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The Soft Gamma-ray Detector (SGD) is a Si/CdTe Compton telescope surrounded by a thick BGO active shield and is scheduled to be onboard the ASTRO-H satellite when it is launched in 2015. The SGD covers the energy range from 40 to 600 keV with high sensitivity, which allows us to study nonthermal phenomena in the universe. The SGD uses a Compton camera with the narrow field-of-view (FOV) concept to reduce the non-Xray background (NXB) and improve the sensitivity. Since the SGD is essentially a nonimaging instrument, it also has to cope with the cosmic X-ray background (CXB) within the FOV. The SGD adopts passive shields called “fine collimators” (FCs) to restrict the FOV to ≤ 0.6° for low-energy photons (≤ 100 keV), which reduces contamination from CXB to less than what is expected due to NXB. Although the FC concept was already adopted by the Hard X-ray Detector onboard Suzaku, FCs for the SGD are about four times larger in size and are technically more difficult to operate. We developed FCs for the SGD and confirmed that the prototypes function as required by subjecting them to an X-ray test and environmental tests, such as vibration tests. We also developed an autocollimator system, which uses visible light to determine the transmittance and the optical axis, and calibrated it against data from the X-ray test. The acceptance tests of flight models started in December 2013: five out of six FCs were deemed acceptable, and one more unit is currently being produced. The activation properties were studied based on a proton-beam test and the results were used to estimate the in-orbit NXB.

The thirty-meter X-ray pencil beam line at the Institute of Space and Astronautical Science (ISAS) was utilized for ground-based calibrations of X-ray telescopes (XRTs) onboard the ASTRO-D, the ASTRO-E and the ASTRO- E2 satellites. Recent upsizing or downsizing of XRT required upgrade of the ISAS beam line. We replaced a vacuum chamber in which the stages had been installed by a new cylindrical chamber whose diameter and length are 1.8 m and 11.3 m, respectively. Stages on which a telescope and detectors had been mounted were also replaced. At same time, a new CCD consists of 1240×1152 pixels whose size are 22.5×22.5 μm was introduced. The detector stage can be moved along the X-ray beam in the vacuum chamber, which allows us to change the distance between the sample and the detectors from 0.7 m to 9 m. The two stages can move in at least 500×500 mm2 of square in the plane normal to the X-ray beam. The pitching of some moving axes are measured at 60 arcsec at most. The others are no more than about 30 arcsec. From April 2013, the ASTRO-H Soft X-ray telescopes (SXTs) have been calibrated at the new ISAS beam line.

We report recent progresses on the fabrication of pre-collimators (PCs). The PCs are designed to mitigate stray lights for X-ray telescopes to be onboard ASTRO-H. Each PC consists of cylindrical aluminum shells (blades) wiht varying radii of 60-225 mm, alignment frames to guilde the blade positions, and the bade housing body. The alignment frame and the housing are made of Aluminum 6061 and 7075 alloy, respectively. Heat-forming process is introduced to the production to stabilize the blade shape in orbit. Precise curvature of radius (tolerance of 1mm) and the linearity along with the direction of incident X-rays (P.V. < 20 microns) ensure that the blades do not obscure the telescope aperature. Each PC blade is placed precisely on top of the respective reflector mirror shell to reduce off-axis X-ray photons that leads to a "ghost" image within the detector field of view. In September 2010, the PC design--its height, thickness, and material of blades--was fixed and we produced the engineering model (EM) for the Soft X-ray Telescopes (SXTs). Since then, vibration tests for the EM PC unit are carried out twice, verifying that the PC has sufficient structural strength to withstand severe conditions during its launch. The EM PC is also installed onto the SXT mirror housing fabricated at the NASA's GSFC to validate our PC assembly method without any loss of thetelescope's effective aperture area. Since August 2011, we have been manusfacturing the PC blades for the flight models. We hereby show the manufacturing processes and also results of stray-light measurement without PCs for the SXT EM (obtained at ISAS 30m beamline facility) and the HXT FM (obtained at SPring-8 synchrotron radiation facility).

The ASTRO-H Hard X-ray Telescope (HXT) to cover hard X-rays up to 80 keV is thin-foil, multi-nested conical optics with depth-graded Pt/C multilayer. The reflectors are made of heat-formed aluminum substrate of the thickness gauged of 200 μm of the alloy 5052, followed by epoxy replication on Pt/C-sputtered smooth Pyrex cylindrical mandrels to acquire the X-ray reflective surface. The epoxy layer is 20 μm depth. In this paper, we report a thermal stress test of the reflectors of the HXT. The reflectors can experience in various temperature environment either in ground or in space. The temperature range can be as wide as several tens degrees in space dependently on the thermal design of the telescope system. We kept the reflectors in the three different temperatures at -5, 50 and 60 degrees, respectively, for a week. It is found that the surface of the reflectors at 60 degrees or higher temperature were significantly changed. The change appears as wrinkles with a typical scale length of a few tens micron meters. It is noticed that the scale length is equivalent to the depth of the epoxy layer, suggesting the existence of the epoxy layer causes the change in the scale length. No changes on the surface were observed from the -5 and 50 degree samples. No change on X-ray reflectivity was also detected from them.

The Japanese ASTRO-H mission, planned to be launched in 2014, will carry several instruments for covering a wide energy range from a few keV to 600 keV. Among them there are four thin-foil-nested Wolter-I X-ray telescopes. Two of them are Soft X-ray Telescopes (SXTs) covering up to ~12 keV. Each of them focuses an image on the focal plane detectors of the CCD camera (SXI) and the calorimeter (SXS-XCS), respectively. In 2011, we performed a ground calibration of a quadrant engineering model (EM) of SXT that was fabricated at MASA's Goddard Space Flight Center (GSFC). The ground calibration was made with a combination of the measurements at the GSFC and Institute of Space and Astronautical Science (ISAS) facilities. In this paper we report the results of the calibration at the ISAS 30m beamline facility. We used a raster san method with a pencil beam at the baseline length of 30m. An effective area and angular resolution of the EM quadrant were measured. The effective area is 147 cm 2 at 1.49 keV and 116 cm 2 at 4.51 keV, respectively, while the angular longer by ~20mm from nominal length. We also measured imaging performance in separate parts of nested mirrors. The angular resolution of parts at outer radius is larger than those at inner radius, and the quadrant have different focal lengths in radius.

X-ray reflection mirror of the Soft X-ray Telescope onboard ASTRO-H was coated by gold thin layer. Gold have M-shell X-ray absorption edge around 2 keV which is included in the energy band covered with the focal plane detector such as Soft X-ray Imager and Soft X-ray Spectrometer. It is important to make response function taken int account the Au M-dege structure especially for the Soft X-ray Spectrometer because It has unprecedented high energy resolution of 5 eV from 0.3 to 12 keV. We performed the detailed measurements of of reflectivity of the mirror using reflectometer in the synchrotron radiation facility KEK PF BL-11B from Nov. 29, 2011 to Dec. 5. X-ray beam of BL–11B was monochromatized to E/deltaE of 5000 by Double crystal monochromator using Si(111). We obtained the reflectivity at the grazing incident angles of 1.0, 1.2, and 1.4 degrees. While the energy pitch was set to be 2 eV in the 2.1–4.1 keV band, the reflectivity in the 2.2–2.35 keV band was also measured in detail with the energy pitch of 0.25 eV. We report the results and optical parameters of the SXT mirror such as reflectivity, and roughness calculated from the measurements.

We have been developing a thin-foil-nested X-ray telescope (XRT) for the Japanese X-ray astronomy satellites since ASCA launched in 1993. The thin-foil-nested XRT is advantageous in realizing high throughput with a light weight, whilst its angular resolution is poorer than other mirrors using, for example, a polished thick glass substrate onboard Chandra. We have investigated causes of image degradation of our XRT, and have identified them as figure error and positioning error of the reflectors. Since the latter dominates the entire error budget, we first attempted to improve the positioning error, and adopted the following two methods. First, we substituted an alignment plate for the alignment bar. The alignment plate incorporates the independently movable four alignment bars adopted for ASCA and Suzaku into a single plate. In practice, we allocated a pair of the plate in each slot, and after inserting all the reflectors, we shifted one of the plates radially to tightly hold the reflectors. Second, we have manufactured a partially replicated foil in which reflecting material (Au) is not applied to the axial edges of the foils in order to control the foil position by the edges of the reflectors whose thickness variation is within 2 μm. After these improvements on the positioning error, we moved onto the figure error issue. With X-ray and laser profilometer measurements, we found that the figure error increased in a area closer to the azimuthal edges of the reflector. After considerable struggle for improvement, we finally decided to produce a long reflector and to cut both azimuthal edges. Thanks to these new devices, we have reduced the positioning error from 1.5 arcmin to 0.66. Furthermore, we have successfully produced 40-pairs of reflectors whose figure error is less than 0.8 arcmin. Incorporating these reflectors into a mirror housing, we have measured the XRT performance in the 30 m beamline facility at ISAS/JAXA, and confirmed to achieve an angular resolution of 1.08 arcmin in half-power diameter. The effective area is measured to be 14.0 cm 2 , which is ~90% of the designed value. Note that this number is significantly enhanced from ~80% in the Suzaku XRT, which is a by-product of the improvement of the angular resolution.

When a free-space optical beam propagates through the atmosphere it experiences deterioration and deformation of its wave-front caused from small scale, randomly localized changes in the atmospheric index of refraction. This results in beam wander and scintillation effects which can reduce the link availability and may introduce burst errors. This paper outlines experimental work on a free-space optical (FSO) communication system which connects an optical beam directly to a single-mode fiber (SMF) without any optical-to-electrical (O-E) conversion. In order to effectively couple the 1550 nm transmitted optical beam to a SMF it is necessary to be able to track and control the beam angle-of-arrival (AOA) changes. To achieve this, we have developed an optical antenna which uses a fine positioning mirror (FPM) capable of performing high-speed beam tracking and steering thus reducing to a great extent the optical power fluctuations of the received beam coupled to the SMF. This optical power fluctuation is partly a result of beam angle-of-arrival fluctuations caused by atmospheric turbulence. In our experiments we have tried to measure and quantify the magnitude of atmospheric turbulence experienced by an optical beam propagating through the atmosphere. First we demonstrate the relation between the AOA fluctuations and the frequency characteristics of the scintillation effects for a free-space optical beam propagating through a turbulent atmosphere. We use this information to determine the optimum antenna FPM tracking speed for improved performance and error free transmission. The results in the improved fiber received power as well as continuous error free transmission are presented.