ULTRASAT is a scientific satellite that is planned to be launched to GEO orbit in Q2 2026. It will be carrying a telescope with an unprecedentedly large field of view (204 squared degrees), that will conduct the first wide-field survey of transient and variable ultraviolet (UV, 230-290nm) 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 2024, LSST.
ULTRASAT will have a broad scientific impact across the fields of Gravitational Wave (GW) 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 <15 min, driving vigorous ground-based follow-up of static, variable and transient ULTRASAT sources.
A key science goal 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 starting 2025. 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.
ULTRASAT is planned for a 3-year operation at a GEO orbit, with fuel sufficient to enable an extension to 6 years of operation. It is planned to reach space prior to or during the early phase of the planned full sensitivity operation of the GW detector network.
The ULTRASAT spacecraft is being constructed by the Israeli Aerospace Industry (IAI), the telescope is being constructed by Elbit/Elop, and the UV camera is being constructed by DESY Zeuthen. The launch (as a secondary payload) will be provided by NASA. ULTRASAT is jointly funded and managed by the Israel Space Agency (ISA), the Weizmann Institute of Science (WIS), and DESY, 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 WIS.
ULTRASAT is groundbreaking both in terms of science and in terms of implementation. If successful, we will demonstrate that breakthrough science can be achieved by small satellites at an affordable cost, ~$100M including launch, leading the way to future similar missions. Beyond providing groundbreaking science, the high scientific profile of the mission will strengthen the world standing of the Israeli space industry as well as the international standing of Israel via the creation of collaborations with leading industries and agencies. It will also have a major educational impact drawing young talented Israeli people to science and technology.