The Solar Optical Telescope (SOT) aboard Solar-B satellite (Hinode) is designed to perform high-precision photometric and polarimetric observations of the solar lower atmosphere in visible light spectra (388--668 nm) with a spatial resolution of 0.2 to 0.3 arcsec. The SOT consists of two components; the optical telescope assembly (OTA) consisting of a 50-cm aperture Gregorian telescope with a collimating lens unit and an active tip-tilt mirror for an image-stabilization and an accompanying focal plane package (FPP) housing two filtergraphs and a spectro-polarimeter. Since its first-light observation on 25 Oct. 2006, the image-stabilization system has been working with performance better than 0.01 arcsec rms and the SOT has been continuously providing unprecedented solar data of high spatial resolution. Since the opto-mechanical and -thermal performance of the OTA is crucial to attain unprecedented high-quality solar observations, we here describe in detail the instrument design and on-orbit diffraction-limit performance of the OTA, the largest state-of-the-art solar telescope yet flown in space.
A 1.5-m class aperture Solar Ultra-violet Visible and IR telescope (SUVIT) and its instruments for the Japanese next space solar mission SOLAR-C  are under study to obtain critical physical parameters in the lower solar atmosphere. For the precise magnetic field measurements covering field-of-view of 3 arcmin x3 acmin, a full stokes polarimetry at three magnetic sensitive lines in wavelength range of 525 nm to 1083 nm with a four-slit spectrograph of two dinesional image scanning mechanism is proposed: one is a true slit and the other three are pseudo-slits from integral field unit (IFU). To suit this configuration, besides a fiber bundle IFU, a compact mirror slicer IFU is designed and being developed.<p> </p>Integral field spectroscopy (IFS), which is realized with IFU, is a two dimensional spectroscopy, providing spectra simultaneously for each spatial direction of an extended two-dimensional field. The scientific advantages of the IFS for studies of localized and transient solar surface phenomena are obvious. There are in general three methods  to realize the IFS depending on image slicing devices such as a micro-lenslet array, an optical fiber bundle and a narrow rectangular image slicer array.<p> </p>So far, there exist many applications of the IFS for ground-based astronomical observations . Regarding solar instrumentations, the IFS of micro-lenslet array was done by Suematsu et al. , the IFS of densely packed rectangular fiber bundle with thin clads was realized  and being developed for 4-m aperture solar telescope DKIST by Lin  and being considered for space solar telescope SOLAR-C by Katsukawa et al. , and the IFS with mirror slicer array was presented by Ren et al.  and under study for up-coming large-aperture solar telescope in Europe by Calcines et al. <p> </p>From the view point of a high efficiency spectroscopy, a wide wavelength coverage, a precision spectropolarimetry and space application, the image slicer consisting of all reflective optics is the best option among the three. However, the image slicers are presently limited either by their risk in the case of classical glass polishing techniques (see Vivès et al.  for recent development) or by their optical performances when constituted by metallic mirrors. For space instruments, small sized units are much advantageous and demands that width of each slicer mirror is as narrow as an optimal slit width (< 100 micron) of spectrograph which is usually hard to manufacture with glass polishing techniques. On the other hand, Canon is developing a novel technique for such as high performance gratings which can be applicable for manufacturing high optical performance metallic mirrors of small dimensions.<p> </p>For the space-borne spectrograph of SUVIT to be aboard SOLAR-C, we designed the IFS made of a micro image slicer of 45 arrayed 30-micron-thick metal mirrors and a pseudo-pupil metal mirror array re-formatting three pseudo-slits; the design is feasible for optical configuration sharing a spectrograph with a conventional real slit. According to the optical deign, Canon manufactured a prototype IFU for evaluation, demonstrating high performances of micro image slicer and pupil mirrors; enough small micro roughness for visible light spectrographs, sharp edges for efficient image slices, surface figure for high image quality, etc. In the following, we describe the optical design of IFU feasible for space-borne spectrograph, manufacturing method to attain high optical performance of metal mirrors developed by Canon, and resulted performance of prototype IFU in detail.
We present an innovative optical design for image slicer integral field unit (IFU) and manufacturing method which overcome optical limitation of metallic mirrors. Our IFU consists of micro image slicer of 45 arrayed highly-narrow flat metallic mirrors and a pseudo pupil mirror array of off-axis conic aspheres forming three pseudo slits of re-arranged slicer images. A prototype IFU demonstrates their optical quality high enough for a visible light spectrograph. The each slicer mirror is 1.58 mm in length and 30μm in width with surface roughness < 1 nm rms, edge sharpness < 0.1μm, etc. This IFU is small-sized and can be implemented in a multi-slit spectrograph without any moving mechanism and fore optics in which one slit is real and the others are of pseudo slits from the IFU. Those properties are well suitable for space-borne spectrograph to be aboard such as a next Japanese solar mission SOLAR-C.
WISH, Wide-field Imaging Surveyor for High-redshiftt, is a space mission concept to conduct very deep and widefield
surveys at near infrared wavelength at 1-5μm to study the properties of galaxies at very high redshift beyond the
epoch of cosmic reionization. The concept has been developed and studied since 2008 to be proposed for future
JAXA/ISAS mission. WISH has a 1.5m-diameter primary mirror and a wide-field imager covering 850 arcmin<sup>2</sup>. The
pixel scale is 0.155 arcsec for 18μm pitch, which properly samples the diffraction-limited image at 1.5μm. The main
program is Ultra Deep Survey (UDS) covering 100 deg<sup>2</sup> down to 28AB mag at least in five broad bands. We expect to
detect <10<sup>4</sup> galaxies at z=8-9, 10<sup>3</sup>-10<sup>4 </sup>galaxies at z=11-12, and 50-100 galaxies at z<14, many of which can be feasible
targets for deep spectroscopy with Extremely Large Telescopes. With recurrent deep observations, detection and light
curve monitoring for type-Ia SNe in rest-frame infrared wavelength is also conducted, which is another main science
goal of the mission. During the in-orbit 5 years observations, we expect to detect and monitor <2000 type-Ia SNe up to
z~2. WISH also conducts Ultra Wide Survey, covering 1000deg<sup>2</sup> down to 24-25AB mag as well as Extreme Survey,
covering a limited number of fields of view down to 29-30AB mag. We here report the progress of the WISH project
including the basic telescope and satellite design as well as the results of the test for a proto-model of the flip-type filter
exchanger which works robustly near 100K.
One of the biggest challenges in heliophysics is to decipher the magnetic structure of the solar chromosphere.
The importance of measuring the chromospheric magnetic field is due to both the key role the chromosphere
plays in energizing and structuring the outer solar atmosphere and the inability of extrapolation of photospheric
fields to adequately describe this key boundary region. Over the last few years, significant progress has been
made in the spectral line formation of UV lines as well as the MHD modeling of the solar atmosphere. It is
found that the Hanle effect in the Lyman-alpha line (121.567 nm) is a most promising diagnostic tool for weaker
magnetic fields in the chromosphere and transition region. Based on this groundbreaking research, we propose
the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) to NASA as a sounding rocket experiment, for
making the first measurement of the linear polarization produced by scattering processes and the Hanle effect
in the Lyman-alpha line (121.567 nm), and making the first exploration of the magnetic field in the upper
chromosphere and transition region of the Sun. The CLASP instrument consists of a Cassegrain telescope, a
rotating 1/2-wave plate, a dual-beam spectrograph assembly with a grating working as a beam splitter, and
an identical pair of reflective polarization analyzers each equipped with a CCD camera. We propose to launch
CLASP in December 2014.
We report science and development activities of the X-ray/EUV telescope for the Japanese Solar-C mission whose
projected launch around 2019. The telescope consists of a package of (a) a normal-incidence (NI) EUV telescope and (b)
a grazing-incidence (GI) soft X-ray telescope. The NI telescope chiefly provides images of low corona (whose
temperature 1 MK or even lower) with ultra-high angular resolution (0.2-0.3"/pixel) in 3 wavelength bands (304, 171,
and 94 angstroms). On the other hand, the GI telescope provides images of the corona with a wide temperature coverage
(1 MK to beyond 10 MK) with the highest-ever angular resolution (~0.5"/pixel) as a soft X-ray coronal imager. The set
of NI and GI telescopes should provide crucial information for establishing magnetic and gas-dynamic connection
between the corona and the lower atmosphere of the Sun which is essential for understanding heating of, and plasma
activities in, the corona. Moreover, we attempt to implement photon-counting capability for the GI telescope with which
imaging-spectroscopy of the X-ray corona will be performed for the first time, in the energy range from ~0.5 keV up to
10 keV. The imaging-spectroscopic observations will provide totally-new information on mechanism(s) for the
generation of hot coronal plasmas (heated beyond a few MK), those for magnetic reconnection, and even generation of
supra-thermal electrons associated with flares. An overview of instrument outline and science for the X-ray photoncounting
telescope are presented, together with ongoing development activities in Japan towards soft X-ray photoncounting
observations, focusing on high-speed X-ray CMOS detector and sub-arcsecond-resolution GI mirror.
HINODE, Japanese for "sunrise", is a spacecraft dedicated for observations of the Sun, and was launched in 2006 to study the Sun's magnetic fields and how their explosive energies propagate through the different atmospheric layers. The spacecraft carries the Solar Optical Telescope (SOT), which has a 50 cm diameter clear aperture and provides a continuous series of diffraction-limited visible light images from space. The telescope was developed through international collaboration between Japan and US. In order to achieve the diffraction-limited performance, thermal and structural modeling of the telescope was extensively used in its development phase to predict how the optical performance changes dependent on the thermal condition in orbit. Not only the modeling, we devoted many efforts to verify the optical performance in ground tests before the launch. The verification in the ground tests helped us to find many issues, such as temperature dependent focus shifts, which were not identified only through the thermal-structural modeling. Another critical issue was micro-vibrations induced by internal disturbances of mechanical gyroscopes and momentum wheels for attitude control of the spacecraft. Because the structural modeling was not accurate enough to predict how much the image quality was degraded by the micro-vibrations, we measured their transmission in a spacecraft-level test.
A sounding-rocket program called the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is proposed to be
launched in the summer of 2014. CLASP will observe the solar chromosphere in Ly-alpha (121.567 nm), aiming to detect
the linear polarization signal produced by scattering processes and the Hanle effect for the first time. The polarimeter of
CLASP consists of a rotating half-waveplate, a beam splitter, and a polarization analyzer. Magnesium Fluoride (MgF2) is
used for these optical components, because MgF2 exhibits birefringent property and high transparency at ultraviolet
The development and comprehensive testing program of the optical components of the polarimeter is underway using the
synchrotron beamline at the Ultraviolet Synchrotron Orbital Radiation Facility (UVSOR). The first objective is deriving
the optical constants of MgF2 by the measurement of the reflectance and transmittance against oblique incident angles for
the s-polarized and the p-polarized light. The ordinary refractive index and extinction coefficient along the ordinary and
extraordinary axes are derived with a least-square fitting in such a way that the reflectance and transmittance satisfy the
Kramers-Krönig relation. The reflection at the Brewster's Angle of MgF2 plate is confirmed to become a good polarization
analyzer at Ly-alpha. The second objective is the retardation measurement of a zeroth-order waveplate made of MgF2. The
retardation of a waveplate is determined by observing the modulation amplitude that comes out of a waveplate and a
polarization analyzer. We tested a waveplate with the thickness difference of 14.57 um. The 14.57 um waveplate worked as
a half-waveplate at 121.74 nm. We derived that a waveplate with the thickness difference of 15.71 um will work as a
half-waveplate at Ly-alpha wavelength.
We developed a prototype of CLASP polarimeter using the MgF2 half-waveplate and polarization analyzers, and
succeeded in obtaining the modulation patterns that are consistent with the theoretical prediction. We confirm that the
performance of the prototype is optimized for measuring linear polarization signal with the least effect of the crosstalk
from the circular polarization.
Two mission concepts (plan A: out-of-ecliptic mission and plan B: high resolution spectroscopic mission) have been
studied for the next Japanese-led solar mission Solar-C, which will follow the scientific success of the <i>Hinode</i> mission.
The both mission concepts are concluded as equally important and attractive for the promotion of space solar physics. In
the meantime we also had to make efforts for prioritizing the two options, in order to proceed to next stage of requesting
the launch of Solar-C mission at the earliest opportunity. This paper briefly describes the two mission concepts and the
current status on our efforts for prioritizing the two options. More details are also described for the plan B option as the
first-priority Solar-C mission. The latest report from the Solar-C mission concept studies was documented as "Interim
Report on the Solar-C Mission Concept."
We report instrument outline as well as science of the photon-counting soft X-ray telescope that we have been studying
as a possible scientific payload for the Japanese Solar-C mission whose projected launch around 2019. Soft X-rays (~1-
10 keV) from the solar corona include rich information on (1) possible mechanism(s) for heating the bright core of active
regions seen in soft X-rays (namely, the hottest portion in the non-flaring corona), (2) dynamics and magnetohydrodynamic
structures associated with magnetic reconnection processes ongoing in flares, and even (3) generation of
supra-thermal distributions of coronal plasmas associated with flares. Nevertheless, imaging-spectroscopic investigation
of the soft X-ray corona has so far remained unexplored due to difficulty in the instrumentation for achieving this aim.
With the advent of recent remarkable progress in CMOS-APS detector technology, the photon-counting X-ray telescope
will be capable of, in addition to conventional photon-integration type exposures, performing imaging-spectroscopic
investigation on active regions and flares, thus providing, for example, detailed temperature information (beyond the sofar-
utilized filter-ratio temperature) at each spatial point of the observing target. The photon-counting X-ray telescope
will emply a Wolter type I optics with a piece of a segmented mirror whose focal length 4 meters, combined with a
focal-plane CMOS-APS detector (0.4-0.5"/pixel) whose frame read-out rate required to be as high as 1000 fps.
The solar chromosphere is an important boundary, through which all of the plasma, magnetic fields and energy in the
corona and solar wind are supplied. Since the Zeeman splitting is typically smaller than the Doppler line broadening in
the chromosphere and transition region, it is not effective to explore weak magnetic fields. However, this is not the case
for the Hanle effect, when we have an instrument with high polarization sensitivity (~ 0.1%). "Chromospheric Lyman-
Alpha SpectroPolarimeter (CLASP)" is the sounding rocket experiment to detect linear polarization produced by the
Hanle effect in Lyman-alpha line (121.567 nm) and to make the first direct measurement of magnetic fields in the upper
chromosphere and lower transition region. To achieve the high sensitivity of ~ 0.1% within a rocket flight (5 minutes) in
Lyman-alpha line, which is easily absorbed by materials, we design the optical system mainly with reflections. The
CLASP consists of a classical Cassegrain telescope, a polarimeter and a spectrometer. The polarimeter consists of a
rotating 1/2-wave plate and two reflecting polarization analyzers. One of the analyzer also works as a polarization beam
splitter to give us two orthogonal linear polarizations simultaneously. The CLASP is planned to be launched in 2014
WISH is a new space science mission concept whose primary goal is to study the first galaxies in the early universe.
We will launch a 1.5m telescope equipped with 1000 arcmin2 wide-field NIR camera by late 2010's in order to conduct
unique ultra-deep and wide-area sky surveys at 1-5 micron. The primary science goal of WISH mission is pushing the
high-redshift frontier beyond the epoch of reionization by utilizing its unique imaging capability and the dedicated
survey strategy. We expect to detect ~10<sup>4</sup> galaxies at z=8-9, ~3-6x10<sup>3</sup> galaxies at z=11-12, and ~50-100 galaxies at
z=14-17 within about 5 years of the planned mission life time. It is worth mentioning that a large fraction of these
objects may be bright enough for the spectroscopic observations with the extremely large telescopes. By adopting the optimized strategy for the recurrent observations to reach the depth, we also use the surveys to detect transient objects.
Type Ia Supernova cosmology is thus another important primary goal of WISH. A unique optical layout has been
developed to achieve the diffraction-limited imaging at 1-5micron over the required large area. Cooling the mirror and
telescope to ~100K is needed to achieve the zodiacal light limited imaging and WISH will achieve the required
temperature by passive cooling in the stable thermal environment at the orbit near Sun-Earth L2. We are conducting the
conceptual studies and development for the important components of WISH including the exchange mechanism for the
wide-field filters as well as the primary mirror fixation.
We present scientific as well as engineering overview of the X-Ray Telescope (XRT) aboard the Japanese <i>Solar-B</i> mission to be launched in 2006, with emphasis on the focal plane CCD camera that employs a 2k x 2k back-thinned CCD. Characterization activities for the flight CCD camera made at the National Astronomical Observatory of Japan (NAOJ) are discussed in detail with some of the results presented.
Future large aperture telescope projects will require very lightweight mirrors that can be produced at significantly lower cost and faster production times than currently possible. Tailorable, low thermal expansion composite materials offer an attractive path to achieve these goals. Application of carbon/carbon composites is particularly attractive as these materials do not exhibit the moisture-absorption-related expansion problems observed in typical resin matrix composites. The National Astronomical Observatory of Japan and Mitsubishi Electric Corporation are collaborating to develop materials and surface finishing technologies to enable future carbon/carbon composite mirror applications. Material processing techniques for improved substrate surface finish have been developed. An innovative surface finish approach involving high precision machining of a metal layer applied to the mirror surface has also been developed. As a result, 150mm diameter C/C spherical mirror with honeycomb sandwich structure was successfully demonstrated.
The solar optical telescope onboard the Solar-B is aimed to perform a high precision polarization measurements of the solar spectral lines in visible wavelengths to obtain, for the first time, continuous sets of high spatial resolution (~0.2arcsec) and high accuracy vector-magnetic-field map of the sun for studying the mechanisms driving the fascinating activity phenomena occurring in the solar atmosphere. The optical telescope assembly (OTA) is a diffraction limited, aplanatic Gregorian telescope with an aperture of Φ500mm. With a collimating lens unit and an active folding mirror, the OTA provides a pointing-stabilized parallel beam to the focal plane package (FPP) with a field of view of about 360x200arcsec. In this paper we identify the key technical issues of OTA for achieving the mission goal and describe the basic concepts in its optical, mechanical and thermal designs. The strategy to verify the in-orbit performance of the telescope is also discussed.
Extremely stable pointing of the telescope is required for images on the CCD cameras to accurately measure the nature of magnetic field on the sun. An image stabilization system is installed to the Solar Optical Telescope onboard SOLAR-B, which stabilizes images on the focal plane CCD detectors in the frequency range lower than about 20Hz. The system consists of a correlation tracker and a piezo-based tip-tilt mirror with servo control electronics. The correlation tracker is a high speed CCD camera with a correlation algorithm on the flight computer, producing a pointing error from series of solar granule images. Servo control electronics drives three piezo actuators in the tip-tilt mirror. A unique function in the servo control electronics can put sine wave form signals in the servo loop, allowing us to diagnose the transfer function of the servo loop even on orbit. The image stabilization system has been jointly developed by collaboration of National Astronomical Observatory of Japan/Mitsubishi Electronic Corp. and Lockheed Martin Advanced Technology Center Solar and Astrophysics Laboratory. Flight model was fabricated in summer 2003, and we measured the system performance of the flight model on a laboratory environment in September 2003, confirming that the servo stability within 0-20 Hz bandwidth is 0.001-0.002 arcsec rms level on the sun.
We present the design and initial flight results of a balloon-borne hard X-ray detector system for observing high-resolution spectra of solar flares. The instrument is designed to achieve a 3 keV energy resolution over the energy range of 15-120 keV. The instrument uses sixteen 10×10×0.5mm cadmium telluride (CdTe) detectors with indium electrodes that act as Schottky barriers. Pre-flight tests confirmed that all detectors exceeded the target 3 keV resolution. The detector system is designed to optimize radiative cooling in order to achieve the operating temperature of 0°C without refrigeration mechanisms. The first flight took place on August 29, 2001 and while no major flares were observed, the instrument operation was verified and a detector temperature of -13° C was achieved. The second flight took place on May 24, 1974 and during the 8 hours of level flight at an altitude of 41km, we succeeded in observing a class M1.1 solar flare.
This paper describes the design and prelaunch performance of the tip-tilt mirror (TTM) system developed for the XUV Cassegrain telescope aboard the ISAS sounding rocket experiment. The spatial resolution of the telescope is about 5 arcsec, whereas the rocket pointing is only controlled to be within +/- 0.5 degree around the target without stability control. The TTM is utilized to stabilize the XUV image on the focal planes by tilting the secondary mirror with two-axes fixed-coil type actuators. The two position- sensitive detectors in the telescope optics and in the TTM mechanical structure from the normal and local closed-loop modes. The TTM has four grain modes with automatic transition among the modes. The low gain mode is used in the initial acquisition, and in case the TTM loses the tracking. The high gain mode is used in the normal tracking mode. This arrangement provides us with the wide initial acquisition angle with single TTM system as well as the high pointing accuracy once the tracking is established. The TTM has a launch-lock mechanism against the launch vibration of 16G. The closed-loop control with command and telemetry interface is done by the flight software against the launch vibration of 16G. The closed-loop control with command and telemetry interface is done by the flight software on the DSP processor. The use of the fast processor brings in the significant reduction in the weight and size of the control- electronics, more flexible control system, and shorter design and testing period.
We present the development status of the normal incidence XUV multilayer mirrors for XUV Doppler telescope, which observes coronal velocity fields of the whole sun. The telescope has two narrow band-pass multilayer mirrors tuned to slightly longer and shorter wavelengths around the Fe XIV line at 211.3 Angstrom. From the intensity difference of the images taken with these two bands, we can obtain Dopplergram of 1.8 MK plasma of the whole sun. It is required that the multilayer has high wavelength-resolution ((lambda) /(Delta) (lambda) approximately 30 per mirror), anti-reflection coating for intense He II 304 angstrom emission line and high d-spacing uniformity of approximately 1%.
We present an overview of a sounding-rocket experiment that is scheduled to be launched by the Institute of Space and Astronautical Science (ISAS) in January 1998, the rising phase of the 11-year activity cycle of the sun. The purpose of this experiment is (1) to obtain whole-sun images taken in an XUV emission line, Fe XIV 211 A, using the normal incidence multilayer optics with a high spectral resolution of about 40, and (2) to carry out the velocity-field measurement with a detection limit as high as 100 km/s.
We present an overview of an ongoing Japanese sounding rocket project with the Solar XUV Doppler telescope. The telescope employs a pair of normal incidence multilayer mirrors and a back-thinned CCD, and is designed to observe coronal velocity field of the whole sun by measuring line- of-sight Doppler shifts of the Fe XIV 211 angstroms line. The velocity detection limit is estimated to be better than 100 km/s. The telescope will be launched by the Institute of Space and Astronautical Science in 1998, when the solar activity is going to be increasing towards the cycle 23 activity maximum. Together with the overview of the telescope, the current status of the development of each telescope components including multilayer mirrors, telescope structure, image stabilization mechanism, and focal plane assembly, are reviewed. The observation sequence during the flight is also briefly described.
This paper reports on the newly developed graphite-cyanate composite pipes for high-precision space optics such as the Solar-B optical telescope. Fundamental mechanical, thermal, and hygroscopic properties of unidirectional graphite- cyanate laminates were evaluated, first. The orientation of fibers in the pipe was designed to minimize longitudinal thermal deformation. Model pipes were fabricated based on the design, and have conducted a series of measurements to evaluate the thermal expansion behavior, the hygroscopic performance, the thermal conductivity, and the long-term stability. Excellent performance of the pipe was successfully verified and the material was found to be the most promising candidate for space optics structures.