Design of the ULTRASAT UV camera

Abstract

The Ultraviolet Transient Astronomical Satellite (ULTRASAT) is a scientific UV space telescope that will operate in geostationary orbit. The mission, targeted to launch in 2024, is led by the Weizmann Institute of Science (WIS) in Israel and the Israel Space Agency (ISA). Deutsches Elektronen Synchrotron (DESY) in Germany is tasked with the development of the UV-sensitive camera at the heart of the telescope. The camera's total sensitive area of ≈ 90 mm × 90 mm is built up by four back-side illuminated CMOS sensors, which image a field of view of ≈ 200 deg 2 . Each sensor has 22.4 megapixels. The Schmidt design of the telescope locates the detector inside the optical path, limiting the overall size of the assembly. As a result, the readout electronics is located in a remote unit outside the telescope. The short focal length of the telescope requires an accurate positioning of the sensors within ±50 µm along the optical axis, with a flatness of ±10 µm. While the telescope will be at around 295 K during operations, the sensors are required to be cooled to 200 K for dark current reduction. At the same time, the ability to heat the sensors to 343 K is required for decontamination. In this paper, we present the preliminary design of the UV sensitive ULTRASAT camera.

Science with the Ultraviolet Explorer (UVEX)

“…ULTRASAT will observe in the NUV (2200-2800 Å) with a wide FOV of 200 deg 2 . The camera is equipped with a mosaic of four backsideilluminated Complementary metal-oxide-semiconductor (CMOS) detectors and will reach a sensitivity of ∼ 22.3 mag (AB; 5σ) in 3 × 300 s exposures (Asif et al 2021). ULTRASAT will be placed in GEO and data will be transferred to the ground in real time.…”