Integration of the ATHENA Mirror Modules: Development Status of the Indirect and Direct X-Ray Methods

Within the ATHENA optics technology plan, activities are on-going for demonstrating the feasibility of the mirror module integration. Each mirror module has to be accurately attached to the mirror structure support by means of three isostatic mounts ensuring minimal distortion under environmental loads. This work reports on the status of one of the two parallel activities initiated by ESA to address this demanding task. In this study awarded to the industrial consortium, the integration relies on optical metrology and direct X-ray alignment. For the first or "indirect" method the X-ray alignment results are accurately referenced, by means of a laser tracking system, to optical fiducial targets mounted on the mirror modules and finally linked to the mirror structure coordinate system. With the second or "direct" method the alignment is monitored in the X-ray domain, providing figures of merit directly comparable to the final performance. The paper updates on the laser tracking characterization results of 2 mirror modules, performed at PTB's X-ray Parallel Beam Facility (XPBF 2.0) at BESSY II. The same 2 mirror modules have then been co-aligned and integrated in a technology demonstrator, with performance verified in full illumination at Panter. The paper provides an overview of the results obtained from the technology development activities.