中川 貴雄

Using AKARI, the first Japanese satellite dedicated to infrared astronomy, we conducted multi-band large-area surveys around the ecliptic poles. The north ecliptic pole (NEP) is the best region for AKARI which has a sun-synchronous orbit that allows it conduct legacy surveys with all AKARI hands, i.e. nine bands in 2 - 24 mu m and 4 hands in 65 - 160 mu m. We prove that this survey, which has such unprecedented infrared wavelength coverage, is certainly unique and useful to search out new galaxy populations such as "PAH-luminous" galaxies.

We present the results of Spitzer Infrared Spectrograph low-resolution infrared 5-35 μm spectroscopy of nearby ultraluminous infrared galaxies (ULIRGs) at z < 0.15. We focus on the search for the signatures of buried active galactic nuclei (AGNs) in the complete sample of ULIRGs classified optically as non-Seyferts (LINERs or H II regions). In addition to polycyclic aromatic hydrocarbon (PAH) emission features at 6.2, 7.7, and 11.3 μm, the conventional tool of starburst-AGN separation, we use the optical depths of the 9.7 and 18 μm silicate dust absorption features to infer the geometry of energy sources and dust at the nuclei of these ULIRGs, namely, whether the energy sources are spatially well mixed with dust (a normal starburst) or are more centrally concentrated than the dust (a buried AGN). Infrared spectra of at least 30%, and possibly 50%, of the observed optical non-Seyfert ULIRGs are naturally explained by emission consisting of (1) energetically insignificant, modestly obscured (A < 20-30 mag) PAH-emitting normal starbursts and (2) energetically dominant, highly dust-obscured, centrally concentrated energy sources with no PAH emission. We interpret the latter component as a buried AGN. The fraction of ULIRGs showing some buried AGN signatures is higher in LINER ULIRGs than in H II region ULIRGs. Most of the luminous buried AGN candidates are found in ULIRGs with cool far-infrared colors. Where the absorption-corrected intrinsic AGN luminosities are derivable with little uncertainty, they are found to be of the order of 10 L , accounting for the bulk of the ULIRGs' luminosities. The 5-35 μm spectroscopic starburst/AGN classifications are generally consistent with our previous classifications based on 3-4 μm spectra for the same sample. © 2007. The American Astronomical Society. All rights reserved. V ⊙ 12

We present the results of high-precision measurements of the thermal expansion of sintered SiC, SiC-100, intended for use in cryogenic space telescopes, in which minimization of thermal deformation of the mirror is critical, and precise information of the thermal expansion is needed for the telescope design. The temperature range of the measurements extends from room temperature down to ∼10 K. Three samples, Nos. 1, 2, and 3, were manufactured from blocks of SiC produced in different lots. The thermal expansion of the samples was measured with a cryogenic dilatometer, consisting of a laser interferometer, a cryostat, and a mechanical cooler. The typical thermal expansion curve is presented using an eighth-order polynomial of the temperature. For the three samples, the coefficients of thermal expansion (CTE), ᾱ , ᾱ , and ᾱ , were derived for temperatures between 293 and 10 K. The average and the dispersion (1 σ rms) of these three CTEs are 0.816 × 10 and 0.002 × 10 K , respectively. No significant difference was detected in the CTE of the three samples from the different lots. Neither inhomogeneity nor anisotropy of the CTE was observed. Based on the CTE dispersion obtained, we performed a finite-element method (FEM) analysis of the thermal deformation of a 3.5 m diameter cryogenic mirror made of six SiC-100 segments. It was shown that the present CTE measurement has an accuracy that is sufficient for the design of the 3.5 m cryogenic infrared telescope mission SPICA (Space Infrared Telescope for Cosmology and Astrophysics). © 2007. The Astronomical Society of the Pacific. All rights reserved. 1 2 3 -6 -6 -1

We present the 3.5 m SPace Infrared telescope for Cosmology and Astrophysics (SPICA) space telescope, the launch of which is schedule around year 2015 by the Japanese HII-A rocket, and specifically discuss its use in the context of direct observation of extra-solar planets. This actively cooled (4.5 K), single aperture telescope will operate in the mid and far infrared spectral regions, and up to submillimetric wavelengths (200 μm). The lowest spectral region (5 to 20 μm), where the spatial resolution is the most favorable, will be dedicated to high contrast imaging with coronagraphy. This article describes the SPICA coronagraph project in terms of science, as well as our efforts to study a suitable instrumental concept, compatible with the constraints of the telescope architecture. To cite this article: L. Abe et al., C. R. Physique 8 (2007). © 2007 Académie des sciences.

Context. We present the results of the first laboratory experiment of checkerboard shaped pupil binary mask coronagraphs using visible light, in the context of the R&D activities for future mid-infrared space missions such as the 3.5 m SPICA telescope. Aims. The primary aim of this work is to demonstrate the coronagraphic performance of checkerboard masks down to a 10 peak-to-peak contrast, which is required to detect self-luminous extra-solar planets in the mid-infrared region. Methods. Two masks, consisting of aluminum films on a glass substrates, were manufactured using nano-fabrication techniques with electron beam lithography: one mask was optimized for a pupil with a 30% central obstruction and the other was for a pupil without obstruction. The theoretical contrast for both masks was 10 and no adaptive optics system was employed. Results. For both masks, the observed point spread functions were quite consistent with the theoretical ones. The average contrast measured within the dark regions was 2.7 × 10 and 1.1 × 10 . Conclusions. The coronagraphic performance significantly outperformed the 10 requirement and almost reached the theoretical limit determined by the mask designs. We discuss the potential application of checkerboard masks for mid-infrared coronagraphy, and conclude that binary masks are promising for future high-contrast space telescopes. © ESO 2006. -6 -7 -7 -6

We present the status of the development of a coronagraph for the Space Infrared telescope for Cosmology and Astrophysics (SPICA). SPICA is the next generation of infrared space-borne telescope missions following to AKARI, led by Japan. SPICA will carry a telescope that has a 3.5 m diameter monolithic primary mirror and the whole telescope will be cooled to 4.5 K. It is planned to launch SPICA into the sun-earth L2 libration halo orbit using H II-A rocket in the middle of the 2010s and execute infrared observations at wavelengths mainly between 5 and 200 micron. The SPICA mission gives us a unique opportunity for coronagraph observations, because of the large telescope aperture, the simple pupil shape, the capability of infrared observations from space, and the early launch. We have started development of the SPICA coronagraph in which the primary target is direct observation of extra-solar Jovian planets. The main wavelengths of observation, the required contrast and the inner working angle (IWA) of the SPICA coronagraph instrument are set to be 5-27 micron, 10 , and a few λ/D (and as small as possible), respectively, in which λ is the observation wavelength and D is the diameter of the telescope aperture (3.5m). We focused on a coronagraph with a binary shaped pupil mask as the primary candidate for SPICA because of its feasibility. Nano-fabrication technology using electron beam lithography was applied to manufacture a high precision mask and a laboratory experiment with a He-Ne laser (λ=632.8nm) was performed in air without active wavefront control. The raw contrast derived from the average measured in the dark region reached 6.7×10 . On the other hand, a study of Phase Induced Amplitude Apodization (PIAA) was started in an attempt to achieve higher performance, i.e., smaller IWA and higher throughput. A hybrid solution using PIAA and a shaped pupil mask was proposed. A laboratory experiment was performed using a He-Ne laser with active wavefront control via a 32 × 32 channel deformable mirror. A raw contrast of 6.5 × 10 was achieved. Designs of binary shaped pupil mask are presented for the actual SPICA pupil which is obstructed by the telescope's secondary mirror and its support. Subtraction of point spread function (PSF) was also evaluated. -6 -8 -7

Reported in this paper is the initial phase operation of the attitude and orbit control system (AOCS) of Japanese satellite "AKARI". AKARI is the first Japanese satellite dedicated to the infrared astronomy. AKARI was successfully launched by M-V rocket from Kagoshima Space Center on February 22, 2006. Just after the launch, AKARI faced to a serious problem. It was found that something interferes with the fields of view of two (out of two) sun sensors. The two sensors were out of use in the subsequent AOCS operation. Fortunately, by using two star trackers and gyros, the attitude accuracy required for the scientific observation can be achieved without the sun sensors. However, as other many satellites, the sun sensors were to play important roles in AKARI's AOCS operation. Firstly, they were to be used for sun acquisition at the very initial phase. The anomaly prevented us from carrying out the pre-planned sequence. However, the crisis was overcome with the appropriate ground support operation. Secondly, for the observation in far infrared wavelength, the telescope and the scientific instruments of AKARI are stored in the cryostat and cooled by liquid Helium. To prevent the sun light inflow to the telescope, the attitude of AKARI against the sun is strictly constrained after the scientific observation starts. The sun sensors were to be used to watch the sun direction to keep the appropriate attitude against the sun even when AKARI falls into the safe mode. To save the cryostat from the sun light in the absence of the sun sensors, AOCS architecture was reconfigured so that the equivalent function is achieved by the remaining sensors. The experiences in this recovery operation are mainly reported in this paper. In addition, unexpected continuous orbit rising was observed in the operation. The cause of the phenomenon and the investigation process are also reported.

We present a five-band (u*, g′, r′, i′, z′) optical photometry catalog of the sources in the north ecliptic pole (NEP) region based on deep observations made with MegaCam at CFHT. The source catalog covers about 2 square degree area centered at the NEP and reaches depths of about 26 mag for u*, g′, r′ bands, about 25 mag for r′ band, and about 24 mag for z′ band (4 σ detection over a 1″ aperture). The total number of cataloged sources brighter than r′ = 23 mag is about 56,000 including both point sources and extended sources. From the investigation of photometric properties using the color-magnitude diagrams and color-color diagrams, we have found that the colors of extended sources are mostly (u* - r′) < 3.0 and (g′ - z′) > 0.5. This can be used to separate the extended sources from the point sources reliably, even for the faint source domain where typical morphological classification schemes hardly work efficiently. We have derived an empirical color-redshift relation of the red sequence galaxies using the Sloan Digital Sky Survey data. By applying this relation to our photometry catalog and searching for any spatial overdensities, we have found two galaxy clusters and one nearby galaxy group. © 2007. The American Astronomical Society. All rights reserved.

We present the observations of the reflection nebulae IC 4954 and IC 4955 region with the Infrared Camera and the Far-Infrared Surveyor (FIS) on board the infrared astronomical satellite AKARI during its performance verification phase. We obtained 7 band images from 7 to 160μm with higher spatial resolution and higher sensitivities than previous observations. The spatial variation in the mid-infrared color suggests that the star-formation in IC 4954/4955 is progressing from south-west to north-east. The FIS 4-band data from 65 μm to 160/z m allow us to correctly estimate the total infrared luminosity from the region, which is about one sixth of the energy emitted from the existing stellar sources. Five candidates for young stellar objects have been detected as point sources for the first time in the 11 μm image and it is suggested that that current star-formation has been triggered by previous star-formation activities. A wide area map of the size of about Io around the IC 4954/4955 region was created from the AKARI mid-infrared All-Sky Survey data. Together with the H 121 cm data, it suggests a large hollow structure of a degree scale, on whose edge the IC 4954/4955 region has been created, indicating star formation over three generations in largely different spatial scales. © 2007. Astronomical Society of Japan.

The Cosmic Far-Infrared Background (CFIRB) contains information about the number and distribution of contributing sources and thus gives us an important key to understand the evolution of galaxies. Using a confusion study to set a fundamental limit to the observations, we investigate the potential to explore the CFIRB with AKARI/FIS deep observations. The Far-Infrared Surveyor (FIS) is one of the focal-plane instruments on the AKARI (formerly known as ASTRO-F) satellite, which was launched in early 2006. Based upon source distribution models assuming three different cosmological evolutionary scenarios (no evolution, weak evolution, and strong evolution), an extensive model for diffuse emission from infrared cirrus, and instrumental noise estimates, we present a comprehensive analysis for the determination of the confusion levels for deep far-infrared observations. We use our derived sensitivities to suggest the best observational strategy for the AKARI/FIS mission to detect the CFIRB fluctuations. If the source distribution follows the evolutionary models, observations will be mostly limited by source confusion. We find that we will be able to detect the CFIRB fluctuations and that these will in turn provide information to discriminate between the evolutionary scenarios of galaxies in most low-to-medium cirrus regions. © 2007 COSPAR.

SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is a Japanese astronomical infrared satellite project with a 3.5-m telescope. The target year for launch is 2017. The telescope is cooled down to 4.5 K in space by a combination of newly-developed mechanical coolers with an efficient radiative cooling system at the L2 point. The SPICA telescope has requirements for its total weight to be lighter than 700 kg and for the imaging performance to be diffraction-limited at 5 μm at 4.5 K. Material for the SPICA telescope mirrors is silicon carbide (SiC). Among various types of SiC, primary candidates comprise normally-sintered SiC, reaction-sintered SiC, and carbon-fiber- reinforced SiC; the latter two have been being developed in Japan. This paper reports the current design and status of the SPICA telescope along with our recent activities on the cryogenic optical testing of SiC and C/SiC composite mirrors, including the development of an innovative support mechanism for cryogenic mirrors, which are based on lessons learned from a SiC 70 cm telescope onboard the previous Japanese infrared astronomical mission AKARI.

Far-infrared (IR) images of the nearby Sb galaxy NGC 2841 and the Sc galaxy NGC 2976 at wavelengths of 65, 90, 140, and 160 μm have been obtained with the Far-Infrared Surveyor (FIS) onboard AKARI. Both galaxies reveal similar morphologies of dust rings. They are, however, significantly different in the dust temperature: a cold (∼ 21 K) ring for NGC 2841 and a warm (∼ 30 K) ring for NGC 2976, which presumably reflects the difference in the origin of the ring structure for the different Hubble types of the galaxy. In addition to the dust-ring structure, a warm dust component was detected from the central region of NGC 2841, which may be attributed to heating by its Low-Ionization Nuclear Emission-line Region nucleus. As for NGC 2976, an extended dust component was observed along the minor axis, which shows a distribution somewhat asymmetrical to the galactic disk; this might be associated with the H I bridge in the M 81/M 82 group that NGC 2976 belongs to. By taking advantage of a wealth of the far-IR bands of the FIS, it has been demonstrated that the spectral energy distribution of NGC 2841 is spatially more variable than that of NGC 2976. © 2007. Astronomical Society of Japan.

The Far-Infrared Surveyor (FIS) is one of two focal-plane instruments on the AKARI satellite. FIS has four photometric bands at 65, 90, 140, and 160 μm, and uses two kinds of array detectors. The FTS arrays and optics are designed to sweep the sky with high spatial resolution and redundancy. The actual scan width is more than eight arcminutes, and the pixel pitch matches the diffraction limit of the telescope. Derived point-spread functions (PSFs) from observations of asteroids are similar to those given by the optical model. Significant excesses, however, are clearly seen around tails of the PSFs, whose contributions are about 30% of the total power. All FIS functions are operating well in orbit, and the performance meets the laboratory characterizations, except for the two longer wavelength bands, which are not performing as well as characterized. Furthermore, the FIS has a spectroscopic capability using a Fourier transform spectrometer (FTS). Because the FTS takes advantage of the optics and detectors of the photometer, it can simultaneously make a spectral map. This paper summarizes the in-flight technical and operational performance of the FIS. © 2007. Astronomical Society of Japan.

Reported in this paper is the initial phase operation of the attitude and orbit control system (AOCS) of Japanese satellite "AKARI". AKARI is the first Japanese satellite dedicated to the infrared astronomy. AKARI was successfully launched by M-V rocket from Kagoshima Space Center on February 22, 2006. Just after the launch, AKARI faced to a serious problem. It was found that something interferes with the fields of view of two (out of two) sun sensors. The two sensors were out of use in the subsequent AOCS operation. Fortunately, by using two star trackers and gyros, the attitude accuracy required for the scientific observation can be achieved without the sun sensors. However, as other many satellites, the sun sensors were to play important roles in AKARI's AOCS operation. Firstly, they were to be used for sun acquisition at the very initial phase. The anomaly prevented us from carrying out the pre-planned sequence. However, the crisis was overcome with the appropriate ground support operation. Secondly, for the observation in far infrared wavelength, the telescope. and the scientific instruments of AKARI are stored in the cryostat and cooled by liquid Helium. To prevent the sun light inflow to the telescope, the attitude of AKARI against the sun is strictly constrained after the scientific observation starts. The sun sensors were to be used to watch the sun direction to keep the appropriate attitude against the sun even when AKARI falls into the safe mode. To save the cryostat from the sun light in the absence of the sun sensors, AOCS architecture was reconfigured so that the equivalent function is achieved by the remaining sensors. The experiences in this recovery operation are mainly reported in this paper. In addition, unexpected continuous orbit rising was observed in the operation. The cause of the phenomenon and the investigation process are also reported.

We present the properties of 11 μm selected sources detected in the early data of the North Ecliptic Pole Deep (NEP-Deep) Survey of AKARI. The data set covers 6 wavelength bands from 2.5 to 11 μm, with exposure times of 10-20 minutes. This field lies within the CFHT survey with four filter bands (g′, r′, i′, z′), enabling us to establish nearly continuous spectral energy distributions (SEDs) for wavelengths ranging from 0.4 to 11 μm. The main sample studied here consists of 72 sources whose 11 μm AB magnitudes are equal to or brighter than 18.5 (144 μJy), which is complete to more than 90%. The 11 μm band has an advantage of sampling star-forming galaxies with low-to-medium redshifts, since the prominent PAH feature shifts into this band. As expected, we find that the majority (71%) of 11 μm bright sources are star-forming galaxies at 0.2 ≲ z ≲ 0.7 with L ∼ 10 -10 L based on detailed modelling of the SEDs. We also find four AGNs lying at various redshifts in the main sample. In addition, we discuss a few sources that have non-typical SEDs of the main sample, including a brown-dwarf candidate, a steep power-law source, a flat-spectrum object, and an early-type galaxy at moderate redshift. © 2007. Astronomical Society of Japan. IR ⊙ 10 12

We present the results of optical identifications for 257 mid-infrared sources detected with a deep 15 μm survey over approximately 80 arcmin area in the AKARI performance verification field near the North Ecliptic Pole. The 15 μm fluxes of the sources range from 1 mJy down to 40 μJy, approximately one half of which are below 100 μJy. Optical counterparts were searched for within a 2″-3″ radius in both the BVRi′z′ catalog generated by using the deep Subaru/Suprime-cam field, which covers one-third of the performance verification field, and the g′r′i′z′ catalog based on observations made with MegaCam at CFHT. We found that the B -R and R-z′ colors of sources with successful optical identifications are systematically redder than that of the entire optical sample in the same field. Moreover, approximately 40% of the 15 μm sources show colors with R-L15 > 5, which cannot be explained by the spectral energy distribution (SED) of normal quiescent spiral galaxies, but are consistent with SEDs of redshifted (z > 1) starburst or ultraluminous infrared galaxies. This result indicates that the fraction of the ultraluminous infrared galaxies in our faint 15 μm sample is much larger than that in our brighter 15 μm sources, which is consistent with the evolving mid-infrared luminosity function derived by recent studies based on Spitzer 24 μm deep surveys. Based on an SED fitting technique, the nature of the faint 15 μm sources is further discussed for a selected number of sources with available K -band data. © 2007. Astronomical Society of Japan. 2 8

AKARI, the first Japanese satellite dedicated to infrared astronomy, was launched on 2006 February 21, and started observations in May of the same year. AKARI has a 68.5 cm cooled telescope, together with two focal-plane instruments, which survey the sky in six wavelength bands from mid- to far-infrared. The instruments also have a capability for imaging and spectroscopy in the wavelength range 2-180 μm in the pointed observation mode, occasionally inserted into a continuous survey operation. The in-orbit cryogen lifetime is expected to be one and a half years. The All-Sky Survey will cover more than 90% of the whole sky with a higher spatial resolution and a wider wavelength coverage than that of the previous IRAS all-sky survey. Point-source catalogues of the All-Sky Survey will be released to the astronomical community. Pointed observations will be used for deep surveys of selected sky areas and systematic observations of important astronomical targets. These will become an additional future heritage of this mission. © 2007. Astronomical Society of Japan.

We present an overview and the current status of SPICA (Space Infrared Telescope for Cosmology and Astrophysics), which is an astronomical mission with a cryogenically cooled 3.5 m telescope optimized for mid- and far-infrared astronomy. Because of its high spatial resolution and unprecedented sensitivity in the mid- to far-infrared, SPICA can address a number of key problems in current astrophysics, ranging from the star-formation history of the universe to the formation of planets. To reduce the mass of the whole mission, SPICA carries no cryogen. SPICA will be launched at ambient temperature and cooled down on orbit by mechanical coolers on board with an efficient radiative cooling system. This combination enables a 3.5-m class cooled (4.5 K) telescope in space. We also describe recent activities of the technology development programs for SPICA. The target year of the launch of SPICA is mid 2010s. © 2007.

We investigate the segregation of the extragalactic population via colour criteria to produce an efficient and inexpensive methodology to select specific source populations as a function of far-infrared flux. Combining galaxy evolution scenarios and a detailed spectral library of galaxies, we produce simulated catalogues incorporating segregation of the extragalactic population into component types (normal, star-forming, AGN) via colour cuts. As a practical application we apply our criteria to the deepest survey to be undertaken in the far-infrared with the AKARI (formerly ASTRO-F) satellite. Using the far-infrared wavebands of the Far-Infrared Surveyor (FIS, one of the focal-plane instruments on AKARI) we successfully segregate the normal, starburst and ULIRG populations. We also show that with additional MIR imaging from AKARI's Infrared Camera (IRC), significant contamination and/or degeneracy can be further decreased and show a particular example of the separation of cool normal galaxies and cold ULIRG sources. We conclude that our criteria provide an efficient means of selecting source populations (including rare luminous objects) and produce colour-segregated source counts without the requirement of time intensive ground-based follow up to differentiate between the general galaxy population. © 2007 COSPAR.

We present results on mid-infrared imaging and spectroscopic observations of the nearby late-type spiral NGC 6946 with the Infrared Camera on board AKARI. Based on mid-infrared imaging with the S7 (7 μm) and S11(11 μm) bands, we found that the S7/S11 ratios have larger values in the arm region, containing many star-forming regions, than in the interarm. Slit spectra of an interarm and a star-forming region show a series of unidentified infrared (UIR) bands at 6.2, 7.7, 8.6, and 11.2 μm. The strengths of the 6.2, 7.7, and 8.6 μm bands are larger relative to the 11.2 μm band in the star-forming region, than in the interarm, even if the interstellar extinction of A = 3 mag towards the star-forming region is taken into account. The increase in the 6.2 μm and 7.7 μm features relative to the 11.2 μm feature is consistent with the ionization model of PAHs. The ratio of the UIR features to the plateau emission under the 7.7 μm and 8.6 μm features and/or the ratio of the 7.6 μm/7.8 μm components in the 7.7 μm feature increase in the star-forming region compared to the interarm. This variation can be accounted for by the hypothesis that the photo-evaporation of PAH clusters produce small free-flying PAHs in the star-forming region. The ratios of 6.2 μm/11.2 μm, 7.7 μm/11.2 μm, and 8.6 μm/11.2 μm may be tools to measure the star-formation activity in remote galaxies if these ratios and their variations are well examined and established for a large sample. © 2007. Astronomical Society of Japan. V

We present a new physical insight into molecular tori around AGNs, based on the results of infrared spectroscopy of gaseous CO ro-vibrational absorption lines.

The nearby face-on spiral galaxy M 101 has been observed with the Far-Infrared Surveyor onboard AKARI. The far-infrared four-band images reveal fine spatial structures of M 101, which include global spiral patterns, giant H II regions embedded in outer spiral arms, and a bar-like feature crossing the center. The spectral energy distribution of the whole galaxy shows the presence of a cold dust component (18 K) in addition to a warm dust component (55 K). The distribution of the cold dust is mostly concentrated near the center, and appears to be smoothly distributed over the entire extent of the galaxy, whereas the distribution of warm dust indicates some correlation with the spiral arms, and has spotty structures, such as four distinctive bright spots in the outer disk in addition to a bar-like feature near the center, tracing the CO intensity map. The star-formation activity of the giant H II regions that spatially correspond to the former bright spots is found to be significantly higher than that of the rest of the galaxy. The latter warm dust distribution implies that there are significant star-formation activities in the entire bar filled with molecular clouds. Unlike our Galaxy, M 101 is a peculiar normal galaxy with extraordinary active star-forming regions. © 2007. Astronomical Society of Japan. -10 -25 +4 +9

We present an initial analysis of AKARI 18 μm-selected galaxies using all 9 photometric bands at 2-24 μm available in the Infrared Camera (IRC), in order to demonstrate new capabilities of AKARI cosmological surveys with this unprecedented wavelength coverage at mid-infrared (MIR) bands. We detected 72 sources at 18 μm in an area of 50.2 arcmin in the AKARI/IRC monitor field towards the North Ecliptic Pole (NEP). From this sample, 25 galaxies with probable redshifts of z ≳; 0.5 were selected with a single colour cut (N2-N3 ≳; 0.1) for a detailed spectral energy distribution (SED) analysis with ground-based BVRi′z′JK data. Using an SED radiative transfer model of starbursts covering the wavelength range UV-submm, we derived photometric redshifts from the optical-MIR SEDs of 18 μm-selected galaxies. From the best-fit SED models, we showed that the IRC all-band photometry is capable of tracing a steep rise in the flux at the blue side of the polycyclic aromatic hydrocarbon (PAH) 6.2 μm emission feature. This indicates that the IRC all-band photometry is useful to constrain the redshift of infrared galaxies, specifically for dusty galaxies with a less prominent 4000 Å;break. Also, we found that the flux dip between the PAH 7.7 and 11.2 μm emission feature is recognizable in the observed SEDs of galaxies at z ∼ 1. This pilot study suggests the possibility of detecting many interesting galaxy properties in the NEP-Deep and Wide surveys, such as a systematic difference in SEDs between high- and low-z Ultra-Luminous InfraRed Galaxies, and a large variation of the PAH inter-band strength ratio in galaxies at high redshifts. © 2007. Astronomical Society of Japan. 2

The formation and growth of supermassive black holes (SMBHs) physically linked with bulges are considered. We focus on the radiation hydrodynamic process for the growth of SMBH in the optically thick starburst phase, where radiation from bulge stars drives the mass accretion on to a galactic center through radiation drag effect. In the present scenario, the AGN luminosity-dominant phase (QSO phase) is preceded by the host luminosity-dominant phase, which is called "proto-QSO phase". Comparing with observations, we found that the ultraluminous infrared galaxies that contain a type I Seyfert nucleus (a type I ULIRG) are the early phase of BH growth, namely correspond to the proto-QSO phase. © 2006 Elsevier B.V. All rights reserved.

The AKARI (formerly known as ASTRO-F) mission is the first Japanese satellite dedicated for large area surveys in the infrared (Murakami et al. 2004). AKARI was launched successfully on February 22nd 2006 (JST) from JAXA's Uchinoura Space Centre, Japan. AKARI is now orbiting around the Earth in a Sun-synchronous polar orbit at the altitude of 700 km. The 68.5 cm aperture telescope and scientific instruments are cooled to 6K by liquid Helium and mechanical coolers. The expected liquid Helium holding time is now found to be at least one year after the successful aperture lid-opening on 2006 April 13th (JST). AKARI will perform the most advanced all-sky survey in 6 mid- to far-infrared wavebands since the preceding IRAS mission over 2 decades ago. Deep imaging and spectroscopic surveys near the ecliptic poles with pointed observations are also on-going in 13 wavelength bands at 2-160 m (see Table 1, details are given in Matsuhara et al. 2006). AKARI is a perfect complement to Spitzer in respect of its wide sky area and wavelength coverage. Two unique aspects of the pointing deep surveys with AKARI are: many imaging bands including the wavelength gap of Spitzer (8-24 m), and the slitless spectroscopic capability (Ohyama et al. in this proceeding). Not only the All-Sky Survey but also the deep pointing surveys near the ecliptic poles over ∼15 deg in total will be particularly well suited to construct the luminosity functions of the infrared galaxies, to evaluate their clustering nature, and also to discover rare, exotic objects at various redshifts out to z ∼ 3. AKARI is also capable of detecting and measuring the spectrum and the fluctuations of the cosmic infrared background. The in-orbit sensitivity and spatial resolution of the surveys are found to be sufficient to achive the scientific goals listed above. © 2007 International Astronomical Union. 2

Ge:Ga photoconductive devices are the most sensitive detectors for far-infrared (FIR) satellite instruments; a combination of stressed and unstressed detectors continuously covers the wide wavelength range of 40-200 μm. However, the performance of these detectors is known to be severely influenced by the ionizing radiation environment in space. In order to investigate global properties of low-dose radiation effects, γ-ray irradiation of the Ge:Ga (stressed and unstressed) detectors was performed by using radioactive sources Co and Cs under various levels of FIR photon conditions. Substantial enhancement in detector responsivity was observed during the irradiation for both types of detectors. After cessation of the irradiation, significant systematic differences were found between the stressed and unstressed detectors in the relaxation rate of the enhanced responsivity and effectiveness of curing procedures. It is concluded that the former is attributed to the difference in the averaged energy of the FIR photons falling on the detector, while the latter is due to the difference in the Ga ionization energy for the stressed and unstressed Ge:Ga. © 2005 Elsevier B.V. All rights reserved. 60 137

This paper reports the 4 K- and 1 K-class mechanical coolers developed for space use. The 4 K-class cooler has been developed for Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES), which is to be operated onboard the International Space Station (ISS). The cooling capacity is 20 mW at 4.5 K, with the total input power of approximately 120 W. The 1 K-class cooler has been developed for cooling far-infrared detectors to 1.7 K in the Space Infrared Telescope for Cosmology and Astrophysics (SPICA). The cooling capacity is 10 mW at 1.7 K and the total input power to the cooler is about 180 W. A future possible cryogen-free cooling system for temperature below 0.1 K is also presented, which uses these coolers as a pre-cooler. © 2006 Elsevier B.V. All rights reserved.

Since the next cryogenic infrared mission "JAXA/SPICA" employs advanced mechanical cryocoolers with effective radiant cooling in place of cryogen, the primary mirror, 3.5 m in diameter, and the optical bench can be maintained at 4.5 K for at least 5 years. First, the feasibility of the thermal design of the cryogenic system is presented. A 20 K-class Stirling cryocooler was then improved in cooling capacity and reliability for the mission, and the effects of contaminated working gas or new regenerator materials on cooling performance were investigated. Development of a new He-JT (Joule-Thomson) cryocooler for use at 1.7 K is also described, along with the successful results of a cooling capacity higher than the required 10 mW. A 4 K-class cryocooler was modified and developed for higher reliability over a five-year operational life and a higher cooling capacity exceeding the current 30 mW. Finally, we discuss a system for heat rejection from cryocoolers using thermal control devices. © 2005 Elsevier Ltd. All rights reserved. 3

We present concepts for the background-limited infrared-submillimeter spectrograph (BLISS) for the Japanese SPICA mission to launch early next decade. SPICA will be a 3.5-meter telescope cooled to below 5 K, and offers the potential for far-IR observations limited only by the zodiacal dust emission. BLISS will provide moderate-resolution (R 1000) spectroscopy at this background limit throughout the 40-600 μm band. With sensitivities below 10 Wm in modest integrations, BLISS-SPICA will enable the first survey spectroscopy of the redshift 0.5 to 5 galaxies which produce the far-IR background. Both WaFIRS waveguide grating spectrometers, and new compact cross-dispersed echelle grating designs are under consideration. Detectors must have sensitivities around 3 × 10 W / √Hz and have good efficiency. The most promising near-term approaches to cover the full band are transition-edge bolometers cooled to ∼50 mK with an adiabatic demagnetization refrigerator. -20 2 -20

We present the status of the development of a coronagraph for the Space Infrared telescope for Cosmology and Astrophysics (SPICA). SPICA is the next generation infrared space-borne telescope missions led by Japan. The SPICA satellite will be equipped with a telescope that has a 3.5 m diameter monolithic primary mirror and the whole telescope will be cooled to 4.5 K. The satellite is planed be launched early in the 2010s into the sun-earth L2 libration halo orbit and execute infrared observations at wavelengths mainly between 5 and 200 micron. The SPICA mission gives us a unique opportunity for coronagraph observations, because of the large telescope aperture, a simple pupil shape, capability of infrared observations from space and the early launch. We have started development of the SPICA coronagraph in which the primary target is direct observation of extra-solar Jovian planets. The main wavelengths of observation, the required contrast and the inner working angle (IWA) of the SPICA coronagraph instrument are set to be 5-20 micron, 106, and approximately 5 λ/D respectively, where λ is the observation wavelength and D is the diameter of the telescope aperture. Coronagraphs using a checkerboard mask and a concentric ring mask have been investigated. We found some solutions for the SPICA pupil, which has a large obstruction due to the secondary mirror and its supports. We carried out laboratory experiments to examine coronagraphs obtained using checkerboard-type pupil masks with a central obstruction. Nano-fabrication technology with electron beam was applied to manufacture a high precision mask consisting of a patterned aluminum film on a glass substrate and its performance was confirmed by experiments with visible light. Contrast higher than 106 was achieved. In the future, we will be developing a cryogenic mid-infrared test-bed to investigate the SPICA coronagraphs.

The design for robotic telescopes to observe Gamma-Ray Burst (GRB) afterglows and the results of observations are presented. Quickly fading bright GRB flashes and afterglows provide a good tool to study an extremely early universe. However, most large ground-based telescopes cannot afford to follow-up the afterglows and flashes quickly within a few hours since a GRB explosion. We re-modeled the existing middle-class 1.3 m 0 telescope of the near infrared band at ISAS in Japan to match for the above requirement. We also set a small telescope of 30 cm diameter with a conventional CCD. These telescopes can monitor afterglows quickly within a few minutes in J, H, Ks and R band with a grism spectrometer.

We present sets of configurations of binary-shaped pupil coronagraphs optimized for a realistic space telescope to directly detect extrasolar giant planets. For the purpose of mid-infrared observations, the target contrast ratio is set to 10 . We made a systematic assessment of the performance of two recently proposed pupil shapes, "checkerboard" and "concentric ring" masks, where a large central obstruction due to a secondary mirror and its related support spiders was introduced into the telescope pupil. It turned out that, if the secondary mirror diameter is smaller than ∼ 15% of the diameter of the primary, the checkerboard-type masks are more promising in terms of the total highcontrast area. With such a small secondary, we propose to modify the original symmetrical checkerboard apodization function. This modification enables us to achieve a 10 contrast at an inner working angle (IWA) of 4.0λ/D. On the other hand, when the secondary mirror size cannot be reduced to that level, the concentric ring masks are preferable because of their larger transmission. It was also found that the transmission through the optimal binary masks exhibits two characteristic features as the IWA increases: firstly, abrupt increases and secondly, plateaus. We attribute this nature of the binary apodization functions to the existence of threshold IWAs that allow large openings in the pupil. © 2006. Astronomical Society of Japan. -7 -7

The lightweight cryogenic telescope on board the Japanese infrared astronomical satellite, ASTRO-F, which is scheduled to be launched early in 2006, forms an F/6 Ritchey-Chretien system with a primary mirror of 710 mm in diameter. The mirrors of the ASTRO-F telescope are made of sandwich-type silicon carbide (SiC) material, comprising a porous core and a chemical-vapor-deposited coat of SiC on the surface. To estimate the optical performance of the flight model telescope, the telescope assembly was tested at cryogenic temperatures, the total wavefront errors of which were measured by an interferometer from outside a liquid-helium chamber. As a result, the wavefront error obtained at 9 K shows that the imaging performance of the ASTRO-F telescope is diffraction limited at a wavelength of 6.2 μm, which is a little worse than our original goal of diffraction-limited performance at 5.0 μm. © 2005 Optical Society of America.

SPICA is a cooled, single large-mirror space-telescope, which is under discussion as an succsesor of the ASTRO-F mission. One of the most ambitious challenges of the SPICA mission is the direct observations of exoplanets with a coronagraph instrument. We report cryogenic infrared optics to realize high quality wavefronts for the SPICA coronagraph. The SPICA satellite will be launched by an H-IIA rocket to Sun-Earth L2 Halo orbit early in the 2010s. The SPICA telescope is a Ritchey-Chretien optics with 3.5m diameter primary mirror, and cooled down to 4.5 K in orbit by radiation cooling and mechanical cryo-coolers. Main working wavelengths are 5-200 micron. Advantages of the SPICA coronagraph are the infrared wavelenths where the contrast between planets and central stars are smaller than the optical wavelengths, and that the cooled space telescope consists of monolithic mirrors. Development of light-weight cooled telescope is one of the most important tasks to realize SPICA. At the present, sintered SiC and carbon fiber reinforced SiC (C/SiC) composite are candidate materials for the mirrors, truss, and optical bench. For these materials, estimations and improvements of basic property and surface roughness in cryogenic temperatures have been carried out. Deformation of trial product mirrors by cooling is also examined. We are developing cryogenic deformable mirrors (DMs) because wave front accuracy of the SPICA telescope is 0.35 micron RMS, which is not enough for our coronagraphic instrument. For MEMS (Micro Electro Mechanical System) DM and some others, measurements of thermal deformation by cooling, electrical response, and heat generation are undergoing. Developments of a tip-tilt system for cryogenic usage started to cancel vibration caused by the cryo-coolers and other components and to realize a diffraction limit resolution. The first result of our binary mask coronagraph experiment is also shown. © 2006 International Astronomical Union.

As of early ∼2010's, the Japanese SPace Infrared telescope for Cosmology and Astrophysics (SPICA) space observatory will be launched. This actively cooled, cryogenic (4.5K), 3.5m telescope will operate in the mid and far infrared spectral regions. With its very high sensitivity, one of SPICA's aims will be the direct detection and characterization of extra-solar outer planets of nearby stars. The goal contrast ranges from 10 to 10 up to an angular separation of ∼5 arcsec. The relatively low angular resolution at MIR (5 to 20 μm) requires an efficient and robust coronagraphic mode working at cryogenic temperatures. In this presentation we describe several envisaged preliminary designs and assess their performance against the science goals and host telescope specifications. These are compared against numerical simulations and instrumental environment considerations, such as the need for an actively corrected wavefront. © 2006 International Astronomical Union. 5 6

We present configurations of shaped pupil coronagraphs optimized for a realistic telescope to directly detect extrasolar giant planets in the mid-IR wavelengths. This study is linked to the development of the coronagraphic instrument aboard SPICA (SPace Infrared telescope for Cosmology and Astrophysics). We made a systematic assessment of the performance of the "checkerboard" and "concentric ring" masks, introducing a large central obstruction (C.O.) due to a secondary mirror and its related support spiders. With a small secondary mirror, we also propose a modification to the original symmetrical checkerboard apodization, which enables us to achieve a 10 contrast level at 4.0 λ/D. The transmission through the optimal binary masks exhibits abrupt increases and plateaus as the inner working angle (IWA) is increased. We attribute these properties of binary apodization function to the existence of threshold IWAs that allow large openings in the pupil. © 2006 International Astronomical Union. -7

High spatial resolution observations of the CO(1-0), HCN(1-0), HCO (1-0), and CO(1-0) molecular lines toward the luminous infrared merger NGC 6240 have been performed using the Nobeyama Millimeter Array and the RAINBOW Interferometer. All of the observed molecular emission lines are concentrated in the region between the double nuclei of the galaxy. However, the distributions of both HCN and HCO emissions are more compact compared with that of CO, and they are not coincident with the star-forming regions. The HCN/ CO line intensity ratio is 0.25; this suggests that most of the molecular gas between the double nuclei is dense. A comparison of the observed high HCN/ CO intensity ratio, 5.9, with large velocity gradient calculations suggests that the molecular gas is dense [n(H ) = 10 cm ] and warm (T > 50K). The observed structure in NGC 6240 may be explained by time evolution of the molecular gas and star formation, which was induced by an almost head-on collision or very close encounter of the two galactic nuclei accompanied with the dense gas and star-forming regions. © 2005. Astronomical Society of Japan. 12 + 13 + 12 12 4-6 -3 2 kin

C/SiC composites are being evaluated for the fabrication of large-scale reflectors for Space Infrared Telescope for Cosmology and Astrophysics (SPICA), which is under development in Japan. The superior mechanical and thermo-mechanical properties of C/SiC composite makes it possible to fabricate a large-scaled optical mirror. These composites possess the advantages of low density, high stiffness, high bending strength, and low coefficient of thermal expansion and provide flexibility in structural design. During the C/SiC composite fabrication, carbon fiber and binder are mixed uniformely, and loaded into a metal mold and pressurized. The specific gravity of the C/SiC composites is 25% higher than other SiC composites and have the Young's modulus of 320 MPa. Preventing reaction of the carbon fibers with the silicon carbide matrix contributes to the improvement of fracture toughness. Pitch-based fibers were introduced as reinforcements in these composites to improve materials properties for the SPICA mirror.

The Space Infrared Telescope for Cosmology and Astrophysics (SPICA) mission is a Japanese astronomical infrared satellite project optimized for mid- to far-infrared observations. It will be launched at ambient temperature and cooled down on orbit by mechanical coolers on board with an efficient radiative cooling system, a combination of which allows us to have a 3.5-m class cooled (4.5 K) telescope in space. SPICA will give us deep insights into a number of key problems in present-day astronomy, ranging from the star-formation history of the universe to the formation of planets, owing to its high spatial resolution and unprecedented sensitivity in the mid- to far-infrared. We have made successful progress in the development of mechanical coolers, whereas silicon carbide and carbon-fiber reinforced silicon carbide have been extensively investigated as primary candidates for the SPICA telescope mirrors. We present the current status of the SPICA project as well as the results of technology developments. © 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

In this paper, we describe our recent activities on wave-front measurement of space infrared telescopes. Optical performance of the 685-mm lightweight telescope on board the Japanese infrared astronomical satellite, ASTRO-F, has been evaluated at cryogenic temperatures. The mirrors of the ASTRO-F telescope are made of sandwich-type silicon carbide (SiC) material, comprising porous core and CVD coat of SiC on the surface. The total wavefront errors of the telescope were measured with an interferometer from outside a liquid-helium chamber; a 75-cm reflecting flat mirror was used for auto-collimating the light from the interferometer. The cryogenic deformation of the flat mirror was derived independently by shifting it in the chamber and its contribution to the wavefront error was removed. In addition to the ASTRO-F telescope, we are currently developing a 3.5-m telescope system for SPICA, the next Japanese infrared astronomical satellite project. Details of our methodology for the ASTRO-F telescope, together with our optical test plan for the SPICA telescope, are reported.

Since the next cryogenic infrared mission "JAXA-SPICA" employs advanced mechanical cryocoolers with effective radiant cooling in place of cryogen, the primary mirror, 3.5 m in diameter, and the optical bench can be maintained at 4.5 K for at least 5 years. First, the feasibility of the thermal design of the cryogenic system is presented. A 20K-class Stirling cryocooler was then improved in cooling capacity and reliability for the mission, and the effects of contaminated working gas or new regenerator materials on cooling performance were investigated. Development of a new He-JT (Joule-Thomson) cryocooler for use at 1.7 K is also described, along with the successful results of a cooling capacity higher than the required 10 mW. A 4K-class cryocooler was modified and developed for higher reliability over a five-year operational life and a higher cooling capacity exceeding the current 30 mW. Finally, we discuss a system for heat rejection from cryocoolers using thermal control devices. 3

The Space Infrared Telescope for Cosmology and Astrophysics (SPICA) mission is the third Japanese astronomical infrared satellite project of a 3.5m cooled telescope optimized for mid- to far-infrared observations, following the Infrared Telescope in Space (IRTS) and the ASTRO-F missions. It will employ mechanical coolers and an efficient radiative cooling system, which allow us to have a cooled (4.5K) telescope of the aperture much larger than previous missions in space. The SPICA will attack a number of key problems in present-day astrophysics, ranging from the origin of the universe to the formation of planetary systems, owing to its high spatial resolution and unprecedented sensitivity in the mid- to far-infrared. The large aperture size for cryogenically use is, however, a great challenge and demands substantial technology developments for the telescope system. We adopt monolithic mirror design in the baseline model because of the technical feasibility and reliability. We set the optical performance requirement as being diffraction limited at 5μm at the operating temperature of 4.5K. The total weight attributed to the telescope system is 700kg, which requires a very light 3.5m primary mirror together with the mirror support structure. At present we are working on two candidate materials for the SPICA telescope: silicon carbide (SiC) and carbon-fiber reinforced silicon carbide (C/SiC). This presentation gives a general overview of the SPICA mission and reports the current design and status of the SPICA telescope system, including recent progress of the development of C/SiC mirrors.

One of the key technologies for next generation space telescope with a large-scale reflector is a material having high specific strength, high specific stiffness, low coefficient of thermal expansion and high coefficient of thermal conductivity. Several candidates such as fused silica, beryllium, silicon carbide and carbon fiber reinforced composites have been evaluated. Pitch-based carbon fiber reinforced SiC composites were developed for the SPICA space telescope mirror to comply with such requirements. Mechanical performance such as bending stiffness, bending strength and fracture toughness was significantly improved. Evaluation procedures of thermal expansion and thermal conductivity behavior at cryogenic temperatures (as low as 4.5K) were established and excellent performance for the SPICA mirror was demonstrated.

A two-stage small Stirling cooler has been developed and tested for the infrared astronomical satellite ASTRO-F that is planned to be launched by Japanese M-V rocket in 2005. ASTRO-F has a hybrid cryogenic system that is a combination of superfluid liquid helium (HeII) and two-stage Stirling coolers. The mechanical cooler has a two-stage displacer driven by a linear motor in a cold head and a new linear-ball-bearing system for the piston-supporting structure in a compressor. The linear-ball-bearing supporting system achieves the piston clearance seal, the long piston-stroke operation and the low frequency operation. The typical cooling power is 200 mW at 20 K and the total input power to the compressor and the cold head is below 90 W without driver electronics. The engineering, the prototype and the flight models of the cooler have been fabricated and evaluated to verify the capability for ASTRO-F. This paper describes the design of the cooler and the results from verification tests including cooler performance test, thermal vacuum test, vibration test and lifetime test.

SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is a future mission to launch a large infrared observatory to the second Sun-Earth Lagrangian liberation point (L2) by H-IIA rocket. A unique feature of its cryogenic system is a warm launch system using radiative cooling and closed-cycle mechanical coolers in orbit to cool its detectors and mirrors down to about 4.5 and 1.7 K. The 1 K-class cooler, which consists of a two-stage Stirling cooler and a Joule-Thomson (JT) cooler with He as the working fluid, has been developed for cooling the far infrared detectors to 1.7 K. Designed cooling capacity of the cooler is 10 mW at 1.7 K and the total input power to the cooler is about 180 W without driver electronics. This paper describes the preliminary design and the results from preliminary test of the prototype cooler for the 1 K-class cooler. © 2004 Elsevier Ltd. All rights reserved. 3

The Space Infrared Telescope for Cosmology and Astrophysics (SPICA) mission is a Japanese astronomical infrared satellite project optimized for mid-to far-infrared observations. It will be launched at ambient temperature and cooled down on orbit by mechanical coolers on board with an efficient radiative cooling system, which allow us to have a 3.5m cooled (4.5 K) telescope in space. SPICA will answer a number of important problems in present-day astronomy, ranging from the star-formation history of the universe to the formation of planets, owing to its high spatial-resolution and unprecedented sensitivity in the mid- to far-infrared. The large aperture mirror for cryogenically use in space, however, demands a challenging development for the telescope system. A single aperture design of the primary mirror will be adopted for the SPICA telescope rather than deployable mirror designs to avoid further complexity and ensure the feasibility. The number of actuators for the primary mirror, if needed, will be minimized. Silicon carbide and carbon-fiber reinforced silicon carbide are extensively investigated at present as the prime candidate materials for the SPICA primary mirror. This presentation reports the current status of the SPICA telescope system development.

Light-weight mirrors are developed for two Japanese infrared astronomical missions, ASTRO-F and SPICA. ASTRO-F is scheduled for launch in 2005, while the target year for launch of SPICA is 2010. The mirrors of the ASTRO-F telescope are made of a sandwich-type silicon carbide (SiC) material, comprising porous core and CVD coat of SiC on the surface. Cryogenic measurements of the ASTRO-F primary mirror and telescope assembly were performed extensively. As for the SPICA telescope, which has an aperture of 3.5-m diameter, carbon-fiber- reinforced SiC (C/SiC composite), as well as SiC, is one of the promising candidates for mirror material. C/SiC composite spherical test mirrors of 160-mm diameter has recently been manufactured and tested. This paper presents the experimental results of the cryogenic performance obtained for the sandwich-type SiC mirrors and the C/SiC composite mirrors.

The Submillimeter Probe of the Evolution of Cosmic Structure (SPECS) is a space-based imaging and spectral ("double Fourier") interferometer with kilometer maximum baseline lengths for imaging. This NASA "vision mission" will provide spatial resolution in the far-IR and submillimeter spectral range comparable to that of the Hubble Space Telescope, enabling astrophysicists to extend the legacy of current and planned far-IR observatories. The astrophysical information uniquely available with SPECS and its pathfinder mission SPIRIT will be briefly described, but that is more the focus of a companion paper in the Proceedings of the Optical, Infrared, and Millimeter Space Telescopes conference. Here we present an updated design concept for SPECS and for the pathfinder interferometer SPIRIT (Space Infrared Interferometric Telescope) and focus on the engineering and technology requirements for far-IR double Fourier interferometry. We compare the SPECS optical system requirements with those of existing ground-based and other planned space-based interferometers, such as SIM and TPF-I/Darwin.

We have examined the effects of transients, glitches caused by cosmic ray hits, and the crosstalk of the far-infrared detector arrays on-board ASTRO-F on its survey mode data. We used simple model fits to laboratory measurements for the transients and glitch profiles. We also tested several correction methods, based on these models, to recover the original signal. © 2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

We present the results of a wide-area mapping of the far-infrared continuum emission toward the Orion complex by using a Japanese balloon-borne telescope. The 155-μm continuum emission was detected over a region of 1.5 deg around the KL nebula with 3μ resolution similar to that of the IRAS 100-μm map. Assuming a single-temperature model of the thermal equilibrium dust, maps of the temperature and the optical thickness were derived from the 155-μm intensity and the IRAS 100-μm intensity. The derived dust temperature is 5-15 K lower and the derived dust optical depth is 5-300 times larger than those derived from the IRAS 60 and 100-μm intensities due to the significant contribution of the statistically heated very small grains to the IRAS 60-μ-m intensity. The optical-thickness distribution shows a filamentary dust ridge that has a 1.°5 extent in the north-south direction and well resembles the Integral-Shaped Filament (ISF) molecular gas distribution. The gas-to-dust ratio derived from the CO molecular gas distribution along the ISF is in the range 30-200, which may be interpreted as being an effect of CO depletion due to the photodissociation and/or the freezing on dust grains. 2