492GHz電波放射計
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492 GHz Radiometer

A portable 492 GHz radiometer fabricated at the Depertment of Physics (Yamamoto group) of the University of Tokyo was used to measure the correlation between the atmospheric transparency at 492 GHz with that at 220 GHz. The 492 GHz radiometer was temporally operated with the NRO 220 GHz radiometer at Pampa la Bola (4800 m a.s.l.) from 1997 June 28 to July 1 and at Rio Frio (4100 m a.s.l.) from 1997 July 2 to 4. Shown on the left-hand side of the photograph is a 492 GHz telescope, which succeeded to the 492 GHz radiometer, developped by the same group. One of the NRO 220 GHz radiometer is seen on the right-hand side.

Specifications

Primary mirror	Optics	Offset parabola
	Diameter	50 mm
	Beam width	1 deg (FWHM) at 492 GHz
Frontend	Feed	Conical horn
	Mixer	Uncooled GaAs Shottky diode harmonic mixer
	Harmonics	Second
	System temperature	12000 K (DSB)
LO	Frequency	82.25 x 3 GHz
	Oscillator	Gunn diode
IF	Frequency	1.5 GHz
	Bandwidth	500 MHz
Scan	Scan angle	-90 - +82.8 deg
	Stepping angle	0.72 deg
	Scan time	120 s
	Integration time	0.2 s
System	Total weight	25 kg
	Power consumption	30 W

Technical Description

Figure 1: Block diagram

References

• Hirota, T., Yamamoto, S., Sekimoto, Y., Kohno, K., Nakai, N., & Kawabe, R. 1998, ``Measurements of the 492 GHz atmospheric opacity at Pampa la Bola,'' PASJ, 50, 155; NROR 455

Data

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