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| ＞ALMA-J Site Testing Archive |
Last update
2005-01-24
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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