Groundbreaking X-ray optics will enable future observatories

Wolter-I mirror segment with a thickness of 0.6 mm. This mirror has a dimension of approximately 100 mm by 100 mm. Tens of thousands of mirror segments like this one will be aligned and integrated to make an assembly to achieve several m2 of effective area. Credit: Bill Hrybyk

An X-ray telescope is characterized by four parameters: angular resolution, effective area, mass, and production cost. Researchers at NASA GSFC have developed a new X-ray mirror technology that is expected to improve one or more of these parameters by at least an order of magnitude, compared to the mirrors currently employed on missions such as the Chandra X-ray Observatory and the Nuclear Spectroscopic Telescope Array (NuSTAR).

This mirror technology combines a polishing process used for fabricating optics of the highest quality with use of monocrystalline silicon—a material used in the semiconductor industry. Monocrystalline silicon is free of internal stress and thereby enables development of extremely thin (less than 1 mm) and lightweight (areal density less than 2.5 kg/m2) mirrors. The GSFC team has been working to perfect this technology since 2011, and in 2016 they developed a process to make Wolter-I (parabolic or hyperbolic) mirrors as thin as 0.5 mm with figure quality better than 3 arcsec—a tenfold improvement over the NuSTAR mirrors. In parallel, the team developed a bonding process that preserves the figure and alignment of these thin mirrors, while enabling them to sustain a typical space launch vibration environment.

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