Basic Experiments of the Multi-Frequency Lens Film Developed towards a Gigantic Radio Telescope

2004 Fiscal Year Final Research Report Summary

• Project/Area Number: 15340067
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Astronomy
• Research Institution: National Astronomical Observatory
• Principal Investigator: CHIKADA Yoshihiro National Astronomical Observatory, Div.Radio Astronomy, Professor, 電波研究部, 教授 (30126122)
• Co-Investigator(Kenkyū-buntansha): KAWAGUCHI Noriyuki National Astronomical Observatory, Div.Radio Astronomy, Professor, 電波研究部, 教授 (90214618) ; KASUGA Takashi Hosei Univ., Fac.Eng., Professor, 工学部, 教授 (70126027) ; NAKAHIRA Katsuko Nagaoka University of Technology, e-Learning Center, eラーニング実践センター, 助手 (80339621)
• Project Period (FY): 2003 – 2004
• Keywords: Radio Astronomy / Radio Telescope / Antenna / Lens / Satellite Antenna

Research Abstract

Aperture area of a radio telescope is approaching its limit. It is caused by the fact that, for a telescope whose diameter exceeds 104 of observing wavelength, it is difficult to maintain its surface error less than 1/10 of the wavelength, under actual conditions of gravity, winds, non-uniformity of temperature distributions, etc. Considering the sensitivity of the receiver front-ends are now approaching its theoretical limits, it appears for the radio astronomy of the 21st century to meet the dead-ends without realizing much larger collecting area.
A room mirror of a car swings as the car roll, and the scenery through it will suffer blur. On the other hand, eye glasses may jump on your nose without serious blur. That is, compared to reflective mirrors, the transparent lenses may easily be held maintaining their line of sight. In the latter case, only the line between the focus and the center of the lens should be kept towards the celestial object, and the tilt of the lens is allowed to a certain amount. In other words, from the view point of the symmetry, the lens could be folded or be in arbitrary shape if the "thickness" be kept. This is the advantage of lenses.
To provide a good focus for wide bandwidth, our study showed that the shape of the thin film lens should be a part of a spherical shell and the focus point should be at the center of sphere. The known problem is the position of the focus varies with the frequency. This problem might be lessened with the use of reducing optics.
Basic data were collected and studied toward multi-frequency lens antenna.