Hazard and Risk Assessment (HARA) is a critical Systems Engineering and safety activity used to ensure a safe environment for personnel and hardware. This paper discusses how TMT has tailored the Atlassian Jira tool and third-party embedded app, SoftComply Risk Manager, to provide a collaborative environment with subsystem teams in order to a develop a comprehensive HARA, starting with hazard identification and assessment and continuing through reassessment after mitigation. The paper shows how the tool was initially created for the Telescope Structure (STR) to facilitate collaboration with the National Astronomical Observatory of Japan (NAOJ) and Mitsubishi Electric Corporation (MELCO), and has since expanded to other subsystems as well as to the system-level, capturing intersystem hazards. From the system and subsystem HARAs, risk reduction actions are identified and if safety functions are used as a mitigation, they are described in terms of functional safety actions and associated SIL ratings. These safety functions are then traced to safety requirements imposed on the Observatory Safety System or on subsystems. This overall HARA process provides TMT with a comprehensive overview of all Observatory hazards and the status of the development and implementation of their mitigations thanks to the Jira and Risk Manager dashboards, risk matrix, and risk table views.
Wide-field-of-view millimeter-wave telescopes have been developed for astronomical observations, such as cosmic microwave background (CMB) polarimetry. These telescopes often employee phase-insensitive detectors that are fabricated with the on-chip feed antennas. A holographic field-retrieval method is useful for near-field antenna measurements of such telescopes. Among several variations of the methods, we present the one using the phase shifting of the reference waves, which do not require a fine frequency sweeping. This method aims at application to the ground testing of the LiteBIRD Low-Frequency Telescope (LFT) antenna, which observes the CMB and foreground radiations at 34–161 GHz. In our experiments conducted with a LFT 1/4-scaled antenna, the new method indicated an accuracy of −56 dB levels, which is required for the sidelobe levels of the LFT.
The development of millimeter-wave absorbers for astronomical instruments is an important area of research regarding stray light suppression. Millimeter-wave absorbers for space missions should be selected based not only on their broadband performance at oblique incidence but also on their polarization characteristics, weight, and radiation tolerance. LiteBIRD is a space telescope designed to test inflationary theories by observing the polarization of the cosmic microwave background (CMB). The Low-Frequency Telescope (LFT) on board LiteBIRD needs to know the far side lobes at the −56 dB level, so surrounding it with millimeter-wave absorbers suppresses stray light. Because even the smallest stray light reflection may cause non-negligible far side lobes in the millimeter-wave absorber inside the telescope, it is necessary to accurately measure the reflectance of the millimeter-wave absorber not only specular reflection but also diffuse reflection. We performed near-field reflection measurements of a new lightweight absorber for two polarizations with a 30 degree angle of incidence in the frequency range between 70 GHz and 110 GHz. Measurements showed a reflectance of -16 dB for TE and -19 dB for TM, lower than the industry standard Eccosorb AN-72. In addition, we evaluated radiation tolerance and confirmed that the difference in reflectance before and after exposure was within 3 dB.
KEYWORDS: Antennas, Near field, Holography, Telescopes, Phase measurement, Holograms, Polarization, Detector arrays, Near field optics, Signal detection
Wide field-of-view millimeter-wave telescopes with a bolometric detector array have been developed for cosmic microwave background radiation observations. For the purpose of laboratory verification of these telescopes, several studies have demonstrated near-field antenna measurements using a phase-sensitive detector that replaces a few representative pixels of the focal-plane detector array. We present a holographic phase-retrieval method that enables near-field measurements with the bolometric detector array as it is. We place a reference emitter at a fixed position and scan a signal emitter at the telescope aperture. These two emitters are phase-locked and generate interference patterns (holograms) on the focal plane, from which the amplitude and phase of the aperture field can be retrieved. We experimentally demonstrated this method with a crossed-Dragone telescope with a field-of-view that is 18 deg × 9 deg. In the demonstration, we placed a phase-sensitive detector at three detector positions on the focal plane. The antenna patterns calculated from the hologram, neglecting the directly measured phase information, were consistent with those calculated from both intensity and phase measurements at the −60-dB level at 180 GHz. Applying this method, the antenna patterns for all of the bolometric detectors on the focal plane can theoretically be measured simultaneously.
LiteBIRD is a space mission intended for the late 2020s that aims to observe the large-angular-scale polarization pattern of the cosmic microwave background. The low-frequency telescope (LFT) aboard LiteBIRD has a crossed-Dragone design and observes at 34 to 161 GHz with a field of view (FoV) of 18 deg × 9 deg. The LFT antenna optics is predicted to induce polarization angle rotation by up to around 1.5 deg in its FoV, while polarization angles among the detectors should be corrected to a few arcminutes level to distinguish E- and B-mode polarizations. To characterize the polarization angle rotation by the antenna optics and to develop a ground calibration method, we performed polarization angle measurements with a small compact-antenna-test-range setup. We measured the polarization angles of a 1/4-scaled LFT antenna across the FoV at correspondingly scaled frequencies of 140 to 220 GHz (35 to 55 GHz for the full-scale LFT). We placed a collimated-wave source near the scaled-LFT aperture and rotated the scaled-LFT feed polarization. The measured polarization angles agree with those measured by rotating the collimated-wave polarization at the 15″ level for the on-axis case. The measurements are consistent with simulation and determined the polarization angles with an uncertainty of less than 1.9′.
We verified a method of near-field antenna pattern measurement for a wide-field telescope with a bolometric detector array, based on a holographic phase-retrieval technique. A signal emitter scans the telescope aperture and a reference emitter, which is phase-locked to the signal, is located at a fixed position to allow a bolometric detector to receive the both. It generates a hologram on the focal plane as a function of the signal emitter location. Since the hologram is obtained in a receiving mode, we can use the telescope-equipped detector as it is. It is beneficial for the case where such detector is integrated with a feed antenna, which characterizes the telescope performance. The new method also has an advantage that we do not need the phase calibration of the reference emitter since it is constant. We experimentally demonstrated this method with a crossed-Dragone antenna whose field of view is 18◦ × 9 ◦ at 180 GHz for three representative detector positions in the focal plane. The antenna patterns were consistent with those measured by a vector near-field measurement at the level of −60 dB, which directly acquires both the phase and the amplitude of the electric field.
Suppression of straylight is one of the challenges in the optical design of a wide-field-of-view telescope. It contaminates the weak target signal with radiation from strong sources at angles far from the observing direction. We evaluated the optical design of a crossed-Dragone telescope, the LiteBIRD Low-Frequency Telescope (LFT), which has 18° ×9° field of view. We measured a 1/4-scaled antenna of the LFT at accordingly scaled frequencies of 160–200 GHz (corresponding to 40–50 GHz for the full-scale LFT), for the feed at the center and the edges of the focal plane. To separate straylight components, we computed the time profiles of the aperture fields with ∼ 0.1 ns resolution by inverse Fourier transformation of the measured frequency spectra and applied time gating to them. We identified far-sidelobe components in the time-gated antenna beam patterns whose arrival time and angular direction are consistent with straylight predicted by a ray-tracing simulation. The identified far-sidelobe components include straylight reduced but reflected inside the front hood and straylight with multiple reflections without intercepted by the front hood. Their intensities are less than the −56 dB level, which is the far-sidelobe knowledge requirement for the LFT.
LiteBIRD is JAXA Strategic Large Mission for the late 2020s that aims to observe the large-scale B-mode polarization pattern of the cosmic microwave background. One of its telescopes, the Low Frequency Telescope (LFT), has a crossed-Dragone design and observes at 34-161 GHz with a field of view of 18° x 9°. Because a miscalibration of the polarization angles mixes E- and B-mode polarization, we have measured the variation of the polarization angles in the field of view of a 1/4-scaled LFT antenna at 140-220 GHz, which corresponds to 35-55 GHz for the full-scale LFT, considering a scaling of the wavelength. We placed a collimated-wave source near the scaled-LFT aperture and rotated the polarization angle of the LFT feed. The measurements were explained well with a simple Jones matrix calculation, and the fitting errors of the polarization angles were less than 0.1’. We also measured the polarization angles by rotating the polarization direction in the scaled-LFT aperture, and the results were consistent with the angles measured by rotating the feed polarization at the ±10” level, except at the lowest frequencies. The polarization angle at the edges of the focal plane varied from that at the center by up to around a degree, with larger variation at lower frequencies. We evaluated the polarization angles for both Pol-X and Pol-Y feeds, and the results with Pol-Y showed a trend consistent with ray-tracing simulations. The results for Pol-X showed the opposite trend of the polarization rotation direction and larger angle variations.
The Lite satellite for the studies of B-mode polarization and Inflation from the cosmic microwave background
(CMB) Radiation Detection (LiteBIRD) is a next generation CMB satellite dedicated to probing the inflationary
universe. It has two telescopes, Low Frequency Telescope (LFT) and High Frequency Telescope (HFT) to cover
wide observational bands from 34 GHz to 448 GHz. In this presentation, we report the optical design and
characterization of the LFT. We have used the CODE-V to obtain the LFT optical design based on a cross-
Dragonian telescope. It is an image-space telecentric system with an F number of 3.5 and 20 x 10 degrees2 field
of view. The main, near and far side lobes at far-field have been calculated by using a combination of HFSS and
GRASP 10. It is revealed that the LFT telescope has good main lobe properties to satisfy the requirements. On
the other hand, the side lobes are affected by the stray light that stems from the triple reflection and the direct
path from feed. In order to avoid the stray light, the way to block these paths is now under study.
LiteBIRD is a next generation satellite aiming for the detection of the Cosmic Microwave Background (CMB) B-mode polarization imprinted by the primordial gravitational waves generated in the era of the inflationary universe. The science goal of LiteBIRD is to measure the tensor-to-scaler ratio r with a precision of δr < 10-3♦, offering us a crucial test of the major large-single-field slow-roll inflation models. LiteBIRD is planned to conduct an all sky survey at the sun-earth second Lagrange point (L2) with an angular resolution of about 0.5 degrees to cover the multipole moment range of 2 ≤ ℓ ≤ 200. We use focal plane detector arrays consisting of 2276 superconducting detectors to measure the frequency range from 40 to 400 GHz with the sensitivity of
3.2 μK·arcmin. including the ongoing studies.
We present the mission design of LiteBIRD, a next generation satellite for the study of B-mode polarization and inflation from cosmic microwave background radiation (CMB) detection. The science goal of LiteBIRD is to measure the CMB polarization with the sensitivity of δr = 0:001, and this allows testing the major single-field slow-roll inflation models experimentally. The LiteBIRD instrumental design is purely driven to achieve this goal. At the earlier stage of the mission design, several key instrumental specifications, e.g. observing band, optical system, scan strategy, and orbit, need to be defined in order to process the rest of the detailed design. We have gone through the feasibility studies for these items in order to understand the tradeoffs between the requirements from the science goal and the compatibilities with a satellite bus system. We describe the overview of LiteBIRD and discuss the tradeoffs among the choices of scientific instrumental specifications and strategies. The first round of feasibility studies will be completed by the end of year 2014 to be ready for the mission definition review and the target launch date is in early 2020s.
KEYWORDS: Telescopes, Optical instrument design, Computer aided design, Mirrors, Electroluminescence, Control systems design, Control systems, Earthquakes, Safety, Thirty Meter Telescope
We present an overview of the preliminary design of the Telescope Structure System (STR) of Thirty Meter Telescope (TMT). NAOJ was given responsibility for the TMT STR in early 2012 and engaged Mitsubishi Electric Corporation (MELCO) to take over the preliminary design work. MELCO performed a comprehensive preliminary design study in 2012 and 2013 and the design successfully passed its Preliminary Design Review (PDR) in November 2013 and April 2014. Design optimizations were pursued to better meet the design requirements and improvements were made in the designs of many of the telescope subsystems as follows: 1. 6-legged Top End configuration to support secondary mirror (M2) in order to reduce deformation of the Top End and to keep the same 4% blockage of the full aperture as the previous STR design. 2. “Double Lower Tube” of the elevation (EL) structure to reduce the required stroke of the primary mirror (M1) actuators to compensate the primary mirror cell (M1 Cell) deformation caused during the EL angle change in accordance with the requirements. 3. M1 Segment Handling System (SHS) to be able to make removing and installing 10 Mirror Segment Assemblies per day safely and with ease over M1 area where access of personnel is extremely difficult. This requires semi-automatic sequence operation and a robotic Segment Lifting Fixture (SLF) designed based on the Compliance Control System, developed for controlling industrial robots, with a mechanism to enable precise control within the six degrees of freedom of position control. 4. CO2 snow cleaning system to clean M1 every few weeks that is similar to the mechanical system that has been used at Subaru Telescope. 5. Seismic isolation and restraint systems with respect to safety; the maximum acceleration allowed for M1, M2, tertiary mirror (M3), LGSF, and science instruments in 1,000 year return period earthquakes are defined in the requirements. The Seismic requirements apply to any EL angle, regardless of the operational status of Hydro Static Bearing (HSB) system and stow lock pins. In order to find a practical solution, design optimization study for seismic risk mitigation was carried out extensively, including the performing of dynamic response analyses of the STR system under the time dependent acceleration profile of seven major earthquakes. The work is now moving to the final design phase from April 2014 for two years.
The ACA (Atacama Compact Array) system is an important element of ALMA and consists of four ACA 12-m antennas
and twelve ACA 7-m antennas. The ACA system aims to acquire the total power data with four 12-m antennas and the
short baseline interferometer data with 7-m antennas. The ACA system also increases reliability of the interferometer
maps of astronomical sources larger than the field view of the 12-m antenna. The science performance of these antennas
has been extensively verified at OSF (operation support facility) at an elevation of 2900 m in Atacama desert in northern
Chile since 2007. The pointing performance has been verified with a dedicated optical pointing telescope, the servo
performance is tested with angle encoders, and the surface accuracy has been measured with a radio holography method.
Both ACA 12-m antennas and 7-m antennas have been successfully demonstrated to meet the very stringent ALMA
specifications.
The POrtable Submillimeter Telescope (POST) was put into operation in Nov. 1999. In this paper, we briefly introduce the control system of the telescope, including both hardware and software. The hardware is based on the S-Bus of a SUN workstation. Industrial standard I/O interfaces are adopted to fulfil different purposes of information transfer. Pulse width modulation (PWM) and harmonic driver are adopted to the antenna driving system, which is controlled in a mode of closed-loop positional feedback. The control software is to accomplish various observing and diagnostic functions of the telescope. The software is designed as a centralized real-time, multi-task package on the base of the UNIX platform. Present version of the entire control software includes 14,000 lines of source code in C language. The control system as a whole realizes all functions of a highly automatic all-sky submillimeter telescope used to observe cosmic submillimeter line radiation, particularly the neutral atomic carbon line at 492GHz. Besides, the system can be operated remotely. The principle as well as the software can be applied to control other precision radio telescopes.
This paper reports on a space-qualified cooling system for submillimeter SIS mixer receiver (SIS: superconductor- insulator-superconductor). Designed cooling capacity of the system is 20 mW at 4.5 K, 200 mW at 20 K, and 1000 mW at 100 K. The combination of two-stage Stirling cooler and Joule- Thomson one has demonstrated the capacity with a power consumption of less than 300 W, including losses of drive electronics. The cryostat has a thermal insulation structure of S2-GFRP straps to fasten its 100 K stage. 20 K stage of the cryostat is held with GFRP pipes on the 100 K stage, while 4 K stage is supported with CFRP pipes on the 20 K stage. The cooling system accommodates two SIS mixers at 4.5 K, two IF amplifiers at 20 K, and two more IF amplifiers at 100 K. The mass of the cooling system is 40 kg for the mechanical cooler itself, 26 kg for the cryostat, and 24 kg for the driver electronics. The system has been developed for a 640 GHz receiver for an atmospheric limb-emission sounder SMILES, which is to be aboard the International Space Station in 2005. The engineering model of the system has been built and tested successfully.
A submillimeter wave limb emission sounder, that is to be aboard the Japanese Experiment Module (JEM, dubbed as 'KIBO') at the International Space Station, has been designed. This payload, Superconducting Submillimeter-wave Limb Emission Sounder (SMILES), is aimed at global mappings of stratospheric trace gasses by means of the most sensitive submillimeter receiver ever operated in space. Such sensitivity is ascribed to a Superconductor-Insulator- Superconductor (SIS) mixer, which is operated at 4.5 K in a dedicated cryostat combined with a mechanical cooler. SMILES will observe ozone-depletion-related molecules such as ClO, HCl, HO2, HNO3, BrO and O3 in the frequency bands at 624.32 - 626.32 GHz, and 649.12 - 650.32 GHz. A scanning antenna will cover tangent altitudes from 10 to 60 km in every 53 seconds, while tracing latitudes from 38S to 65N along its orbit. This global coverage makes SMILES a useful tool of observing the low- and mid-latitudinal areas as well as the Arctic peripheral region. The molecular emissions will be detected by two units of acousto-optic spectrometers (AOS), each of which has coverage of 1.2 GHz with a resolution of 1.8 MHz. This high-resolution spectroscopy will allow us to detect weal emission lines attributing to less-abundant species.
A submillimeter limb-emission sounder, that is to be aboard the Japanese Experiment Module (JEM, dubbed as KIBO) at the International Space Station, has been designed. This payload, Superconducting Submillimeter-wave Limb-emission Sounder (SMILES), is aimed at global mappings of stratospheric trace gases by means of the most sensitive submillimeter receiver ever operated in space. Such sensitivity is ascribed to a Superconductor-Insulator- Superconductor (SIS) mixer, which is operated at 4.5 K in a dedicated cryostat combined with a mechanical cooler. SMILES will observe ozone-depletion-related molecules such as ClO, Hcl, HO2, HNO3, BrO and O3 in the frequency bands at 624.32-626.32 GHz and 649.12-650.32 GHz. A scanning antenna will cover tangent altitudes from 10 to 60 km in every 53 seconds, while tracing the latitudes form 38 S to 65 N along its orbit. This global coverage makes SMILES a useful tool of observing the low- and mid- latitudinal areas as well as the Arctic peripheral region. The molecular emissions will be detected by two units of acousto-optic spectrometers (AOS), each of which has coverage of 1.2 GHz with a resolution of 1.8 MHz. This high-resolution spectroscopy will allow us to detect weak emission lines attributing to less-abundant species.
KEYWORDS: Spectroscopy, Adaptive optics, Acousto-optics, Interference (communication), Charge-coupled devices, Analog electronics, Signal to noise ratio, Spectroscopes, Quantization, Data modeling
An acousto-optical spectrometer (AOS) is employed in order to meet scientific mission objectives of submillimeter-wave limb-emission sounder (SMILES) to be aboard the Japanese Experiment Module (JEM) of the International space station (ISS). The capability of multi channel detection with AOS is suitable for observing multi chemical species in a wide frequency region. Wide noise dynamic range enables us to obtain the spectra without unnecessary increase of system noise, suggesting a good combination of AOS with low noise front end system of SMILES> Several technical concerns relating to important instrumental characteristics of AOS are discussed and expected performance of the spectrometers to be used in the JEM/SMILES mission are over viewed.
KEYWORDS: Space operations, Data processing, Data centers, Algorithm development, Data archive systems, Multiplexing, Satellites, Data backup, Binary data, Relays
Superconducting sub-millimeter-wave limb-emission sounder (SMILES) using 4K Superconductor-Insulator-Superconductor (SIS) detector for ISS/JEM is under development. Spectrum of 600 GHz regions will be acquired using acousto-optics spectrometer (AOS). The high sensitivity of SMILES will enable us to measure O3, ClO without enhancement, BrO, Hcl, HO2, HNO3 from 10 to 60 km. This paper describes a current plan of data retrieval algorithms (L0, L1, L2 and L3), ground data system, data validation and data distribution.
In order to estimate measurement capability of the Superconducting Submillimter-Wave Limb-Emission Sounder (SMILES) on the Japanese Experiment Module (JEM) of the International Space Station (ISS) and to clarify the scientific impacts of the JEM/SMILES, we are developing the JEM/SMILES simulator. The simulator consists of the forward model and the inversion model. The forward model calculates a brightness temperature by applying the radiative transfer formula to a limb sounding geometry and simulates the effects of the JEM/SMILES sensor characteristics including optics superconductor-insulator-superconductor (SIS) mixers, Acousto-Optical Spectrometer (AOS), and so on, to it. Because it is important to estimate the effects of the sensor for the retrieval, we develop carefully simulated sensor model. The forward model also calculates weighting functions of molecular, the temperature, the pressure and so on. This paper describes how the brightness temperature and weighting functions are calculated in the forward model and how the effects of the sensor are taken into account in the simulator, and finally shows how the optical estimation method (OEM) is applied to our retrieval model.
An engineering model has been built for a space-borne 640- GHz SIS receiver. It is the key component of Superconducting Submillimeter-Wave Limb-Emission Sounder, which is to be operated aboard the Japanese Experiment Module of the International Space Station in 2005. The receiver includes two Superconductor-Insulator-Superconductor (SIS) mixers cooled at 4.5 K, as well as four High-Electron-Mobility- Transistor (HEMT) amplifiers, two of which cooled at 20 K and the other two at 100 K. These components are integrated in a compact cryostat with two-stage Stirling and Joule- Thomson refrigerators. The receiver components has been successfully cooled and the cryostat has survived random vibration tests. The 640-GHz SIS mixer, which uses a pair of Nb/AlOx/Nb junctions connected in parallel, is built so that a broad RF matching be achieved without mechanical tuners. It is followed by cooled low noise HEMT amplifiers with a noise temperature of less than 17 K. The total receiver noise temperature has been measured around 180 - 220 K over the bandwidth of 5.5 GHz.
The Mt. Fuji submillimeter-wave telescope has been operated since November 1998 to survey neutral atomic carbon (CI) toward the Milky Way. It has a 1.2 m main reflector with a surface accuracy of 10 micrometer in rms. A dual polarization superconductor-insulator-superconductor (SIS) mixer receiver mounted on the Nasmyth focus receives 810/492/345 GHz bands in DSB simultaneously. An acousto-optical spectrometer (AOS) has 1024 channels for 0.8 GHz bandwidth. The telescope was installed with a helicopter and bulldozers at the summit of Mt. Fuji (alt. 3725 m) in July 1998 after a test operation at Nobeyama for a year. It has been remotely operated via a satellite communication from Tokyo or Nobeyama. Atmospheric opacity at Mt. Fuji was 0.4 - 1.0 at 492 GHz in 30% of time and 0.07 - 0.5 at 345 GHz in 60% of time during winter five months. The system noise temperature was typically 1200 K (SSB) at 492 GHz and 500 K (DSB) at 345 GHz. The beam size was measured to be 2.'2 and 3.'1 at 492 and 345 GHz, respectively. We have conducted a large-scale survey of the CI (492 GHz) and CO (3 - 2: 345 GHz) emission from nearby molecular clouds with total area of 10 square degrees. We describe the telescope system and report the performance obtained in the 1998 winter.
NASDA and CRL are planning to develop a spaceborne SMILES, which is to be installed in the Exposed Facility (EF) on the JEM of the ISS. By observing gases such as ClO, HCl, NO, N2O, HO2 and BrO in the stratosphere, JEM/SMILES can trace the chemical reactions concerning the ozone depletion and climate change. Global distribution of those gases will be mapped with a height resolution of about 2 km. JEM/SMILES receives low-intensity signals from those gases with highly sensitive SIS (Superconductor-Insulator-Superconductor) mixers at 640 GHz, which are cooled to 4.2 K by a space-qualified mechanical cooler. The mission target is to demonstrate the effectiveness of the submillimeter-wave limb emission sounding and to establish space applicability of the low-noise SIS mixers and a mechanical 4-K cooler. JEM/SMILES is expected to be launched in 2003, and the experiments will last a year or more.
We have made a submillimeter-wave telescope for a Japanese sounding rocket, -520-17, which is dedicated for an observation of cold dust in Orion molecular cloud region. The submillimeter-wave telescope was launched on January 23, 1995. The telescope include an off-axis Gregorian telescope with aperture of 30cm, focal plane bolometer array, cryogenic cooling system down to 0.3K, and a star sensor using charge modulation device. A very low emissivity optical arrangement of less than 1% is achieved using pure aluminum mirror, off axis reflector and cold optics. Single moded conical feed horn is effectively coupled with bolometers with efficiency of more than 90%. The focal plane array consists of 12-element bolometers, six for 250 micrometers observation and six for 500 micrometers observation. NEPs of the bolometers are 5 X 10-17 W/(root)Hz which is read out by AC bridge read-out circuit. Total system gives sensitivities of about 10-12 W/cm2 (DOT) sr for diffuse objects or 2Jy for compact objects at 500 micrometers over 100deg2 region with a beam size of 10arcmin. This observation should give unique data on cold dust distribution, which is believed to dominate the dust mass distributional, over Orion Molecular Cloud region. Also discussed in the last section is a development of array detectors for future space mission in far-infrared and submillimeter-wave region.
Submillimeter-wave telescope on board S-520-17 was launched on January 23, 1995. The telescope is dedicated for observation of cold dust within Orion molecular cloud. In this paper, a brief description of the telescope system and review through the environmental test, preflight calibration, and flight performance is described. Also discussed in the last section is a development of array detectors for future space mission in far-infrared and submillimeter- wave.
We have made a submillimeter-wave telescope for a Japanese sounding rocket, S- 520-17, which is dedicated for an observation of cold dust in Orion molecular cloud region. The system is now under test for launch in Jan. 1995. The telescope include an off-axis Gregorian telescope with aperture of 30 cm, focal plane bolometer array, cryogenic cooling system down to 0.3 K, and a star sensor using charge modulation device. A very low emissivity optical arrangement of less than 1% is achieved using pure aluminum mirror, off axis reflector and cold optics. Single moded conical feed horn is effectively coupled with bolometers with efficiency of more than 90%. The focal plane array consists of 12-element bolometers, six for 250 micrometers observation and six for 500 micrometers observation. NEPs of the bolometers are 5 X 10-17W/√Hz which is read out by AC bridge read-out circuit. Total system gives sensitivities of about 10-12W/cm2 X sr for diffuse objects or 2 Jy for compact objects at 500 micrometers over 100 deg2 region with a beam sizes of 10 arcmin. This observation gives unique data on cold dust distribution, which is believed to dominate the dust mass distribution, over Orion Molecular Cloud region.
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