A Payload Experts group is dedicated to (discussing the findings of the) monitoring of the health of the Gaia payload, which is routinely done by First Look (Section 2.5.2), and is formed primarily by DPAC members who are directly involved with processing the Gaia’raw’ data stream on a daily or semi-daily basis (Section 1.2.3), as well as members of the Project Office (Section 1.2.2), Gaia’s Mission Manager and Project Scientist (see https://www.cosmos.esa.int/web/gaia/esa-team), and members of ESA’s Science Operations Centre (Section 1.1.5). During Gaia’s Commissioning phase, the Payload Experts played a critical and intensive role in verifying the operational health of the payload, assisting in the adjustment of payload calibration and configuration parameters (such as the spin rate and focussing), and in the early identification of various instrument anomalies and investigation into their root causes, including a variable, and higher-than-expected, background and the periodic variation of Gaia’s basic angle. During the routine science operations phase, the Payload Experts continue to monitor the instrument status (such as optical throughput and quality) and of various, known instrument issues that (may) impact the quality of the science data. The Payload Experts propose adjustments in the payload operating parameters as well as signal the need for decontamination and refocussing campaigns. The description of the current instrument status in Section 1.3.3 gives some concrete examples of their efforts.