The Large Array Survey Telescope (LAST)
The Large Array Survey Telescope (LAST) is a wide-field visible-light telescope array designed to explore the variable and transient sky with high cadence. A LAST node is composed of 48, 28-cm f/2.2 telescopes equipped with full-frame, backside-illuminated, cooled CMOS detectors. Each telescope provides a field of view (FoV) of 7.4 deg2, so the system FoV is 355 deg2 when the telescopes are in divergent mode. The total collecting area of a LAST node is equivalent to a 1.9 m telescope for coaligned telescopes. The telescopes are mounted on 12 separate mounts, each carrying four telescopes. This provides significant flexibility in operating the system.
The first LAST node is under construction in Neot Smadar in the Israeli Negev desert. Currently, 12 telescopes are deployed, and the rest of the 48 telescopes are expected to be built during the first half of 2023.
Grasp and cost-effectiveness
Typically large telescope construction and operation costs scale up faster than their collecting area. This slows scientific progress, makes it expensive and complicated to increase the telescope size. Ofek & Ben-Ami (2020) showed that due to the availability of high-quality, large-format detectors with pixels smaller than about 4 microns, it is only now becoming more cost-effective to construct imaging surveys that are based on array of small telescopes.
Here cost-effectiveness is defined as the volume of space a telescope can probe per unit of time per unit cost. We call the volume per unit of time a telescope can probe: the grasp.
Moreover, the cost-effectiveness of survey telescopes which are based on wide-field telescopes equipped with large format CMOS detectors with small pixels is an order of magnitude larger than current operational survey telescopes. Therefore, LAST is a testbed for testing ideas regarding the cost-effectiveness of survey telescopes and the future of ground-based astrophysics.
Performance
The Bp 5-sigma limiting magnitude of a single 28-cm telescope is about 19.6 (21.0) in a 20s exposure (20x20 s). Astrometric two-axis precision (rms) at the bright-end is about 60 (30) mas in 20 s (20x20 s), and absolute photometric calibration, relative to GAIA, provides about 10 millimag accuracy. Relative photometric precision, in a single 20-s image, measured for bright sources over 6 min is about 3 millimag.
