eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the core instrument on the Russian/German Spektrum-Roentgen-Gamma (SRG) mission which is now officially scheduled for launch on September 2017, eROSITA will perform a deep survey of the entire X-ray sky. Within the first 4 years of the mission the sky will be scanned 8 times. In the soft band (0.5-2 keV), it will be about 30 times more sensitive than ROSAT, while in the hard band (2-8 keV) it will provide the first ever true imaging survey of the sky. eROSITA is currently (June 2016) in its final integration and test phase. All seven FM Mirror Assemblies and Camera Assemblies (+ 1 spare) have been tested and calibrated. All subsystems and components are well within their expected performances.
eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the core instrument on the Russian/German Spektrum-Roentgen-Gamma (SRG) mission which is now officially scheduled for launch on March 26, 2016. eROSITA will perform a deep survey of the entire X-ray sky. In the soft band (0.5-2 keV), it will be about 30 times more sensitive than ROSAT, while in the hard band (2-8 keV) it will provide the first ever true imaging survey of the sky. The design driving science is the detection of large samples of galaxy clusters to redshifts z < 1 in order to study the large scale structure in the universe and test cosmological models including Dark Energy. In addition, eROSITA is expected to yield a sample of a few million AGN, 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. eROSITA is currently (June 2014) in its flight model and calibration phase. All seven flight mirror modules (+ 1 spare) have been delivered and measured in X-rays. The first camera including the complete electronics has been extensively tested (vacuum + X-rays). A pre-test of the final end-toend test has been performed already. So far, all subsystems and components are well within their expected performances.
The eROSITA space telescope is currently developed for the determination of cosmological parameters and the equation of state of dark energy via evolution of clusters of galaxies. Furthermore, the instrument development was strongly motivated by the intention of a first imaging X-ray all-sky survey enabling measurements above 2 keV. eROSITA is a scientific payload on the Russian research satellite SRG. Its destination after launch is the Lagrangian point L2. The observational program of the observatory divides into an all-sky survey and pointed observations and takes in total about 7.5 years. The instrument comprises an array of 7 identical and parallel aligned telescopes. Each of the seven focal plane cameras is equipped with a PNCCD detector, an enhanced type of the XMM-Newton focal plane detector. This instrumentation permits spectroscopy and imaging of X-rays in the energy band from 0.3 keV to 10 keV with a field of view of 1.0 degree. The camera development is done at the Max-Planck-Institute for extraterrestrial physics. Key component of each camera is the PNCCD chip. This silicon sensor is a back-illuminated, fully depleted and column-parallel type of charge coupled device. The image area of the 450 micron thick frame-transfer CCD comprises an array of 384 x 384 pixels, each with a size of 75 micron x 75 micron. Readout of the signal charge that is generated by an incident X-ray photon in the CCD is accomplished by an ASIC, the so-called eROSITA CAMEX. It provides 128 parallel analog signal processing channels but multiplexes the signals finally to one output which feeds the detector signals to a fast 14-bit ADC. The read noise of this system is equivalent to a noise charge of about 2.5 electrons rms. We achieve an energy resolution close to the theoretical limit given by Fano noise (except for very low energies). For example, the FWHM at an energy of 5.9 keV is approximately 140 eV. The complete camera assembly comprises the camera head with the detector as key component, the electronics for detector operation as well as data acquisition and the filter wheel unit. In addition to the on-chip light blocking filter directly deposited on the photon entrance window of the PNCCD, an external filter can be moved in front of the sensor, which serves also for contamination protection. Furthermore, an on-board calibration source emitting several fluorescence lines is accommodated on the filter wheel mechanism for the purpose of in-orbit calibration. Since the spectroscopic silicon sensors need cooling down to -95°C to mitigate best radiation damage effects, an elaborate cooling system is necessary. It consists of two different types of heat pipes linking the seven detectors to two radiators. Based on the tests with an engineering model, a flight design was developed for the camera and a qualification model has been built. The tests and the performance of this camera is presented in the following. In conclusion an outlook on the flight cameras is given.