中川 貴雄

Low-noise and low-power cryogenic readout electronics are developed for a focal plane instrument of the IR Imaging Surveyor. We measured the static characteristics and the noise spectra of several types of silicon MOSFETs at the cryogenic temperature where silicon JFETs do not work well due to the carrier freeze-out. The 'kink' behavior of n- channel MOSFETs was observed below the carrier freeze-out temperature, but it was not obvious for the p-channel MOSFET. It was demonstrated the p-channel MOSFETs can be used for the cryogenic readout electronics of the IRIS's far-IR array with an acceptable performance. The amplifier integrated with these MOSFETs showed low-noise at 2K under a low power consumption of 1 (mu) W per MOSFET. We now design and evaluate several circuits that are fabricated by the CMOS process for cryogenic readout. ©2003 Copyright SPIE - The International Society for Optical Engineering.

Ge:Ga far-IR photoconductor 2D direct hybrid arrays are being developed for application in the focal-plane detectors of the far-IR surveyor, one of the two main instruments of the IR imaging surveyor satellite. The arrays are composed of Ge:Ga photoconductor arrays fabricated on one chip, Si- pMOS readout integrated circuits, and a hybridization of them done by using indium bump technology. ©2003 Copyright SPIE - The International Society for Optical Engineering.

The [CII] 158 mu m, [O I] 145 mu m and 63 mu m, [Si II] 35 mu m, and H-2 nu=O-O S(3) 9.7 mu m line emission from the rho Ophiuchi dark cloud has been observed in an one-dimensional raster scan in the east-west direction by the ISO/LWS and SWS. 32 raster points with spacing of 3.3' were observed. The raster scan was centered at 16(h)26(m), -24 degrees 28' (J2000) and the scan path included the B2 V star HD147889. The results clearly demonstrate spatial variations in the lines, which can be interpreted in terms of the cloud being illuminated in the direction orthogonal to the line of sight. The line intensity ratio of [O I] 145 mu m and [O I] 63 mu m implies that at least the [O I] 63 mu m Line is optically thick.

The sensitive all-sky survey in the far-infrared wavelength region will be achieved with a Far-Infrared Survey (FIS) instrument of Infra-Red Imaging Surveyor (IRIS) following the IRAS survey. It will be able to detect more than ten times fainter objects with better spatial resolution compared to the IRAS. The final point source catalog, which is expected to include distant ultra-luminous galaxies, starburst galaxies, proto-planetary disks, and so on, is undoubtedly important for the observatory-type infrared satellites, such as, SIRTF and FIRST. The launch of IRIS is scheduled in early 2003.

We made two sets of spectroscopic observations of fundamental rotation-vibration absorption spectra around 4.6 mu m of gas-phase CO toward the objects near the Galactic center and toward the Infrared Quintuplet near the Radio Are. The first set of observations was made with moderate resolution and clearly showed many absorption Lines at different rotation quantum numbers. The second set of observations was made with high resolution for each line and revealed various velocity components at each transition. On the basis of these observations, we determined column densities and temperatures of clouds in lines of sight. The two sets of observations showed consistent results and imply that that the mass of molecular clouds previously derived on the basis of the radio CO observations was significantly overestimated toward the Galactic center.

The Japanese satellite-borne infrared telescope, the Infrared Telescope in Space (IRTS), has completed a successful survey of a portion of the infrared sky. The IRTS consists of a 15 cm telescope cooled with superfluid liquid helium, and is installed on board the Space Flyer Unit (SFU) spacecraft. The SFU was launched on 1995 March 18 UT. The sky survey by the IRTS started on March 29 UT, and was completed on April 25 UT after exhausting its liquid helium. The cryogenic system operated as designed, and maintained the telescope and the focal-plane instruments at a stable temperature of 1.9 K for 38 days. The four focal-plane instruments, which together covered almost the entire infrared wavelength range, observed a sky area of about 2700 deg and returned a wealth of new data on a variety of objects, including the zodiacal light, interstellar gas and dust, near-infrared cosmic background light and point sources. 2

The 155 μm continuum emission from the galactic plane around l = 50° was observed with an 8′ × 13′ beam by the Far-Infrared Line Mapper (FILM) aboard the Infrared Telescope in Space (IRTS). The observed map noticeably resembles the IRAS 100 μm map. The dust temperature calculated from their flux ratio is almost constant (16-18 K) throughout the observed area, except for the H II regions. The dust temperatures in the H II regions are significantly higher than in the surrounding region; there is a clear boundary between the cold and hot regions. The observed uniformity of the dust temperature, except for in the H II regions, implies that the strength of the average interstellar radiation field (ISRF) along each line of sight is almost constant (i.e., varies by less than a factor of 2) in the observed region of the galactic plane.

The [C II] 158 μm line emission and the far-infrared continuum emission at 155 μm were observed by the Far-Infrared Line Mapper (FILM) aboard the Infrared Telescope in Space (IRTS) with its high sensitivity and resolution. The observation was made along a great circle crossing the galactic plane at l = 50° and 230°. Two components were found in their intensity distributions. The first component concentrates on the galactic plane. It is prominent on the plane at l = 50°, but is very faint at 230°. The second component extends over at least 20° in galactic latitude, and has nearly the same intensity at both crossing parts of the galactic plane. Therefore, the first one can be ascribed to emission from the galactic disk, and the second component to emission from the local interstellar gas. The intensity distribution of the [C II] line of the second component is similar to that of the HI 21 cm integrated intensity. This fact suggests that the local [C II] emission component arises in the HI 21 cm line emitting gas. From the ratio of the [C II] line luminosity to the hydrogen column density, the interstellar cooling rate of the HI gas is (5.6 ± 2.6) × 10 erg s /H-atom, corresponding to the cold neutral gas whose pressure is a few hundred cm K. -27 -1 -3

A detailed map of the distribution of the [C II] 158 μm line intensity from the galactic plane around l = 50° was obtained by the Far-Infrared Line Mapper (FILM) on board the Infrared Telescope in Space (IRTS). The distribution of the [C II] emission is similar to that of the far-infrared continuum emission. There are a number of discrete sources, most of which correspond to known objects, such as compact H II regions and molecular clouds, near to the galactic plane. Moreover, an extended component concentrated in the galactic plane was found, and its distribution does not clearly depend on the galactic longitude in the observed area. This extended component decreases rapidly as the galactic latitude increases. The FWHM of this component is about 2.°6 in the galactic latitude. This is larger than that of the CO (J = 1 → 0) intensity, but is much smaller than that of the H I 21 cm intensity.

The far-infrared line mapper (FILM) is a far-infrared spectrometer and in one of four focal plane instruments of the infrared telescope in space (IRTS), FILM was designed for wide area intensity mapping of far-infrared emission from interstellar gas and dust in the galaxy. The targets are the [CII] 158 micrometer line of the ionized carbon, the [OI] 63 micrometer line of the oxygen atom, and the continuum emission at 155 and 160 micrometer from the interstellar dust grain. A cylindrically concave varied line-space grating and a linear array of stressed Ge:Ga were successfully developed and allowed us to make a compact spectrometer compatible to severe limitations of the small cryogenic telescope. The IRTS, onboard the space flyer unit (SFU), was launched by a HII rocket on March 18, 1995 and was recovered by a STS on January 13, 1996. The FILM worked very well during four weeks allocated for the IRTS observation and produced a lot of valuable data. The sensitivity and the spatial resolution for the [CII] line are an order of magnitude better than the previous work.

We have developed an eight-element stressed Ge:Ga linear array. It has a compact and stable structure. The pixel size is 0.9 x 0.9 x 0.9 mm , the pitch of the array is 1.0 mm, and the total sensitive area is 8.0 mm x 1.0 mm. The longer wavelength cut-off is 200 microns, and the peak responsivity is 100 A/W in a high-background condition including cavity efficiencies. It has been demonstrated that this array has a useful performance in the high-background condition, such as for air-borne and balloon-borne instruments. The structure of the stress assembly is provably extendable up to sixteen and more. 3

The Infrared Telescope in Space (IRTS) is a cryogenically cooled small infrared telescope that will fly aboard the small space platform Space Flyer Unit. It will survey approximately 10% of the sky with a relatively wide beam during its 20 day mission. Four focal-plane instruments will make simultaneous observations of the sky at wavelengths ranging from 1 to 1000 μm,. The IRTS will provide significant information on cosmology, interstellar matter, late-type stars, and interplanetary dust. This paper describes the instrumentation and mission.

We have developed a Far-Infrared Line Mapper (FILM) as one of the four focal plane instruments on the Infrared Telescope in Space (IRTS). The FILM is a grating spectrometer designed to simultaneously measure [C II] 158 μm and [O I] 63 μm line intensities and continuum emission near the [C II] line with spatial resolution of 8 arcmin. Very high sensitivity and accuracy are achieved by using stressed and unstressed Ge: Ga detectors at 1.8 K with a helium cooled telescope and by using a spectral scanner to distinguish the line emission from the continuum emission. Line intensities of the [C II] and the [O I] will be mapped over 10% of the sky with much higher sensitivity than the previous survey measurements.

Using the balloon-borne infrared telescope (BIRT) incorporated with a liquid-helium-cooled double-channel Fabry-Perot spectrometer, intensities and velocity profiles of [C II] 158 μm and [O I] 63 μm fine-structure lines have been observed in the Galactic center region within |l| ≦ 0°.7. Intense [C II] line emission has been detected ubiquitously in almost all of the observed points. The distribution of the [ C II] intensity shows a central peak at Sgr A West together with two prominent peaks at Δ1 = ± 0°.6, which correspond to Sgr B1 (not Sgr B2) and Sgr C, respectively. The intensity distribution resembles but is not identical to, that of far-infrared emission. The velocity profiles of the [C II] line are resolved and can be deconvolved into multiple components, many of which can be traced to the features observed by molecular lines. The [O I] 63 μm line has been detected at Sgr A West and at some other points. The [O I] 63 μm/[C II] 158 μm ratios are always less than 3 in the beam of 3′.7. These observed results can be explained as the emission generated in photodissociation regions formed in the molecular clouds complexes illuminated by intense UV radiation field in the Galactic center regions. However, contribution from ELD region is possibly present and cannot be ruled out.

By using a balloon borne telescope, an extensive survey of the [CII] line emission of the Galaxy has been undertaken. To minimize the instrumental emission, an off-axis telescope with a Newtonian-Nasmyth focus was used in conjunction with a liquid helium cooled Fabry-Perot spectrometer. The beam size of the telescope was 12' in diameter and the spectral resolution of the spectrometer was 175 km/s in velocity scale. The balloon flights were made from Palestine, TX in 1991 and from Alice Springs, Australia in 1992. By both observations, the major part of the galactic plane in the northern sky and the southern sky has been scanned. As a result, a complete map of the [CII] line intensity distribution has been constructed for the region from-100° to 80° in galactic longitude and within ±4° in galactic latitude. In addition to the general scan of the galactic plane, the observations were extended to some individual sources, such as Cyg-X region, p-Oph dark cloud and Large Magellanic Cloud. The observed maps reveal strong [CII] line emission extensively distributed in the galactic plane, as well as many discrete sources associated with HII regions and/or molecular clouds. The distribution is more or less correlated with far infrared continuum and CO line intensity distributions. However, detailed comparisons show interesting differences between the three components. © 1994.

A detailed map of the [C II] 158 μm line emission from the ρ Ophiuchi dark cloud has been obtained using a balloon-borne telescope (BICE). The [C II] emission is extended throughout the cloud (8 pc × 6 pc), indicating that UV radiation in the cloud is not localized but is ubiquitously distributed. The peak of the emission corresponds to the position of the highly reddened B2 V star HD 147889. The ratio I //I in the ρ Ophiuchi cloud is higher than those found in active star-forming regions with O-type stars, which indicates a higher gas heating efficiency in the ρ Ophiuchi cloud. Since the scale length of the [C II] emission in the core region is much larger than that expected in homogeneous clouds, the cloud structure must be highly clumpy to allow UV radiation to penetrate the cloud and form an extended C region. [C II] bol +

Interstellar [CII] and [OI] lines have been observed by the Balloon-Borne Infrared Telescope (BIRT) in corporation with a Fabry-Perot spectrometer. Two balloon flights were successfully made from Palestine, Texas in May/June 1988. With a new method of "frequency switching", diffuse [CII] line emission was efficiently detected and mapped in extended regions around HII/molecular cloud complexes and in a wide area of the Galactic plane. It has been shown that the [CII] emission is very strong and ubiquitously distributed in interstellar space in the Galaxy. © 1992.

The research on C/C composites reached the step of practical application to engineering materials into many countries in the world. C/C composites show high specific strength in compared with other materials. It has strongly requirement as importance materials for structural materials of space plane and air craft. C/C composites are small thermal expansion, excellent heat impact resistance and high temperature strength, except that it is oxidation resistance. We have been research and development on air turbo ramjet engine which is to intend use for space plane (Ultra-high speed air craft). Carbon fiber reinforced carbon matrix turbine blade that produced by hot pressing the special-designed preformed yarn have been examine under the actual loading and rotor. The objective of this experiment is for obtained the information on the environment resistance (above 30.000 rpm, test atmosphere 70% H , 30% H O) of ACC turbine blade. That is difference of fabrication method, difference of fiber orientation and weaving method which is structural member of C/C composite blade. Test results show that the fracture behaviors of C/C composite turbine blade are strongly dependent on the weaving orientation of carbon fibers. 2 2

A stressed Ge:Ga photoconductor array with three elements applied to the Infrared Telescope in Space satellite was fabricated and tested in experiments at 2.0 K in very low-photon-influx conditions (˜ 10 photons/s). Stress was applied to three Ge:Ga detectors in a series by a stable and compact stressing apparatus by using cone-disk springs. The cutoff wavelength was ˜ 180 μm. Responsivity was ˜ 100 A/W, and the product of quantum efficiency and photoconductive gain, t)G, was ˜ 1 with a chopping frequency of 2 Hz. The noise equivalent power was < 5 x HT W/Hz when low-noise transimpedance amplifiers were used. A slow transient response and a nonlinear response that was dependent on the background photon influx were observed in the experiments. The latter showed that the -ȠG had a time constant tc that was proportional to N . © 1992 Optical Society of America. 5 18 1/2 -1/2 ph

Japan's spacecraft PLANET-B will be sent to the Mars in 1996. We are proposing the Martian ionosphere and the magnetosphere imaging using the extreme ultra violet (EUV) light on this mission. Our main target is the 84.3 nm light scattered by the oxygen ions. Interesting topics related to the imaging are; (1) the density profile of the oxygen ions in the Martian ionosphere, (2) oxygen ions which are reported to outflow from the nightside ionosphere to the Martian tail with about 1 keV energy, and (3) pick-up ions created at the dayside of the Mars. Also proposed is the measurement of the EUV light scattered by Helium ions in the interplanetary space during the cruise phase from the Earth to the Mars.

A diffuse far-infrared [C II] emission line has been detected in an extensive region (30° ≤ l ≤ 51°) along the Galactic plane. The [C II] line is bright and extended far from discrete luminous H II regions. Latitudinal and longitudinal profiles of the [C II] intensity distribution are quite similar to those of CO(J = 1-0) and the 100 μm continuum, but are completely different from those of H I 21 cm. The diffuse [C II] emission probably comes from the photodissociated C regions enveloping giant molecular clouds exposed to the general interstellar UV radiation field. The extended low-density ionized gas might also contribute to the diffuse [C II] emission. The mass of the C regions may be as much as 35%-50% of that of CO molecular gas. The total luminosity of the [C II] line emitted from the inner Galactic disk amounts to 2.8(±1.1) × 10 L , or about 0.36 % of the total far-infrared luminosity of the same region. 12 + + 7 +0.28 ⊙ -0.17

A wobbling mechanism for a secondary mirror has been developed for a balloon-borne infrared telescope. Friction of the wobbling mechanism is negligibly small, and hence the wobbling mechanism is very reliable for the use in a severe environment at balloon altitudes. Motion is controlled by servo electronics, whose transfer function includes the second-order differential term of the error signal in order to improve the waveform. Good performance of the drive mechanism has been confirmed in two balloon flights in 1988 at an altitude of 31 km.

A compact cluster of five luminous infrared sources has been found in the vicinity of the Galactic center radio arc. All of the sources have large polarizations in the near-infrared and deep silicate absorptions at 10 μm. Strong absorption lines of CO are seen at 4.6 μm toward each source. The observed polarization and spectral features are likely to be interstellar in origin. The temperatures of the sources, based on infrared photometry and corrected for extinction, are in the range 600-900 K. None of the sources show either infrared recombination line emission from atomic hydrogen, lines of molecular hydrogen, or overtone band of CO at 2.3 μm. Because the objects are tightly clustered, all are likely to be very young objects; however, accurate classifications cannot be made at the present time.

A stressed Ge:Ga photoconductor array with 3 elements has been developed for the Infrared Telescope in Space (IRTS) satellite of Japan. The detectivity was very high at low temperature and under low infrared background. Nonlinear response dependent on photon influx was observed in the experiments and the phenomenon is discussed in the paper.

We have developed a Fabry-Perot spectrometer for far-infrared spectroscopic observations on the Balloon-borne Infrared Telescope (BIRT ). The spectrometer consists of two independent channels for simultaneous observations of two lines, and each channel is composed of two tandem Fabry-Perot interferometers. All the optical components, including the interferometers, are cooled down to 2K with super-fluid liquid helium. We have employed two modes of observations: (1) the frequency switching mode with spatial scanning, and (2) the conventional spatial chopping mode with fixed pointing. The former mode is especially suitable to observe spatially extended emission because the mode dose not require spatial chopping. We have made two successful flights in 1988 with our observing system. For the [CII] (158μm) line, the system NEP was measured to be 1 × 10 W Hz , and the spectral resolving power was 2100. We observed many kinds of objects during the flights, and the frequency switching method was proved to be very efficient to observe extended sources. 1 -14 - 1/2

The Balloon-Borne Infrared Telescope (BIRT) has been developed for far-infrared astronomy by a joint project between the Institute of Space and Astronautical Science (ISAS) and Kyoto University in Japan. It has a 50 cm reflector telescope mounted on an alt-azimuthal pointing system actuated by a control-moment gyro (CMG) torquer in the azimuth. The pointing and tracking are accomplished by a unique offset guide system which utilizes a star tracker and a star field camera mounted on a two-axis offset gimbals. The motion of the gimbals is controlled by an on-board CPU which computes and corrects the rotation rate of the offset direction caused by the celestial diurnal motion as well as the horizontal motion of the balloon gondola. BIRT has been flown 6 times at Alice Springs, Australia in 1985 and 1986, and 2 times at Palestine, Texas in 1988. The pointing and tracking accuracies were less than 1 arcmin, and the peak-to-peak attitude stability was smaller than 30 arcsec in those flights. The last two flights, at which liquid helium cooled Fabry-Perot spectrometer was mounted on the Nasmyth focus, were quite successful for observing far-infrared spectral lines ([CII] 158 μm and [OI] 63 μm) over wide areas of several galactic nebula and Milky Way. These observations have demonstrated that balloon-borne observation is a quite useful method for far-infrared spectroscopy.

Sensitive far infrared stressed Ge:Ga photoconductors which have response up to 200μm wavelength have been fabricated and studied to apply them to astronomical and atmospherical observations using balloons and satellites. The stressed Ge:Ga photoconductors have shown very high detectivity, i.e. responsivity of 15 A/W and NEP = 2 × 10 W/√Hz when operated at 2 K and at photon fluxes 1.1 × 10 photons/s, and the stable stress operation has been achieved by using the compact stressing mechanism with cone disk springs. The good performance has been confirmed by balloon experiments to detect astronomical CII line at 157.7 μm. © 1989. -18 6

A far infrared monochromator of Czerny-Turner type has been devised which has an output optical system comprising two small spherical mirrors to obtain non-astigmatic image. The far infrared monochromator covers both 50-120 urn and 100-240 urn wavelengths ranges and can be used to measure spectral response of stressed Ge:Ga photoconductors having response up to 200 urn, which we have fabricated to apply them to far infrared astronomical observations by balloons and by sattelites. Experimental performance of the stressed Ge:Ga photoconductors under low photon fluxes conditions also will be given.

For high resolution spectroscopic observations in infrared astronomy, liquid helium cooled Fabry-Perot spectrometers have been developed. Making the spectrometers as simple and sturdy as possible, we have realized compact and stable spectrometers useful for even harsh conditions as in balloon or space observations as well as in ground based observations. © 1986 SPIE.