The scientific payload of the Ultraviolet Transient Astronomy Satellite (ULTRASAT)
Sagi Ben-Ami, Yossi Shvartzvald, Eli Waxman, Udi Netzer, Yoram Yaniv, Viktor M. Algranatti, A. Gal‐Yam, Ofer Lapid, E. O. Ofek, J. Topaz, Iair Arcavi, Arooj Asif, Shlomi Azaria, Eran Bahalul, Merlin F. Barschke, Benjamin Bastian-Querner, D. Berge, Vlad D. Berlea, Rolf Bühler, Louise Dittmar, Anatoly Gelman, G. Giavitto, Or Guttman, Juan M. Haces Crespo, Daniel Heilbrunn, Arik Kachergincky, Nirmal Kaipachery, M. Kowalski, S. R. Kulkarni, Shashank Kumar, D. Küsters, Tuvia Liran, Yonit Miron-Salomon, Zohar Mor, A. Nir, Gadi Nitzan, Sebastian Philipp, А. Порелли, Ilan Sagiv, J. S. Schliwinski, Tuvia Sprecher, N. De Simone, Nir Stern, Nicholas C. Stone, Benjamin Trakhtenbrot, Mikhail Vasilev, Jason Watson, Francesco Zappon
Abstract
The Ultraviolet Transient Astronomy Satellite (ULTRASAT) is a space-borne near UV telescope with an unprecedented large field of view (200 deg<sup>2</sup> ). 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/Q3 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 ∼ 10 arcsec 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.