ULTRASAT is a scientific mini-satellite carrying a telescope with an unprecedentedly large field of view (250 squared degrees) observing in the ultraviolet (UV, 220-280nm), that is proposed by an Israeli/US collaboration to be constructed and launched to a (near) geostationary orbit by 2021/2022. ULTRASAT will revolutionizing our understanding of the transient UV universe, providing a unique insight into a broad variety of transient phenomena: neutron stars mergers generating blasts of gravitational waves and ejecting radioactive matter, explosive deaths of massive stars, disruptions of stars by super-massive black holes and many more.

ULTRASAT’s ability to revolutionize the field of transient astronomy is enabled by the combination of a wide field of view and a cutting-edge technology of UV detectors. ULTRASAT will explore a new region of parameter space in both wavelength and cadence (minutes to months), with a discovery rate >300 times larger than ever before. It will provide continuous NUV light curves to depths comparable to contemporary ground and space-based time-domain surveys at longer wavelengths (e.g. LSST, which is expected to begin operation after 2022).

ULTRASAT’s key science goals are:

  1. Collect early UV light curves of hundreds of core-collapse supernovae, to measure the radii and surface composition of their massive progenitors, and to determine explosion parameters. Connecting the pre-explosion stars with their diverse explosive output will chart how the population of massive stars impact their environment through mass loss and explosion, and will specify initial conditions for explosion models.
  2. Search for electro-magnetic emission from gravitational wave (GW) sources. Ejecta from mergers involving neutron stars are predicted to radiate UV light detectable by ULTRASAT in their earliest phases. ULTRASAT will be able to slew in minutes to 50% of the sky, and its wide field-of-view amply covers the error ellipses expected from GW detectors in the 2020s.
  3. Provide continuous NUV light curves of hundreds of supernovae of all types, hundreds of tidal disruptions of stars by super-massive black holes, thousands of active galactic nuclei, and >105 flaring and variable stars. Rapid transient alerts will be provided to the global astronomical community, and all data products including light curves will be made available and updated daily.

ULTRASAT will provide cutting edge science with a satellite mission which is significantly smaller (~1m3), lighter (~100kg) and cheaper (~$100M, including launch) than most space missions. The success of ULTRASAT will lead the way to future similar missions.

NASA, ISA, Weizmann Institute of Science, IAI,JPL, SSL, Ebit Systems