Design and development of the eROSITA x-ray mirrors

Abstract

MPE will provide the X-ray Survey Telescope eROSITA [5] for the Russian Spektrum-Roentgen-Gamma Mission [4] to be launched in 2011. The design of the X-ray mirror system is based on that of ABRIXAS: The bundle of 7 mirror modules with the short focal length of 1600 mm makes it still a compact instrument while, however, its sensitivity in terms of effective area, field-of-view, and angular resolution shall be largely enhanced with respect to ABRIXAS. The number of nested mirror shells increases from 27 to 54 compared to ABRIXAS thus enhancing the effective area in the soft band by a factor of six. The angular resolution is targeted to be 15 arc seconds half-energy width (HEW) on-axis resulting in an average HEW of 26 arc seconds over the 61 arc minutes field-of-view (FoV). The instrument's high grasp of about 1000 cm 2 deg 2 in the soft spectral range and still 10 cm 2 deg 2 at 10 keV combined with a survey duration of 4 years will generate a new rich database of X-ray sources over the whole sky. As the 7 mirror modules are co-aligned eROSITA is also able to perform pointed observations.

The eROSITA x-ray baffle

“…The X-ray baffle is designed to block the light paths of single reflections (stray light), in particular from the mirror's hyperbola part [2]. It needs a special design adapted to the optical parameters of the mirror module: The aperture ratio of up to 4.5 and the large field-of-view requires that the baffling of single reflections has to happen close to the mirror shells; the baffle has to reach inside the envelope of the mirror spider.…”

“…The X-ray telescope of eROSITA [3] consists of 7 identical and co-aligned mirror modules, each with 54 nested Wolter-1 mirror shells [1,2]. An X-ray baffle in front of each mirror entrance protects against X-ray stray light from single reflections from the hyperbola part of the Wolter mirrors.…”

Status of the eROSITA Telescope testing and calibrating the x-ray mirror assemblies

“…The thermal behavior of the instrument corresponds quite well to the thermal modeling made before. The manufacturing of the Mirror Modules and theX-ray Baffles, both long lead items, went on smoothly in parallel [5,6]. The status of the integration of the mirror shells into the flight modules is displayed graphically in Figure 10.…”

The calibration and testing of the eROSITA X-ray mirror assemblies

“…In the case of eROSITA [3,4,5] 7 co-aligned 54 shell Wolter-1 mirror modules [6,7,8] with a focal length of 1600mm are mounted in the carbon fiber telescope structure together with their corresponding CCD cameras [9,10]. The telescope is mainly designed to work as a survey telescope with the added capability of working in a pointing mode after the 4 years of the all-sky survey have been completed.…”