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Register a new userCurrent status and future plan of Osaka Prefecture University 1.85-m mm-submm telescope project
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We report the current status of the 1.85-m mm-submm telescope installed at the Nobeyama Radio Observatory (altitude 1400 m) and the future plan. The scientific goal is to reveal the physical/chemical properties of molecular clouds in the Galaxy by obtaining large-scale distributions of molecular gas with an angular resolution of several arcminutes. A semi-automatic observation system created mainly in Python on Linux-PCs enables effective operations. A large-scale CO $J=$2--1 survey of the molecular clouds (e.g., Orion-A/B, Cygnus-X/OB7, Taurus-California-Perseus complex, and Galactic Plane), and a pilot survey of emission lines from minor molecular species toward Orion clouds have been conducted so far. The telescope also is providing the opportunities for technical demonstrations of new devices and ideas. For example, the practical realizations of PLM (Path Length Modulator) and waveguide-based sideband separating filter, installation of the newly designed waveguide-based circular polarizer and OMT (Orthomode Transducer), and so on. As the next step, we are now planning to relocate the telescope to San Pedro de Atacama in Chile (altitude 2500 m), and are developing very wideband receiver covering 210--375 GHz (corresponding to Bands 6--7 of ALMA) and full-automatic observation system. The new telescope system will provide large-scale data in the spatial and frequency domain of molecular clouds of Galactic plane and Large/Small Magellanic Clouds at the southern hemisphere. The data will be precious for the comparison with those of extra-galactic ones that will be obtained with ALMA as the Bands 6/7 are the most efficient frequency bands for the surveys in extra-galaxies for ALMA.
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The corrugated horn is a high performance feed often used in radio telescopes. There has been a growing demand for wideband optics and corrugated horns in millimeter and submillimeter-wave receivers. It improves the observation efficiency and allows us to observe important emission lines such as CO in multiple excited states simultaneously. However, in the millimeter/submillimeter band, it has been challenging to create a conical corrugated horn with a fractional bandwidth of ~60% because the wavelength is very short, making it difficult to make narrow corrugations. In this study, we designed a conical corrugated horn with good return loss, low cross-polarization, and symmetric beam pattern in the 210-375GHz band (56% fractional bandwidth) by optimizing the dimensions of the corrugations. The corrugated horn was installed on the Osaka 1.85-m mm-submm telescope with the matched frequency-independent optics, and simultaneous observations of 12CO, 13CO, and C18O (J = 2-1, 3-2) were successfully made. In this paper, we describe the new design of the corrugated horn and report the performance evaluation results including the optics.
We have developed a wideband receiver system for simultaneous observations in CO lines of J = 2-1 and J = 3-2 transitions using the Osaka 1.85-m mm-submm telescope. As a frequency separation system, we developed multiplexers that connect three types of diplexers, each consisting of branch-line couplers and high-pass filters. The radio frequency (RF) signal is eventually distributed into four frequency bands, each of which is fed to a superconductor-insulator-superconductor (SIS) mixer. The RF signal from the horn is divided into two frequency bands by a wideband diplexer with a fractional bandwidth of 56%, and then each frequency band is further divided into two bands by each diplexer. The developed multiplexers were designed, fabricated, and characterized using a vector network analyzer. The measurement results showed good agreement with the simulation. The receiver noise temperature was measured by connecting the SIS-mixers, one of which has a wideband 4-21GHz intermediate frequency (IF) output. The receiver noise temperatures were measured to be ~70K in the 220GHz band, ~100K in the 230GHz band, 110-175K in the 330GHz band, and 150-250K in the 345GHz band. This receiver system has been installed on the 1.85-m telescope at the Nobeyama Radio Observatory. We succeeded in the simultaneous observations of six CO isotopologue lines with the transitions of J = 2-1 and J = 3-2 toward the Orion KL as well as the on-the-fly (OTF) mappings toward the Orion KL and W 51.
Since the ALMA North America Prototype Antenna was awarded to the Smithsonian Astrophysical Observatory (SAO), SAO and the Academia Sinica Institute of Astronomy & Astrophysics (ASIAA) are working jointly to relocate the antenna to Greenland. This paper shows the status of the antenna retrofit and the work carried out after the recommissioning and subsequent disassembly of the antenna at the VLA has taken place. The next coming months will see the start of the antenna reassembly at Thule Air Base. These activities are expected to last until the fall of 2017 when commissioning should take place. In parallel, design, fabrication and testing of the last components are taking place in Taiwan.
ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana) is a flagship project of the Italian Ministry of Education, University and Research. Within this framework, INAF is currently developing a wide field of view (9.6 degrees in diameter) end-to-end prototype of the CTA small-size telescope (SST), devoted to the investigation of the energy range from a fraction of TeV up to tens of TeVs, and scheduled to start data acquisition in 2014. For the first time, a dual-mirror Schwarzschild-Couder optical design will be adopted on a Cherenkov telescope, in order to obtain a compact optical configuration. A second challenging, but innovative technical solution consists of a modular focal surface camera based on Silicon photo-multipliers with a logical pixel size of 6.2mm x 6.2mm. Here we describe the current status of the project, the expected performance, and its possible evolution in terms of an SST mini-array. This CTA-SST precursor, composed of a few SSTs and developed in collaboration with CTA international partners, could not only peruse the technological solutions adopted by ASTRI, but also address a few scientific test cases that are discussed in detail.
We present the science case, reference design, and project plan for the Stage-4 ground-based cosmic microwave background experiment CMB-S4.
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