On the design of wide-field x-ray telescopes
X-ray telescopes having a relatively wide field-of-view and spatial resolution vs. polar off-axis angle curves much flatter than the parabolic dependence characteristic of Wolter I designs are of great interest for surveys of the X-ray sky and potentially for study of the Sun's X-ray emission. We discuss the various considerations affecting the design of such telescopes, including the possible use of polynomial mirror surface prescriptions, a method of optimizing the polynomial coefficients, scaling laws for mirror segment length vs. intersection radius, the loss of on-axis spatial resolution, and the positioning of focal plane detectors.
Xenia: cosmo-chemical evolution of the Universe
Xenia is a medium-sized mission optimized to study cosmic reionization, cluster formation and evolution, and the WHIM, following cosmo-chemical evolution from the very earliest times to the present. Reconstructing the cosmic history of metals, from the first population of stars to the processes involved in the formation of galaxies and clusters of galaxies, is a key observational challenge. Most baryons reside in diffuse structures, in (proto)-galaxies and clusters of galaxies, and are predicted to trace the vast filamentary structures created by the ubiquitous Dark Matter. X-ray spectroscopy of diffuse matter has the unique capability of simultaneously probing a broad range of elements (C through Fe) in all their ionization stages and all binding states (atomic, molecular, and solid), and thus provides a model-independent survey of the metals. Xenia - proposed to the Astro2010 Decadal Survey - will combine cryogenic imaging spectrometers and wide field X-ray optics with fast repointing to collect essential information from three major tracers of metals: Gamma Ray Bursts (GRBs), Galaxy Clusters, and the Warm-Hot Intergalactic Medium (WHIM). We give an overview of the mission and discuss the instruments designed to carry out these observations.
Design, Construction, And Performance Of The ROSAT High-Resolution X-Ray Mirror Assembly
A grazing incidence telescope has been developed for the x-ray astronomy satellite ROSAT including a verification model and a flight model. The telescope consists of a fourfold nested Wolter type I mirror assembly of 84-cm front aperture and 240-cm focal length. The verification model has been built and fully assembled to a telescope. Full aperture x-ray measurements performed in our 130-m long-beam facility are pesented and successfully compared with model predictions based on mirror metrology data. An energy independent angular resolution of 4-sec of arc half-energy width for the encircled point spread function and a mirror surface microroughness of <3 Å have been achieved. Metrology of the actual flight mirrors (although not yet assembled to a telescope) indicates an even better performance.