ATLAS: A High-Cadence All-Sky Survey System

TL;DR

ATLAS delivers near all‑sky, nightly monitoring down to about $m\sim19$ with a two‑unit, replicable design built around 0.5 m Wright Schmidt telescopes and a high‑throughput, autonomous data pipeline. The system optimizes survey speed per unit cost and demonstrates competitive near‑Earth asteroid detection while enabling broad time‑domain science, including supernovae, transients, and gravitational‑wave counterparts. Key achievements include thousands of NEA/PHA detections, millions of transient observations, rapid public reporting, and impactful follow‑ups like the GW170817 kilonova, underscoring the value of a scalable, low‑cost all‑sky survey. The work also outlines a clear path for southern expansion to achieve continuous 24 h coverage and enhanced NEA statistics.

Abstract

Technology has advanced to the point that it is possible to image the entire sky every night and process the data in real time. The sky is hardly static: many interesting phenomena occur, including variable stationary objects such as stars or QSOs, transient stationary objects such as supernovae or M dwarf flares, and moving objects such as asteroids and the stars themselves. Funded by NASA, we have designed and built a sky survey system for the purpose of finding dangerous near-Earth asteroids (NEAs). This system, the "Asteroid Terrestrial-impact Last Alert System" (ATLAS), has been optimized to produce the best survey capability per unit cost, and therefore is an efficient and competitive system for finding potentially hazardous asteroids (PHAs) but also for tracking variables and finding transients. While carrying out its NASA mission, ATLAS now discovers more bright ($m < 19$) supernovae candidates than any ground based survey, frequently detecting very young explosions due to its 2 day cadence. ATLAS discovered the afterglow of a gamma-ray burst independent of the high energy trigger and has released a variable star catalogue of 5$\times10^{6}$ sources. This, the first of a series of articles describing ATLAS, is devoted to the design and performance of the ATLAS system. Subsequent articles will describe in more detail the software, the survey strategy, ATLAS-derived NEA population statistics, transient detections, and the first data release of variable stars and transient lightcurves.

Figures (12)

• Figure 1: The ATLAS unit on Haleakala from inside the dome.
• Figure 2: Left: Light enters the Schmidt corrector of the DFM telescope (thin blue section on the left), passes the prime focus supported by a spider assembly, reflects off of the primary mirror on the right, returns through field correctors (three blue lenses), a filter (magenta), and a cryostat window (gray) before arriving at the detector. The overall length from shutter to back of mirror cell is 1.9 m, the focus unit adding another 0.4 m, and the diameter of the mirror cell is 0.8 m. Right: A detail of the field lens and camera assembly illustrates the close spacing of the third field lens, filter, cryostat window, and CCD. The distance from Schmidt corrector to back of cryostat is 0.26 m, from there to the first field lens is 0.33 m, and the diameter of the field corrector and camera housing is 0.25 m.
• Figure 3: Left: The quantum efficiency measured at $-50$ ∘C$^\circ$C relative to a Hamamatsu photodiode with NIST-traceable calibration for out two CCDs. Right: The calculated total throughput from multiplying the traces of our primary $c$ (blue), $o$ (orange), and $t$ (red) filters (converted to f/2), 1.2 airmasses of extinction, AR coatings, and a factor of 0.92 for the enhanced coating on the mirror.
• Figure 4: The left image shows a fisheye view of a typical partially cloudy night. Clouds are evident, but their visibility depends on the illumination (sodium light from Honolulu) and their opacity is impossible to quantify. The right image shows the zero point derived for 5,027 stars in the field, with transparency indicated by point color. The clouds are obvious, and it is also possible to quantify the effects of faint clouds and extinction.
• Figure 5: Recent ATLAS coverage of the sky over four successive nights by Mauna Loa (left) and Haleakala (right). The bottom row shows the cumulative coverage for each summit. Color codes the number of visits: blue through red is 1--4 visits. Gaps arise because of imperfect weather, duplicates because of morning clouds in the east compelled the schedule to widen Dec coverage.