First Year Status and Performance of the POLARBEAR-2a Cosmic Microwave Background Instrument

POLARBEAR-2a (PB-2a) is the first of three telescopes comprising the Simons Array, a cosmic microwave background (CMB) polarization observatory sensitive over a wide range of wavelengths and angular scales. The Simons Array will have a broad science reach, including primordial gravitational wave background searches and neutrino physics constraints. PB-2a, which began observing from northern Chile in 2018, has enabled many of the technologies necessary for the full operation of the Simons Array. Here, we describe the first year on-sky characterization and operation of PB-2a along with recent upgrades which improve upon the sensitivity, stability, and operability of the detector array.