
Israeli-German partnership (from left to right): Otmar D. Wiestler, Helmholtz Association, Eli Waxman, Weizmann Institute, Avi Blasberger, ISA, Daniel Zajfman, Weizmann Institute, Helmut Dosch and Christian Stegmann, DESY. (Source: Weizmann Inst., I. Belson)
A new space telescope will open up an unprecedented view of the universe in ultraviolet light: The Ultrasat satellite will provide fundamental new insights into high-energy phenomena such as supernova explosions, colliding neutron stars and active black holes, all of which can also generate gravitational waves and act as cosmic particle accelerators. In October, the president of the Helmholtz Association, Otmar Wiestler, and the director of the Helmholtz center DESY, Helmut Dosch, agreed with the Weizmann Institute of Science on a cooperation for German participation in the Israeli-led project. DESY will build the 100-megapixel UV camera for the space telescope. For the project, DESY is working with the German Aerospace Center DLR, which also is a member of the Helmholtz Association.
Ultrasat will study the sky in the ultraviolet from 220 to 280 nanometers and have a particularly large field of view of 225 square degrees – about twelve hundred times as large as the full moon appears in our sky. “This unique configuration will help us answer some of the big questions in astrophysics,” said Eli Waxman, principal investigator of Ultrasat at the Weizmann Institute of Science.
Ultrasat is particularly sensitive to high-energy phenomena. “Everything that gets extremely hot shines brightly in the UV light,” reports DESY researcher Rolf Bühler, project manager for the UV camera. This includes active black holes, which absorb matter from their environment and also accelerate particles, and colliding neutron stars. The observation of neutron star crashes can not only provide information about element synthesis in the cosmos, but is also of great importance for gravitational wave research. “If gravitational waves are registered by merging neutron stars, their position can so far only be coarsely resolved on the basis of the gravitational wave data,” explains Bühler. “Ultrasat can orient itself to the target region within a maximum of thirty minutes and, thanks to its large field of view, can then determine the exact position almost immediately.”

Ultrasat observes energetic cosmic sources with a 1.2 m UV telescope and a 100 MP camera (Source: DESY)
The satellite thus has a decisive function for the young field of multimessenger astronomy, which studies the universe via various messengers such as cosmic particles, gravitational waves and electromagnetic radiation and forms a new area of research at DESY. With its large field of view, the satellite will have a particularly large section of the sky in view and will thus also be able to detect unknown objects that suddenly flare up in the UV range.
With a total weight of only 160 kilograms and a volume of less than one cubic meter, the Ultraviolet Transient Astronomy Satellite is a small scientific satellite. The Weizmann Institute of Science and the Israeli Space Agency ISA share funding and management. The launch is scheduled for 2023. Ultrasat will then collect data for three years. It will be put in a high orbit about 35,000 kilometers above Earth’s surface. This guarantees that disturbances from the ultraviolet background radiation, which Earth’s atmosphere reflects from the sun, are negligible and allows large areas of the sky to be surveyed. UV radiation can only be observed from orbit because it is largely absorbed and reflected by the atmosphere.
The UV camera, which DESY is developing and building, will be the heart of the space telescope. It will have a UV-sensitive sensor area of nine by nine centimeters and a resolution of one hundred megapixels. With these parameters, the developers are breaking new ground: A UV space camera with such a resolution and sensitivity has never been built before. DESY experts in astroparticle physics work together with specialists in synchrotron radiation detector development. With this project, DESY is contributing about five million euros to the satellite, which will cost about seventy million euros in total. (Source: DESY)
Link: ULTRASAT – Ultraviolet Transient Astronomy Satellite, Weizmann Institute of Science, Rehovot, Israel • ULTRASAT – An Ultraviolet Transient Astronomy Satellite, Israel Space Agency, Tel Aviv, Israel
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