G008-0011
Development of novel ground-based microwave radiometer for earth science -field experiments of the wide-band receiver-

Thursday, 10 December 2020
Poster
Ryuichi Ichikawa1, Hideki Ujihara2, Shinsuke Satoh3, Yusaku Ohta4, Basara Miyahara5, Hiroshi Munekane6, Taketo Nagasaki7, Osamu Tajima8, Kentaro Araki9, Takuya Tajiri9, Hiroshi Takiguchi10, Takeshi Matsushima11, Nobuo Matsushima12, Tatsuya Momotani13 and Kenji Utsunomiya13, (1)NICT National Institute of Information and Communications Technology, Tokyo, Japan, (2)National Institute of Information and Communications Technology (NICT), Kashima Space Technology Center, Space-Time Standards Laboratory, Kashima, Japan, (3)National Institute of Information and Communications Technology, Koganei, Japan, (4)Tohoku University, Graduate School of Science, Sendai, Japan, (5)Geospatial Information Authority of Japan, Ibaraki, Japan, (6)Geospatial Information Agency of Japan, Tsukuba, Japan, (7)RIKEN, Wako, Japan, (8)Kyoto University, Kyto, Japan, (9)Meteorological Research Institute, Japan Meteorological Agency, Tsukuba, Japan, (10)JAXA Japan Aerospace Exploration Agency, Satellite Navigation Unit, Tsukuba, Japan, (11)Kyushu University, Shimabara, Japan, (12)National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan, (13)Japan Weather Association (JWA), Tokyo, Japan
Abstract:
We have started to develop a next-generation microwave radiometer to be used in millimeter-wave spectroscopy for the high-resolution and high-precision monitoring of water vapor behavior. The new radiometer will be suitable for not only space geodetic techniques such as VLBI and GNSS, but also field measurements such as monitoring volcanic activities and cumulonimbus cloud generation. The planned front-end system for our new microwave radiometer has a wide-bandwidth feed of 20–60 GHz for measuring two frequency bands of 20–30 GHz (H2O) and 50–60 GHz (O2). A signal from the wide-band feed is separated into two linear orthogonal polarized signals, one in the 20–30 GHz signal band and the other in the 50–60 GHz signal band, using an orthomode transducer (OMT). The wide-band feed, OMT, and LNA for each signal will be cooled at 77 K using a Stirling cryocooler to improve the signal-to-noise ratio. We assembled a room-temperature 20–30 GHz receiver without the cooling system in the middle of 2019 as a first step of our development. We implemented the new receiver into the 3.7 m dish at Okinawa Electromagnetic Technology Center, National Institute of Information and Communications Technology (NICT) and carried out first measurements using it for a validation test in October 2019. The quick-look data obtained by the new receiver showed good power signals for the expected receiving band of 18–28 GHz. We are now developing another receiver for a higher band of 50–60 GHz, and we are going to implement the second one into the new system by the end of this fiscal year. The development of a new front-end module including the OMT will be completed by the end of 2020. Although the experiment schedule for the validation of the new receiver is still uncertain owing to the COVID-19 pandemic, we are going to perform the experiments this fiscal year. We will compare the results of the field experiments with those of tropospheric delay measurements using the low-cost multi-GNSS receivers and the GNSS Earth Observation Network (GEONET) System of the Geospatial Information Authority of Japan (GSI).
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