Coatings for the NuSTAR mission

Abstract

The NuSTAR mission will be the first mission to carry a hard X-ray(5-80 keV) focusing telescope to orbit. The optics are based on the use of multilayer coated thin slumped glass. Two different material combinations were used for the flight optics, namely W/Si and Pt/C. In this paper we describe the entire coating effort including the final coating design that was used for the two flight optics. We also present data on the performance verification of the coatings both on Si witness samples as well as on individual flight mirrors.

NuSTAR observatory science operations: on-orbit acclimation

“…Figure 9. Contour image of target positions on the focal plane normalized to the centroid of the motion in each observation (placed at [6,6]). The contour has a logarithmic scale to show the extent of the relative motion.…”

“…9 shows a contour image of the relative motion of the target position on the focal plane taken from over 800 observations (>3x10 6 measurements) during the first two years of the mission. The relative positions are normalized with the centroids for each observation placed at [6,6]. The plot has a logarithmic scale with 90% of all target position measurements within the red contour area.…”

“…The X-ray optics and detector benches are separated by a stiff mast that includes a mechanism with the capability of making small adjustments to optimize the location of the optical axis on the focal plane detectors (see Fig.1). The X-ray optics bench consists of two Wolter-I conical approximation 3 mirror modules, each with 133 shells coated with multiple layers of W/Si and Pt/C, limiting the highest efficient reflectivity to the Pt 78.4 keV K-edge 4,5,6 . The focal plane bench is mounted on the spacecraft bus and consists of two independent solid state photon counting detector modules (FPMA & B), each with a 2x2 array of CdZnTe (CZT) crystal detectors, surrounded by CsI anti-coincidence shielding.…”

NuSTAR on-ground calibration: II. Effective area

“…The MRD tracks run-to-run variations in coating chamber parameters and coating nonuniformity based on specular reflectivity measurements carried out at RaMCaF and DTU Space. As such, the MRD replaces the multilayer design presented by Christensen et al 4 and summarized in Table 1.…”

“…The on-ground calibration of the two multilayer coated flight optics was carried out at the Rainwater Memorial Calibration Facility for X-ray optics (RaMCaF) 2,3 at Nevis Laboratories in New York. The multilayer coating was laid down at the Technical University of Denmark (DTU Space) 4 .…”