How to Pamper your Optics: Environment Control for Argus Optical Array

Wide field surveys using small-aperture, mass-produced telescopes have the potential to lower the cost barrier to astrophysics by orders of magnitude. The Argus Array series of instruments will open new pathways into the study of optical transients via high-cadence, all-sky imaging. The series prototype, the Argus Technology Demonstrator, consists of nine 8-inch telescopes enclosed in a thermally-controlled dome and observing representative patches of the entire sky for 9 minutes a night. Next, Argus Pathfinder will observe a continuous declination stripe with about 45 telescopes. The project is planned to culminate with the Argus Optical Array observing the entire Northern sky simultaneously at 1-minute cadence with over 900 telescopes. As the number of telescopes increases, so do the maintenance requirements. For an open-air array, this could result in operations costs far in excess of those of an equivalent monolithic telescope and lead to inconsistent sky coverage while parts of the array are offline. To limit wear and the need for cleaning, re-alignment and focusing, we seal our telescopes in a filtered and air-conditioned enclosure. This is maintained within a ΔT small enough to prevent measurable changes in telescope focus, and the rate and distribution of cool-air flow is controlled with PWM fans. The enclosure shell is insulated as much as space allows and the temperature set seasonally (10 C in winter, 20 C in summer) to minimize convection from the windows in cold weather. Here we will present our design and initial performance of the Pathfinder environmental control system.