Ground-based X-ray calibration of the telescopes onboard Astro-E2 satellite

摘要

Astro-E2, to be launched in early 2005, will carry five X-ray Telescopes (XRT). The design of the XRT is the same as the previous original mission Astro-E, that is a conical approximation of Wolter Type-I optics, where about 170 thin-foil reflectors are nested confocally. Some modifications from Astro-E are adopted within the severe constraints due to the policy of "re-build" instruments. One of the major changes is the addition of pre-collimators for the stray light protection. Several modifications on the fabrication processes are also made. The replication glass mandrels are screened carefully, which is expected to reduce the figure error of replicated reflectors. We thus expect better performance than Astro-E especially in imaging capability. In order to qualify the performance of the Astro-E2 XRT, we have started ground calibration program of XRT at 30 meter X-ray beam facility of the Institute of Space and Astronautical Science (ISAS). We have found positive improvements on the telescope performance from the Astro-E, which probably arise from the applied modifications. The on-axis half-power diameter (HPD) has been evaluated to be 1.6-1.7 arcmin, which is improved from the Astro-E (2.0 ～ 2.1 arcmin HPD). The on-axis effective areas of quadrants are larger than the average of Astro-E by about 5%. The on-axis effective areas of the XRT for X-ray Imaging Spectrometers (XIS) are approximately 460, 340, 260, and 190 cm~2 at energies of 1.49, 4.51, 8.04, and 9.44 keV, respectively. The present paper describes the recent results of the performance of the first flight assembly of the Astro-E2 XRT.