The eROSITA X-ray telescope on SRG

eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the primary instrument on the Spectrum-Roentgen-Gamma (SRG) mission, which was successfully launched on July 13, 2019, from the Baikonour cosmodrome. After the commissioning of the instrument and a subsequent calibration and performance verification phase, eROSITA started a survey of the entire sky on December 13, 2019. By the end of 2023, eight complete scans of the celestial sphere will have been performed, each lasting six months. At the end of this program, the eROSITA all-sky survey in the soft X-ray band (0.2-2.3 keV) will be about 25 times more sensitive than the ROSAT All-Sky Survey, while in the hard band (2.3-8 keV) it will provide the first ever true imaging survey of the sky. The eROSITA design driving science is the detection of large samples of galaxy clusters up to redshifts z > 1 in order to study the large-scale structure of the universe and test cosmological models including Dark Energy. In addition, eROSITA is expected to yield a sample of a few million AGNs, including obscured objects, revolutionizing our view of the evolution of supermassive black holes. The survey will also provide new insights into a wide range of astrophysical phenomena, including X-ray binaries, active stars, and diffuse emission within the Galaxy. Results from early observations, some of which are presented here, confirm that the performance of the instrument is able to fulfil its scientific promise. With this paper, we aim to give a concise description of the instrument, its performance as measured on ground, its operation in space, and also the first results from in-orbit measurements

The eROSITA camera array on the SRG satellite

The SRG satellite with the eROSITA X-ray telescope as scientific payload was successfully launched on July 13, 2019 and deployed in a 6-month halo orbit around the second Lagrange point of the Sun Earth system. The telescope comprises an array of seven mirror systems with seven focal plane cameras. The spectroscopic CCD cameras are a further development of the very successful EPIC PN camera on the XMM-Newton satellite, which is after 20 years in space still successfully operating. Key component of the camera is the detector, which matches the large field of view of 1° to permit an all-sky survey in the energy range from 0.2 keV to 8 keV with state-of-the-art energy resolution. The image area of the PNCCD comprises 384 x 384 pixels. Their size of 75 x 75 μm2 each, matches the angular resolution of the mirror system. Readout of the full frame is achieved in 9.18 ms but for thermal and onboard event pre-processing reasons, the time resolution is slowed down to 50 ms. The photon entrance window of five of the seven CCDs is equipped with an optical blocking filter, which turned out to be advantageous. The improved concept and design of the eROSITA cameras will be explained as well as their operation and performance in space

Spectroscopic performances of depmos detector/amplifier device with respect to different filtering techniques and operating conditions

DePMOS structure provides detection and amplification jointly and it is free of interconnection stray capacitance. An electrical model of the device has been provided. The most relevant parameters have been measured in order to choose an adequate readout electronics, to fully exploit the intrinsic low noise of the device. DePMOS can operate in continuous mode, i.e. without applying any clear pulse during the signal processing, and can be read out by a time continuous shaper amplifier. An unequalled noise of 2.2 electrons r.m.s. at room temperature has been measured. In this mode DePMOS can be used e.g. as the readout device for silicon drift detectors. DePMOS was developed to be the basic element of an active pixel sensor suitable to cope with the requirements of XEUS wide field imager. In a matrix arrangement, each pixel must be read out by a time variant filter. A multichannel integrated shaping amplifier, based on multi correlated double sampling, has been designed. Spectroscopic resolution obtained filtering the pixel matrix with this readout chip is in agreement with measurements in continuous mode and matches the predictions of the model presented. It has also been experimentally proved that the clear procedure doesn't introduce additional noise contribution, even in the very low noise range achieved. This qualifies DePMOS as a "reset-noise-free" device