We report the current status of the NASCO (NAnten2 Super CO survey as legacy) project which aims to provide all-sky CO data cube of southern hemisphere using the NANTEN2 4-m submillimeter telescope installed at the Atacama Desert through developing a new multi-beam receiver and a new telescope control system. The receiver consists of 5 beams. The four beams, located at the four corners of a square with the beam separation of 720′′, are installed with a 100 GHz band SIS receiver having 2-polarization sideband-separation filter. The other beam, located at the optical axis, is installed with a 200 GHz band SIS receiver having 2-polarization sideband-separation filter. The cooled component is modularized for each beam, and cooled mirrors are used. The IF bandwidths are 8 and 4 GHz for 100 and 200 GHz bands, respectively. Using XFFTS spectrometers with a bandwidth of 2 GHz, the lines of 12CO, 13CO, and C18O of J=1−0 or J=2−1 can be observed simultaneously for each beam. The control system is reconstructed on the ROS architecture, which is an open source framework for robot control, to enable a flexible observation mode and to handle a large amount of data. The framework is commonly used and maintained in a robotic field, and thereby reliability, flexibility, expandability, and efficiency in development are improved as compared with the system previously used. The receiver and control system are installed on the NANTEN2 telescope in December 2019, and its commissioning and science verification are on-going. We are planning to start science operation in early 2021.
In the southern South America, various types of aerosols have been observed including biomass burning aerosols from the Amazon region, flying ashes from the volcanic eruptions coming from the Andean Volcanic Belt, mineral dust from the Patagonian Desert, and air pollution aerosols from urban areas. To monitor such aerosols continuously, we developed a lidar observation network in Argentina and Chile. Eight lidars were installed in Argentina and one in Punta Arenas, Chile. Backscattering signals are measured at three wavelengths: 355, 532, and 1064 nm. Eight of those instruments are measuring depolarization ratio at 355 and 532 nm to detect non-spherical aerosols. In addition, four lidars are equipped Ramans channels and two high-spectral-resolution channels to measure backscattering and extinction coefficients quantitatively. Lidar operation, data analysis, and products release are implemented within the South American Environmental Risk Management Network (SAVER-Net) system, which was developed by a trinational project among Japan, Argentina, and Chile. Using lidar data, hazard information on the aerosol type and extinction coefficient at low altitude is provided for public in a near real time. In addition, plume height and qualitatively concentration for volcanic ashes are estimated. The information on volcanic ashes may be effectively used for advising aircraft landing and departing when volcanic eruptions occurs.
Continuous monitoring of aerosol profiles using lidar is helpful for a quasi-real-time indication of aerosol concentration. For instance, volcanic ash concentration and its height distribution are essential information for plane flights. Depolarization ratio and multi-wavelength measurements are useful for characterizing aerosol types such as volcanic ash, smoke, dust, sea-salt, and air pollution aerosols. High spectral resolution lidar (HSRL) and Raman scattering lidar can contribute to such aerosol characterization significantly since extinction coefficients can be measured independently from backscattering coefficients. In particular, HSRL can measure aerosol extinction during daytime and nighttime with a high sensitivity. We developed an HSRL with the iodine filter method for continuous observation of aerosols at 532nm in the northern region of Argentina in the framework of the South American Environmental Atmospheric Risk Management Network (SAVER.Net)/SATREPS project. The laser wavelength of the HSRL was controlled by a feedback system to tune the laser wavelength to the center of an iodine absorption line. The stability of the laser wavelength with the system satisfied the requirement showing very small systematic errors in the retrieval of extinction and backscatter.
Atmospheric monitoring stations are being developed in Argentina. The most important targets are volcanic ashes, desert aerosols in particular Patagonian dust and biomass burning aerosols. Six stations deployed in the Patagonian Region and Buenos Aires have lidar systems, sun photometers integrated to the AERONET/NASA monitoring network, in situ optical particle analyzers, four solar radiation sensors (pyranometer, UVA, UVB and GUV), and meteorological equipment. The stations are in the main international airports of the Regions (San Carlos de Bariloche, Comodoro Rivadavia, Neuquén, Rio Gallegos) and in Buenos Aires (Aeroparque Jorge Newbery and at CEILAP/CITEDEF). CEILAP and the National Institute of Environmental Studies (NIES) at Tsukuba, Japan developed the first iodine cell-based high spectral resolution lidar (HSRL) in Argentina to add in the lidar network. We upgraded the standard CEILAP multi-wavelength Raman lidar adding the laser frequency tuning system and the 532 iodine-filtered channel at the reception to built the HSRL. HSRL will provide daytime and nighttime direct observation of the aerosol and cloud optical properties (backscatter and extinction) without the pre-assumption of the lidar ratio. This work shows the design and construction of the first Argentinean HSRL. We also show the first lidar observations done in the country with this kind of lidar.
With the aim of contribution to the study of atmospheric ozone layer, a new sensitive radiometer for atmospheric minor
constituents has been installed in the Observatorio Atmosférico de la Patagonia Austral, División LIDAR, CEILAP
(CITEDEF-CONICET), in October 2010. This observatory is established in the city of Rio Gallegos (51° 36' S, 69° 19'
W), Argentina, close to the spring ozone hole. The millimeter wave radiometer was developed in STEL (Solar
Terrestrial Environment Laboratory), Nagoya University, Japan. This passive remote sensing instrument is able to
measure the ozone (O3) amount in the high stratosphere and mesosphere continuously and automatically with a high time
resolution. The millimeter wave radiometer ozone profiles will be supplemented with the ozone profiles obtained from
the DIAL system existent in the observatory.
The millimeter wave radiometer is based on the spectral signal detection from the atmosphere due to the molecular
rotational transition of molecules under study. The operation is based on a superheterodyne system which uses a
Superconductor-Insulator-Superconductor (SIS) mixer receiver operating at 203.6GHz. The SIS mixer junction consists
of a sandwich structure of Nb/AlOx/Nb, and is cooled to 4.2K with a closed cycle He-gas refrigerator. Two additional
heterodyne-mixed stages are realized with the aim to shift the measured spectral line until a frequency around of 500
MHz. A FFT (Fast Fourier Transform) spectrometer system is used as a back end.
The aims of this work are to show the potential of the millimeter wave radiometer installed in the subpolar latitudes close
to the polar ozone hole and to present the preliminary result of the first measurements.
KEYWORDS: Receivers, Waveguides, Beam splitters, Extremely high frequency, Signal detection, Signal attenuation, Oscillators, Radio telescopes, Heterodyning, Astronomical telescopes
In millimeter and submillimeter wave band, radio telescopes' observing efficiency and weak signal detecting capability have been greatly raised in the past tens of years, due to the application of the SIS mixers as their receiver front-ends. However general local power injection methods for a heterodyne receiver usually result in additional insertion loss which degrades sensitivity of SIS receivers. Based on the extremely small local power requirements of SIS quantum mixing, we developed a novel LO path built-in SIS mixer, in which an additional waveguide was built for LO power injection. Without any of traditional external LO diplexers (e.g., crossguide- couplers or beamsplitters), LO power is provided to SIS junctions through the LO waveguide and the junction chip which connects both LO- and signal waveguides. There is no RF signal lost due to coupling LO power since LO- and RF signal take different paths before arriving at junctions, resulting in a compact, stable and lower loss SIS receiver system. Experiments at 110- and 230 GHz bands show that there is no any problem to couple sufficient pumping power to SIS junctions from general LO sources for present LPB mixer, and the receiver sensitivities have a further improvement of about 10 K compared to our previous beamsplitter LO power coupling receiver system. We expect this LPB SIS mixer can be also applied into submillimeter wave band.
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