eROSITA Technical Performance

The eROSITA Instrument

The picture shows a schematic view of the telescope. eROSITA consists of seven identical and co-aligned X-ray Mirror Assemblies (MA) housed in a common optical bench. The supporting telescope structure consists of a system of carbon fibre honeycomb panels connecting the seven MAs on one side with the associated seven Camera Assemblies (CA) on the other side. A hexapod structure forms the mechanical interface to the S/C bus. The seven individual Telescope Modules (TM) are arranged in a hexagonal shape. Two starsensors (Sodern SED26) are mounted on eROSITA. They belong to the attitude system of the S/C but serve also for a determination of the boresight. The dimensions of the telescope structure are approximately 1.9 m (diameter) × 3.2 m (height in launch configuration, with closed front cover). The total weight of eROSITA is 808 kg (From Predehl et al. 2021).

Table 1: Basic instrument characteristics at launch (From Predehl et a. 2021).

Table 2: Energy resolution [eV] and quantum efficiencies (QE) of the eROSITA Camera Assemblies as measured on ground. “QE12346” is for cameras TM1,2,3,4,6, which have filters directly deposited onto the CCD; “QE57” is the quantum efficiency of cameras TM5 and TM7, which have their filters in the filter wheel. From Predehl et al. (2021).

Figure 1: Comparison of the Field of View average effective areas as a function of energy for eROSITA (red), Chandra ACIS-I (in 1999, dark green, and in 2020, light green), Chandra HRC-I (purple), XMM-Newton (blue), and ROSAT (brown). From Predehl et al. (2021).

Figure 2: Comparison of the grasp, defined as the product of field of view times (averaged) effective area, as a function of energy for eROSITA (red), Chandra ACIS-I (in 1999, dark green, and in 2020, light green), Chandra HRC-I (purple), XMM-Newton (blue), and ROSAT (brown). From Predehl et al. (2021).

Table 3: Some key performance parameters of the eROSITA Mirror Assemblies as calibrated on ground: The on-axis angular resolution (HEW [arcsec]) is corrected for the detector resolution. The PSF has been measured also at C-K but is omitted here because it is almost identical to Al-K. The FWHM [arcsec] is an approximate value of the mirror-detector combination. The on-axis effective areas [cm^2] were measured using the standard setup. Errors are 1σ for PSF and 3σ for effective areas.

eROSITA response matrices based on ground calibration measurements.