The scientific payload of the Ultraviolet Transient Astronomy Satellite (ULTRASAT)

TL;DR

ULTRASAT is a highly sensitive UV space telescope with a large field of view, designed to detect and study transient astronomical events and flaring sources, promising to significantly advance our understanding of the hot transient universe.

Contribution

This paper details the design, payload, and expected performance of ULTRASAT, a novel UV satellite with unprecedented grasp and capabilities for transient astronomy.

Findings

Achieves a point spread function of ~10 arcsec across the field of view.

Demonstrates effective mitigation of out-of-band flux and stray light.

Provides expected limiting magnitudes for various astronomical objects.

Abstract

The Ultraviolet Transient Astronomy Satellite (ULTRASAT) is a space-borne near UV telescope with an unprecedented large field of view (200 sq. deg.). The mission, led by the Weizmann Institute of Science and the Israel Space Agency in collaboration with DESY (Helmholtz association, Germany) and NASA (USA), is fully funded and expected to be launched to a geostationary transfer orbit in Q2/3 of 2025. With a grasp 300 times larger than GALEX, the most sensitive UV satellite to date, ULTRASAT will revolutionize our understanding of the hot transient universe, as well as of flaring galactic sources. We describe the mission payload, the optical design and the choice of materials allowing us to achieve a point spread function of ~10arcsec across the FoV, and the detector assembly. We detail the mitigation techniques implemented to suppress out-of-band flux and reduce stray light, detector properties including measured quantum efficiency of scout (prototype) detectors, and expected performance (limiting magnitude) for various objects.