The Camera Head of the Wide Field Imager (WFI), which is to fly on the X-ray telescope NewAthena, is a compact sub-system requiring the integration of three separate temperature regions. One will be the environment temperature of the instruments support structure. The other two temperature environments are governed by the requirements of the detector front-end electronics and the sensor itself. Due to the limited space available and high heat fluxes that the system needs to remove at temperatures as low as 160 K, graphene thermal straps are used. Although already in use in some space applications, space qualified graphene thermal straps are not available on the market, therefore a qualification program, specific for the environmental conditions and requirements of the WFI system, has been carried out. The thermal straps are tested for their thermal performance, structural stability and particle shedding, thermally cycled and outgassed.
The filter wheel (FW) assembly (FWA), developed by the CBK Institute, is one of the critical subsystems of the wide field imager (WFI) instrument on board the Advanced Telescope for High Energy Astrophysics—mission of the ESA Cosmic Vision 2015-25 space science program (launch scheduled around 2035). The instrument has to collect soft x-rays with very high quantum efficiency, thus WFI requires extremely thin optical blocking filter (OBF). Due to its thickness (∼150 nm) and large area (∼170 mm × 170 mm) needed to achieve a 40 ′ × 40 ′ instrument field of view, the filter is extremely vulnerable to acoustic loads generated during Ariane 6 rocket launch. On the other side, FW mechanism has to provide high overall reliability, so it is more favourable to launch the instrument in atmospheric pressure (without vacuum enclosure for filter protection). Design efforts of the FW subsystem were focused on two issues: providing maximal possible sound pressure level suppression and smallest possible differential pressure across the OBF, which should prevent filters from damaging. We describe the design of a reconfigurable acoustic-demonstrator model (DM) of WFI FWA created for purposes of acoustic testing. Also, the acoustic test campaign is described: test methodology, test criteria, and results discussion and its implication on future FWA design. In general, tests conducted with the FWA DM showed that current design of WFI is feasible and the project can be continued without introducing a vacuum enclosure, which would significantly increase system complexity and mass.
X-ray telescopes opened up a new window into the high-energy universe. However, the last generation of these telescopes encountered an unexpected problem: their optics focused not only x-rays but low-energy (so called soft) protons as well. These protons are very hard to model and can not be distinguished from x-rays. For example, 40% of XMM-Newton observations is significantly contaminated by soft proton induced background flares. In order to minimize the background from such low-energy protons the advanced telescope for high energy astrophysics (ATHENA) satellite introduced a novel concept, the so called charged particle diverter (CPD). It is an array of magnets in a Hallbach design, which deflects protons below 76 keV before they would hit the wide field imager (WFI) detector. In this work, we investigate the effect of scattering of the deflected protons with the CPD walls and the inner surfaces of the WFI detector assembly. Such scattered protons can loose energy, change direction and still hit the WFI. In order to adopt the most realistic instrument model, we imported the CAD model of both the CPD and the WFI focal plane assembly. Soft protons corresponding to ≈2.5 hours of exposure to the L1 solar wind are simulated in this work. The inhomogeneous magnetic field of the CPD is included in the simulation. We present a preliminary estimate of the WFI residual background induced by soft proton secondary scattering, in the case of the optical blocking filter present in the field of view. A first investigation of the volumes responsible for scattering the protons back into the field of view is reported.
The last generation of x-ray focusing telescopes operating outside the Earth’s radiation belt discovered that optics were able to focus not only astrophysical x-ray photons, but also low-energy heliophysical protons entering the field of view (FOV). This “soft proton” contamination affects around 40% of the observation time of XMM-Newton. The ATHENA charged particle diverter (CPD) was designed to use magnetic fields to move these soft protons away from the FOV of the detectors, separating the background-contributing ions in the focused beam from the photons of interest. These magnetically deflected protons can hit other parts of the payload and scatter back to the focal plane instruments. Evaluating the impact of this secondary scattering with accurate simulations is essential for the CPD scientific assessment. However, while Geant4 simulations of grazing soft proton scattering on x-ray mirrors have been recently validated, the scattering on the unpolished surfaces of the payload (e.g. the baffle or the diverter itself) is still to be verified with experimental results. Moreover, the roughness structure can affect the energy and angle of the scattered protons, with a scattering efficiency depending on the specific target volume. Using atomic force microscopy to take nanometer-scale surface roughness measurements from different materials and coating samples, we use Geant4 together with the CADMesh library to shoot protons at these very detailed surface roughness models to understand the effects of different material surface roughnesses, coatings, and compositions on proton energy deposition and scattering angles. We compare and validate the simulation results with laboratory experiments, and propose a framework for future proton scattering experiments.
The power of eROSITA (extended ROentgen Survey with an Imaging Telescope Array), the core instrument on the Russian–German Spectrum–Roentgen–Gamma (SRG) mission, is high sensitivity at high spectral, spatial, and temporal resolution over a large field of view. This is achieved by combining 7 coaligned X–ray telescope modules, each composed of 54 paraboloid / hyperboloid mirror shells in a Wolter–I geometry, to focus the X–rays through optical blocking filters onto PNCCDs with a total of 1 million pixels, providing a spectral resolution of 60 – 160 eV FWHM over an energy range 0.2 – 8 keV and a 1 degree field of view at a time resolution of 50 ms. In order to make full scientific use of the unique capabilities of eROSITA, all the individual components have to be calibrated. The initial ground calibration was done at the PANTER and PUMA facilities of MPE as well as at BESSY, and was supplemented by an in–orbit calibration. We report on the extensive and often challenging calibration activities performed on ground and in space.
The Wide Field Imager (WFI) is one of two focal plane instruments of the Advanced Telescope for High-Energy Astrophysics (Athena), ESA’s next large X-ray observatory, planned for launch in the early 2030’s. In the aimed orbit, a halo orbit around L2, the second Lagrange point of the Sun-Earth system the radiation environment, mainly consisting of solar and cosmic protons, electrons and He-ions, could affect the science performance. Furthermore as additional contribution the unfocused hard X-ray background is taken into account. It is important to understand and estimate the expected instrumental background and to investigate measures, like design modifications or analysis methods, which could improve the expected background level in order to achieve the challenging scientific requirement of < 5×10−3 cts/cm2/keV/s. For that purpose, the WFI background working group is investigating possible approaches, which will also be subject to technical feasibility studies. Finally an estimate of the WFI instrumental background for a proposed combination of design optimization and background rejection algorithm is given, showing that WFI is compliant with science background requirements.
eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the main instrument onboard the Russian/German "Spectrum-Roentgen-Gamma" (SRG) mission which will be operated in an L2 orbit. It will perform the first imaging all-sky survey in the medium energy band. The main scientific goals are a) to detect the hot intergalactic medium of ~100 thousand galaxy clusters and groups and hot gas in filaments between clusters to map out the large scale structure in the Universe for the study of cosmic structure evolution, b) to detect systematically all obscured accreting Black Holes in nearby galaxies and many (up to 3 Million) new, distant active galactic nuclei, and c) to study in detail the physics of galactic X-ray source populations, like pre-main sequence stars, supernova remnants and X-ray binaries. The eROSITA flight model was assembled in 2016 and has successfully passed all acceptance tests on instrument level in the facilities of MPE and IABG in Germany. eROSITA was shipped to NPOL (SRG prime contractor) in January 2017. Currently (May 2018) eROSITA has been integrated on the SRG spacecraft and has successfully passed all functional tests. eROSITA is now awaiting its launch from the Baikonur cosmodrome in spring 2019. The launcher will be a PROTON with an upper stage BLOK-DM.
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 German X-ray telescope eROSITA will perform the first imaging all-sky survey in the medium energy range up to 10 keV with unprecedented spectral and angular resolution. The launch of eROSITA onboard of the Russian Spectrum- Röntgen-Gamma satellite into an orbit around the L-2 lagrangian point is foreseen in 2016. Even tough the L-2 space environment can be considered free of orbital debris, the presence of extraterrestrial meteoroids in the interplanetary space implies a certain hazard for the eROSITA pnCCDs, as experienced by both pn and MOS cameras onboard XMM-Newton. In this paper we address this question and investigate the response of the optical blocking filter to hypervelocity impacts.
Due to the particle background and radiation damage in orbit, the CCDs aboard X-ray astronomical satellites (such as eROSITA) tend to degrade in their performance, especially in the charge transfer inefficiency (CTI).
The on-board Calibration Source based on Fe-55 will be used to monitor the CTI and the gain. It provides Mn-Kα (5.89 keV) and Mn-Kβ (6.49 keV) lines (accompanied by Auger electrons), but also the Al-K (1.49 keV) and Ti-Kα (4.51 keV) and Ti-Kβ (4.93 keV) fluorescence lines from a target made of aluminum and a contribution of titanium. Measurements with the Calibration Source will be used to compare the on-board CTI with the CTI measured on ground and to modify the CTI correction.
We summarize the design and trade-off analysis of the internal eROSITA calibration source and present results obtained with TRoPIC (eROSITA prototype camera) at the PANTER X-ray test facility in the energy range 0.5−250 keV. Various geometries have been tested to optimize the homogeneity of the calibration lines in the focal plane, the overall efficiency, and the line ratios between Mn-K and Al-K.
Additionally, multi-component target materials (titanium and silver in addition to aluminum) have been tested. Moreover, the required source strength has been determined to obtain enough photons from the source after several years when radiation damage becomes significant and the source intensity has decayed (T1/2 ~ 999 d). Finally, also measurements to determine the electron content have been performed.
We developed and tested X-ray PNCCD focal plane detectors for the eROSITA (extended ROentgen Survey with an
Imaging Telescope Array) space telescope. General scientific goal of the eROSITA project is the exploration of the X-ray
universe in the energy band from about 0.2 keV up to 10 keV with excellent energy, time, and spatial resolution in
combination with large effective telescope areas. The observational program divides into an all-sky survey and pointed
observations. The mission duration is scheduled for 7.5 years. The German instrument will be launched in near future to
the Lagrange point L2 on the Russian satellite SRG. The detection of single X-ray photons with precise information
about their energy, angle of incidence and time is accomplished for eROSITA by an array of seven identical and
independent PNCCD cameras. Each camera is assigned to a dedicated mirror system of Wolter-I type. The key
component of the camera is a 5 cm • 3 cm large, back-illuminated, 450 μm thick and fully depleted frame store PNCCD
chip. This chip is a further development of the sensor type that is in operation as focal plane detector on the XMMNewton
satellite since launch in 1999 to date. Development and production of the CCDs for the eROSITA project were
performed by the MPI Halbleiterlabor, as already in the past for the XMM-Newton project. According to the status of
the project, a complete design of the seven flight cameras including the camera electronics and the filter wheel has been
developed. Various functional and performance tests have been accomplished for a detailed characterization of the
eROSITA camera system. We focus here especially on the focal plane detector design and the performance of the
detectors, which are essential for the success of the X-ray astronomy space project.
eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the core instrument on the Russian
Spektrum-Roentgen-Gamma (SRG) mission which is scheduled for launch in 2013. eROSITA will perform an all-sky
survey lasting four years, followed by a phase of three years for pointed observations. eROSITA consists of seven
identical Mirror Modules, each equipped with 54 Wolter-I shells with an outer diameter of 360 mm. This would provide
an effective area of ~1500 cm2 at 1.5 keV and an on axis PSF HEW of 15 arcsec resulting in an effective angular
resolution of 28 arcsec averaged over the field of view. In the focus of each mirror module, a fast frame-store pn-CCD
provides a field of view of 1°in diameter. In this paper we report on the instrument development and its status only.
eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the core instrument on the Russian Spektrum-Roentgen-Gamma (SRG) mission which is scheduled for launch in late 2012. eROSITA is fully approved and funded by the German Space Agency DLR and the Max-Planck-Society. The instrument development is in phase C/D since fall 2009. The design driving science is the detection 100.000 Clusters of Galaxies up to redshift z ~1.3 in order to study the large scale structure in the Universe and test cosmological models, especially Dark Energy. This will be accomplished by an all-sky survey lasting for four years plus a phase of pointed observations. eROSITA consists of seven Wolter-I telescope modules, each equipped with 54 Wolter-I shells having an outer diameter of 360 mm. This would provide an effective area of ~1500 cm2 at 1.5 keV and an on axis PSF HEW of 15 arcsec resulting in an effective angular resolution of 28 - 30 arcsec, averaged over the field of view. In the focus of each mirror module, a fast frame-store pn-CCD provides a field of view of 1° in diameter.
The next large NASA mission in the field of gamma-ray astronomy, GLAST, is scheduled for launch in 2007. Aside from the main instrument LAT (Large-Area Telescope), a gamma-ray telescope for the energy range between 20 MeV and > 100GeV, a secondary instrument, the GLAST burst monitor (GBM), is foreseen. With this monitor one of
the key scientific objectives of the mission, the determination of the high-energy behaviour of gamma-ray bursts and transients can be ensured. Its task is to increase the detection rate of gamma-ray bursts for the LAT and to extend the energy range to lower energies (from ~10 keV to ~30 MeV). It will provide real-time burst locations over a wide FoV with sufficient accuracy to allow repointing the GLAST spacecraft. Time-resolved spectra of many bursts recorded with LAT and the burst monitor will allow the investigation of the relation between the keV and the MeV-GeV emission from GRBs over unprecedented seven decades of energy. This will help to advance our understanding of the mechanisms by which gamma-rays are generated in gamma-ray bursts
The spectrometer SPI, one of the two main instruments of the INTEGRAL spacecraft, has strong capabilities in the field of Gamma-Ray Burst (GRB)detections. In its 16° field of view (FoV) SPI is able to trigger and to localize GRBs. With its large anticoincidence shield (ACS) of 512 kg of BGO crystals SPI is able to detect GRBs quasi omnidirectionally with a very high sensitivity. The ACS GRB alerts will provide GRB arrival times with high accuracy but with no or very rough positional information. The expected GRB detection rate in SPI's FoV will be one per month and for the ACS around 300 per year. At MPE two SPI software contributions to the real-time INTEGRAL burst-alert system (IBAS) at the INTEGRAL science data centre ISDC have been developed. The SPI-ACS branch of IBAS will produce burst alerts and light-curves with 50 ms resolution. It is planned to use ACS burst alerts in the 3rd interplanetary network. The SPI-FoV branch of IBAS is currently under development at MPE. The system is using the energy and timing information of single and multiple events detected by the Germanium-camera of SPI. Using the imaging algorithm developed at the University of Birmingham the system is expected to locate strong bursts with an accuracy of better than 1°.
One of the scientific objectives of the GLAST mission is the study of
gamma-ray bursts (GRBs) which will be measured by the Large-Area Telescope, the main instrument of GLAST, in the energy range from ~20 MeV to ~300 GeV. In order to extend the energy measurement towards lower energies a secondary instrument, the GLAST Burst Monitor (GBM)
will measure GRBs from ~10 keV to ~25 MeV and will thus allow the investigation of the relation between the keV and the MeV-GeV emission from GRBs. The GBM consists of 12 circular NaI crystal discs and 2 cylindrical BGO crystals. The NaI crystals are optimized for gamma radiation from ~10 keV to ~1 MeV and the BGO crystals from
~150 keV to ~25 MeV. The NaI crystals are oriented in such a way that the measured relative counting rates allow a rapid determination of the position of a gamma-ray burst within a wide FoV of ~8.6 sr. This position will be communicated within seconds to the LAT which may then be reoriented to observe the long-lasting high-energy gamma-ray emission from GRBs. This will allow the exploration of the unknown aspects of the high-energy burst emission and their connection with the well-known low-energy emission. Another important feature of the GBM is its high time resolution of ~10 microseconds for time-resolved gamma-ray spectroscopy.
ESA's INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) will be launched in October 2002. Its two main instruments are the imager IBIS and the spectrometer SPI. Both emply coded apertures to obtain directional information on the incoming radiation. SPI's detection plane consists of 19 hexagonal Ge detectors, its coded aperture has 63 tungsten-alloy elements of 30 mm thickness.
SPI, the Spectrometer on board the ESA INTEGRAL satellite, to be launched in October 2002, will study the gamma-ray sky in the 20 keV to 8 MeV energy band with a spectral resolution of 2 keV for photons of 1 MeV, thanks to its 19 germanium detectors spanning an active area of 500 cm2. A coded mask imaging technique provides a 2° angular resolution. The 16° field of view is defined by an active BGO veto shield, furthermore used for background rejection. In April 2001 the flight model of SPI underwent a one-month calibration campaign at CEA in Bruyères le Châtel using low intensity radioactive sources and the CEA accelerator for homogeneity measurements and high intensity radioactive sources for imaging performance measurements. After integration of all scientific payloads (the spectrometer SPI, the imager IBIS and the monitors JEM-X and OMC) on the INTEGRAL satellite, a cross-calibration campaign has been performed at the ESA center in Noordwijk. A set of sources has been placed in the field of view of the different instruments in order to compare their performances and determine their mutual influence. We report on the scientific goals of this calibration activity, and present the measurements performed as well as some preliminary results.
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