Abstract We report systematic issues commonly observed in the Hydrogen Epoch of Reionization Array (HERA) observations that cause abrupt changes in power over time, resulting in temporal discontinuities. To identify these effects, we applied the Temporal Discontinuity Index (TDI) and Spectral Discontinuity Index (SDI) metrics, which complement existing diagnostic tools by detecting discontinuities and revealing their potential relationships to bandpass and power-related issues. Analysis of 30 datasets, each corresponding to a single observing night, shows that such systematics appear consistently in many antennas and across multiple nights. Based on these metrics, we identify three main types of discontinuity-related issues: periodic broadband discontinuities linked to Inter-Integrated Circuit (I2C) polling, broadband discontinuities associated with degraded post-amplifier modules (PAMs), and sudden power changes related to the digital back-end of the antenna system. The second type, associated with degraded PAMs, occurs less frequently within a single night compared to the periodic polling effect, though both are broadband. The third type affects the largest number of antennas and is most prevalent in the H6C data. The width of the discontinuities related to the digital back-end corresponds to the frequency range handled by a single correlator box, scaled by the number of boxes involved. Although 30 datasets were examined, this paper presents a focused analysis of four representative nights to highlight the main discontinuity issues. We also present correlations between flagging due to discontinuities and flagging caused by other failure modes to investigate how these issues are interrelated.
Hailemariam et al. (2026) studied this question.