignal from the Epoch of Reionization (EoR). HERA is a drift-scan array with a10 degree wide field of view, meaning bright, well-characterized point sourcetransits are scarce. This, combined with HERA's redundant sampling of the uvplane and the modest angular resolution of the Phase I instrument, maketraditional sky-based and self-calibration techniques difficult to implementwith high dynamic range. Nonetheless, in this work we demonstrate calibrationfor HERA using point source catalogues and electromagnetic simulations of itsprimary beam. We show that unmodeled diffuse flux and instrumental contaminantscan corrupt the gain solutions, and present a gain smoothing approach formitigating their impact on the 21 cm power spectrum. We also demonstrate ahybrid sky and redundant calibration scheme and compare it to pure sky-basedcalibration, showing only a marginal improvement to the gain solutions atintermediate delay scales. Our work suggests that the HERA Phase I system canbe well-calibrated for a foreground-avoidance power spectrum estimator byapplying direction-independent gains with a small set of degrees of freedomacross the frequency and time axes.

Absolute Calibration Strategies for the Hydrogen Epoch of Reionization Array and Their Impact on the 21 cm Power Spectrum