Celestial and atmospheric H2O detection by direct RF sampling IVTW in Bologna, Italy 09.40-10.00, October 11, 2017 Celestial and atmospheric H2O detection by direct RF sampling Noriyuki Kawaguchi Professor Emeritus National Astronomical Observatory of Japan Y. Kohno, T. Oyama, NAOJ T. Nagasaki, KEK, T. Maeda, JAXA K. Harada, Y. Chikahiro, Elecs

Contents Development of a high speed AD converter Direct RF detection of astronomical H2O maser emission Water Vapor Radiometer Direct detection of atmospheric H2O emission Volcano fume monitoring

The use of the InP HBT technology Development

30-GHz RF sampler, a trial unit A trial test unit of a high speed sampler. Clock Distributor 3-bit ADC 1:16 DEMUX Analog signal Input DC voltage generator

RF Direct sampled Digital Spectrum of 4-GHz BW The first successful result in 2007. 20.48GHz Fs=8.192GHz 24.576GHz Red Dots: RF Direct Digital Spectrum Green Dots: Analog Spectrum 20GHz 25GHz

Sampling Jitter 0.2-psec jitter Sampling jitter is a cause of fringe phase fluctuation. 0.2-psec jitter 2x10-13

Astronomical Application H2O maser in 22GHz Astronomical Application

W49N on Nobeyama 45m Observations were made on August 8, 2008 Digital RF direct sampler Digital Spectrum Conventional

Water Vapor Maser, W49N Observed by VERA, Honma(2004)

W49N on NRO 45m detected without frequency conversion Direct detection (20.480-24.576 GHz) Spectrum after frequency conversion LO=(16.85+3)-GHz signal converts a 22-GHz Signal to a 2.2-2.4GHz signal. The IF signal Is digitized at a speed of 8.192-GHz (over sampling), then Fourier transformed with 512K spectrum. A 20.480-24.576GHz (BW=4.096GHz) signal is directly digitized at a sampling rate of 8.192GHz, then Fourier trans- formed with 512K spectrum. The spectrum order is inverted.

GIGA Sampler for RF Sampling Now Commercial Available Presented by Harada Kenichi Elecs Industry Co.,Ltd., Japan

16Gsps × 3bit ENOB (Effective number of bits)

Water Vapor Radiometer For astronomy, Geodesy and Volcanology Water Vapor Radiometer

Absorption in Radio Astronomy The correction on tropospheric absorption is a key for good imaging and for deducing absolute brightness. 40K (https://www.cfa.harvard.edu/~spaine/am/)

Uncertainty in radio brightness

A variable star or sky fluctuation? -1.3dB ←1.2Jy (1.6Jy @l=30deg) ←1Jy -0.43dB Two weeks Forkman_Onsala_2003

VLBI vs WVR WVR delay VLBI delay 1 -1 2 Delay (mm) Time (seconds) 100 1 -1 2 Delay (mm) Time (seconds) 100 200 400 300 David A. Tahmoush and Alan E. E. Rogers, Correcting atmospheric path variations in millimeter wavelength very long baseline interferometry using a scanning water vapor spectrometer, Radio Science, Volume 35, Number 5, Pages 1241–1251, September–October 2000

KEK radiometer KEK: High Energy Particle Acceleration Research institution

Analog spectrum by KEK Noiser (rms)= 2.2K @Integ=30sec

Digital Spectrum 0.1 K ↔ 0.5 mm in EPL Error(rms)=0.106K @Integ=1sec 0.1 K ↔ 0.5 mm in EPL 0.01 K ↔ 0.05 mm in EPL by averaging 128 FFT points

Time profile at the spectrum peak F=22.7 GHz (FFT point=56) Rms=0.13 K 0.13×4.5 128× 3× 10 11 =𝟏.𝟕× 𝟏𝟎 −𝟏𝟑 DSN WVR: 5x10-12 SHAO WVR: 5x10-12 UoB WVR: 1.7x10-12 HALCA: 1x10-12 UoB Corr WVR: 1x10-12 DSN AWVR: 6x10-13 Australia WVR: 4x10-13 H. Maser: 1x10-13 0.13 K ↔ 0.6 mm in EPL The precision is the best in the world!

Water vapor monitoring in a volcano fume volcanology

Disaster in Ontake in 2014, Japan 56 confirmed dead and seven still missing After deadly eruption, Japan ponders how to improve predictions, By Dennis Normile Oct. 17, 2014, Science News

Gas Composition Decrease in the water vapor, volcanologists says that it is a sign of eruption. Burton_2007

H2O monitoring of a volcano fume Bryan_2016 1.5-K increase 1.5K in Tb ↔ 6.8 mm in EPL↔1 mm in PWV ↔ 1 kg/m2 in column density

Summaries A high speed RF sampling system was developed. Good agreement between digital and analog spectra was obtained. W49N spectra were successfully detected with RF sampling A new digital WVR is now being developed. The digital spectrum noise is estimated to be from 0.1 to 0.3K at integration time of 1 second. The noise is estimated to be 0.13K. It shows the best stability in the world. New application to Volcanology

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Higher Order Nyquist Sampling 6 12 18 24 30 8 16 28 ① ② ③ Waveguide(WRJ240) Pass Band 26 Freq.（GHz） RF Spectrum ＃１ ＃２ 20 8Gsps Digital Spectrum 4