ULTRASAT is a scientific mini-satellite carrying a telescope with an unprecedentedly large field of view (250 squared degrees), that will conduct the first wide-field survey of transient and variable ultraviolet (UV, 220-280nm) sources. ULTRASAT will revolutionize our understanding of the hot transient universe: the extra-Galactic volume, that will be accessible to ULTRASAT for the discovery of transient sources, is 300 times larger than that of the most sensitive UV satellite to date, GALEX, and comparable to that of the largest ground-based optical transient survey planned to begin operation in 2022, LSST. 

ULTRASAT will have a broad science impact across the fields of gravitational wave sources, supernovae, variable and flare stars, active galactic nuclei, tidal disruption events, compact objects, and galaxies. It will open a new wave band (UV) and cadence access (minutes to months), with a vast space for serendipitous discovery. All ULTRASAT data will be transmitted to the ground in real time, and transient alerts will be distributed to the community in <20 min, driving a vigorous ground-based follow-up of static, variable and transient ULTRASAT sources. 

One of the key science goals of ULTRASAT is the discovery of electro-magnetic emission following the detection of gravitational waves (GW) from the mergers of binaries involving neutron stars. Such detections will be the key to using these events for addressing fundamental physics questions, such as the origin of the heaviest elements and the expansion rate of the universe. ULTRASAT will be able to slew in minutes to >50% of the sky, and its wide field-of-view amply covers the angular error regions expected to be provided by GW detectors in the 2020s. It will provide continuous UV light curves as well as early alerts that will enable ground-based follow-up spectroscopy and monitoring of optical and infrared emission predicted to arise later. 

The ULTRASAT time line calls for a mission kickoff during Q3 of 2019 and a launch target date in early 2023. This plan is designed in order to reach space during the early phase of the planned full sensitivity operation of the GW detector network. 

ULTRASAT is planned for a 3-year operation at a GEO orbit. Its small mass and volume, 160 kg and <1m3, allows a launch to GEO as a secondary payload. 

The ULTRASAT spacecraft will be constructed by the Israeli Aerospace Industry (IAI), and the telescope will be constructed by Elbit/Elop. ULTRASAT is jointly funded and managed by the Israel Space Agency (ISA) and the Weizmann Institute of Science (WIS), under the scientific leadership of the WIS. Mission operations will be provided by IAI, and science operations (including data pipeline, transient alerts, and data products) will be provided by the WIS.

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