Abstract
The Spectrum-Roentgen-Gamma satellite with the extended roentgen survey with an imaging telescope array (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 still operating after more than 20 years in space. The key component of the camera is the detector, which matches the large field of view of 1 deg to permit an all-sky survey in the energy range from 0.2 to 8 keV with state-of-the-art energy resolution. The image area of the PN-junction charge coupled device comprises 384 × 384 pixels. The pixel size of 75 × 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 preprocessing 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 proved to be advantageous. The improved concept and design of the eROSITA cameras will be explained as well as their operation and performance in space.
Highlights
The extended roentgen survey with an imaging telescope array x-ray telescope has been developed to perform an all-sky survey in the energy band from 0.2 to 8 keV
The detectors for eROSITA have been developed based on the EPIC-PN detector but taking into account lessons learned during the XMM-Newton project
A higher robustness with respect to environmental conditions was achieved by passivation of the front surface and an optical light blocking filter directly deposited on the sensor
Summary
The extended roentgen survey with an imaging telescope array (eROSITA) x-ray telescope has been developed to perform an all-sky survey in the energy band from 0.2 to 8 keV It is the primary instrument of the Spectrum-Roentgen-Gamma mission,[1] which was successfully launched on July 13, 2019, from the Baikonour cosmodrome. Extending the exposure time per frame to 50 ms means a minimization of the heat dissipation of the focal plane detector to only 0.7 W This means that the readout ASIC is switched 20 times per second into standby mode during nominal detector operation. By this method, the optimum temperature of −95°C with respect to radiation damage mitigation[5] should be achieved for the array of seven detectors according to the thermal design with two radiator panels and associated heat pipe system.
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