The abbreviation “eXTP” represents the enhanced x-ray timing and polarimetry, which is a key science mission initiated by the Chinese scientists, designed to study the state of matter under extreme conditions of density, gravity and magnetism [1]. Various payloads would be on board of the satellite. The SFA, namely the spectroscopy focusing array, consisting of nine identical x-ray telescopes working in the energy range of 0.5-10 keV, will be the focus here [1]. SFA has a field-of-view of 12 arcmin for each and a collecting area of 900 cm² and 550 cm² for each at 2 keV and 6 keV respectively [1].

This paper starts with a brief introduction of the general optics, and then goes across some important design aspects. It covers contents from the structural and thermal designs to the CAE analyses as well as the current status. The large diameter and huge focal length of the optics will definitely bring big issues to the robustness of the carrying structure under the severe conditions given by the launcher.

According to the current design, the mirror assembly will have 3 feet and 24 spokes. Vibration tests were already performed on a few prototypes by IHEP, and a preliminary evaluation on the feasibility of the design has been achieved. It clearly stated that the current design with only a single spider can probably survive the vibration tests assuming a compromised test condition somewhere. CAE models were adjusted thereafter to match the test results, which could be used for further assessments in a near future.

ESA’s Athena mission will use silicon pore optics, in which the optics assembly consists of pairs of mirror plates stacked into mirror modules. This paper presents a study of the angular resolution of Athena, using several candidate variants of mirror curvature and wedging. Results were achieved by ray-tracing these variants of Athena’s optics with the ray-tracing software SPORT.

The study shows that all polynomial variants yield a PSF below 1” on-axis, at all energies between 0.1 and 12 keV. The secondary-only polynomial variants perform best, for both on- and off-axis point sources. Of these variants, the wedging 0/2 variant is shown to generally yield superior angular resolution at higher energies, the -1/1 variant at lower energies.

A ray-tracing analysis using the Crab Nebula as an observation target was also performed. A 2D Fourier analysis was applied to the resulting focal plane responses to determine their angular resolution. This analysis indicates the angular resolution of all polynomial variants to be below 1”, at all but the highest energies. It also shows, though to a lesser extent, that the secondary-only polynomial variants perform best in most circumstances. Nevertheless, this second analysis requires further investigation for a more conclusive outcome.

The next generation of Imaging Atmospheric Cherenkov Telescope will explore the uppermost end of the Very High Energy domain up to about few hundreds of TeV with unprecedented sensitivity, angular resolution and imaging quality.

To this end, the Italian National Institute of Astrophysics (INAF) is currently developing a scientific and technological telescope prototype for the implementation of the Cherenkov Telescope Array (CTA) observatory. The Italian ASTRI program foresees the full design, development, installation and calibration of a Small Size 4-meter class Telescope, adopting an aplanatic, wide-field, double-reflection optical layout in a Schwarzschild-Couder configuration.

In this paper we discuss about the technological solutions adopted for the telescope and for the mirrors. In particular we focus on the structural and electro-mechanical design of the telescope, now under fabrication. The results on the optical performance derived from mirror prototypes are here described, too.

Silicon Pore Optics is an enabling technology for future L- and M-class astrophysics X-ray missions, which require high angular resolution (~5 arc seconds) and large effective area (1 to 2 m² at a few keV). The technology exploits the high-quality of super-polished 300 mm silicon wafers and the associated industrial mass production processes, which are readily available in the semiconductor industry. The plan-parallel wafers have a surface roughness better than 0.1 nm rms and are diced, structured, wedged, coated, bent and stacked to form modular Silicon Pore Optics, which can be grouped into a larger optic. The modules are assembled from silicon alone, with all the mechanical advantages, and form an intrinsically stiff pore structure.

The optics design was initially based on long (25 to 50 m) focal length X-ray telescopes, which could achieve several arc second angular resolution by curving the silicon mirror in only one direction (conical approximation).

Recently shorter focal length missions (10 to 20 m) have been discussed, for which we started to develop Silicon Pore Optics having a secondary curvature in the mirror, allowing the production of Wolter-I type optics, which are on axis aberration-free.

In this paper we will present the new manufacturing process, the results achieved and the lessons learned.