  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 ~90mm x 90mm
is built up by four back-side illuminated CMOS sensors, which image a field of
view of ~200 deg2. 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 mu along the
optical axis, with a flatness of +-10 mu. While the telescope will be at around
295K during operations, the sensors are required to be cooled to 200K for dark
current reduction. At the same time, the ability to heat the sensors to 343K is
required for decontamination. In this paper, we present the preliminary design
of the UV sensitive ULTRASAT camera.
