Introducing the Condor Array Telescope. 1. Motivation, Configuration, and Performance

Résumé : The "Condor Array Telescope" or "Condor" is a high-performance "array telescope" comprised of six apochromatic refracting telescopes of objective diameter 180 mm, each equipped with a large-format, very low-read-noise ($\approx 1.2$ e$^-$), very rapid-read-time ($< 1$ s) CMOS camera. Condor is located at a very dark astronomical site in the southwest corner of New Mexico, at the Dark Sky New Mexico observatory near Animas, roughly midway between (and more than 150 km from either) Tucson and El Paso. Condor enjoys a wide field of view ($2.29 \times 1.53$ deg$^2$ or 3.50 deg$^2$), is optimized for measuring both point sources and extended, very low-surface-brightness features, and for broad-band images can operate at a cadence of 60 s (or even less) while remaining sky-noise limited with a duty cycle near 100\%. In its normal mode of operation, Condor obtains broad-band exposures of exposure time 60 s over dwell times spanning dozens or hundreds of hours. In this way, Condor builds up deep, sensitive images while simultaneously monitoring tens or hundreds of thousands of point sources per field at a cadence of 60 s. Condor is also equipped with diffraction gratings and with a set of He II 468.6 nm, [O III] 500.7 nm, He I 587.5 nm, H$\alpha$ 656.3 nm, [N II] 658.4 nm, and [S II] 671.6 nm narrow-band filters, allowing it to address a variety of broad- and narrow-band science issues. Given its unique capabilities, Condor can access regions of "astronomical discovery space" that have never before been studied. Here we introduce Condor and describe various aspects of its performance.