The Navy Precision Optical Interferometer: large-aperture observations and infrastructure improvements

We have been progressing on our comprehensive program of improving high-resolution imaging at the Navy Precision Optical Interferometer (NPOI) hosted at Lowell Observatory's Anderson Mesa site, for the purpose of spatially resolved observations of faint objects at scales down to less than 1 milliarcsecond. The `PALANTIR' upgrade of NPOI has commenced with individually operating 1 meter PlaneWave PW1000 telescopes at the site, with integration of those telescopes into the array with interferometric operations expected in the near-term. These telescopes are housed in mobile domes for rapid relocation around the array, and are being augmented with adaptive optics. Another notable recent milestone has been the re-activation of full six-way on-sky operations with siderostat feeds during the summer of 2021. Additionally, our `NPOI Plus-Up' plan will implement sweeping infrastructure updates, improving and streamlining its operations. Upcoming Plus-Up work taking place over the next few years includes expansion of the operating infrastructure to the array's longest physical baselines at 432 meters, adding a near-infrared beam combiner, rehabilitation of the VISION visible combiner, modernization of the fast delay line control system, and implementation of the long delay lines in the framework of a beam train auto-aligner.