Surface adjustment of the IRAM 30 m radio telescope

Morris, David J.; Bremer, M.; Butin, G.; Carter, M.; Greve, A.; Lamb, James W.; Lazareff, B.; Pérez, José Antonio López; Mattiocco, F.; Peñalver, J.; Thum, C.

doi:10.1049/iet-map:20080044

Cited by 20 publications

(16 citation statements)

References 9 publications

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“…In relation with the preceding solution to C e as shown in equation (11), the term (cos E e cos E o ) in equation (10) is approximated by 1 and thus ignored, compared with the original equation (7). However, by preserving the cosine, one may obtain a more accurate version of equation (10):…”

Section: Further Improvementmentioning

confidence: 99%

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Surface Shape Detection with a Single Far-Field Intensity by Combined Amplitude and Phase Retrieval

Jin

Huang

et al. 2019

International Journal of Antennas and Propagation

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The efficiency of a reflector antenna highly depends on its surface shape. In order to ensure a good convergence, the conventional phase retrieval based shape detection schemes require that several far-field intensities be scanned, focused, or defocused. For large reflector antennas, the scanning process is time consuming. This paper proposes a new shape detection method that requires only single far-field intensity. Unlike existing shape detection methods, it retrieves both the amplitude and the phase, based on the fact that a deformed shape causes change not only in the aperture phase but also in the aperture amplitude. Through even-odd decomposition analysis, it is found that in the case of small and smooth deformation, “odd-phase” and “even-amplitude” can be directly recovered from one focused far-field intensity. This leads to the recovery of both the odd and the even parts of the antenna surface shape simultaneously. By combining amplitude retrieval and phase retrieval, this work achieves for the first time the shape detection with only one scan.

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Section: Further Improvementmentioning

confidence: 99%

“…ese efforts lead to a more accurate phase recovery. However, most of them still require several far-field scans, usually the focused, the positive, and negative defocused [6,7]. For huge reflector antennas, multiple-scan is time consuming and laborious.…”

Section: Introductionmentioning

confidence: 99%

Surface Shape Detection with a Single Far-Field Intensity by Combined Amplitude and Phase Retrieval

Jin

Huang

et al. 2019

International Journal of Antennas and Propagation

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“…High efficiency at λ 850 μm requires <20 μm rms surface error (for >90% Strehl ratio) [11], which can be achieved with inexpensive machined panels [12]. The proposed design fills a gap in capability because existing large, single-dish telescopes are on poor sites and have low efficiency at short millimeter wavelengths [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Inexpensive mount for a large millimeter-wavelength telescope

Padin¹

2014

Appl. Opt.

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A telescope mount with a single-point force support at the center of gravity of the primary mirror is proposed in order to eliminate much of the structure and cost of a large, millimeter-wavelength telescope. The single-point support gives repeatable thermal and gravitational deformation, so the surface of the primary can be controlled based on lookup tables for elevation and temperature. The new design is most appropriate for a survey telescope because locating the support above the vertex of the primary limits the range of motion of the mount to about 1 rad. A 30 m diameter, λ 850 μm telescope with the proposed mount is a factor of 4 lighter than a design with a conventional elevation-over-azimuth mount, and roughly half the cost.

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“…In conventional (coherent) holography, the amplitude and phase of the beam pattern are measured, and the aperture function is recovered by Fourier inversion [1,2]. The phase reference for the measurement is provided by an auxiliary antenna, which might be an interferometer element, or a small horn mounted on the main telescope [3][4][5]. Conventional holography is sensitive, so it is widely used for accurate surface measurements with high spatial resolution.…”

Section: Introductionmentioning

confidence: 99%

“…Measurements that require high accuracy are usually made at millimeter wavelengths. Satellite beacons at ∼40 GHz have been used to measure the IRAM 30 m and Heinrich Hertz Telescopes [3,12], but the satellites have failed or drifted out of orbit. A transmitter on a drone is another option, but stability of the transmitter position is a problem.…”

Section: Introductionmentioning

confidence: 99%

Rayleigh beacon for measuring the surface profile of a radio telescope

Padin¹

2014

Appl. Opt.

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Millimeter-wavelength Rayleigh scattering from water droplets in a cloud is proposed as a means of generating a bright beacon for measuring the surface profile of a radio telescope. A λ 3 mm transmitter, with an output power of a few watts, illuminating a stratiform cloud, can generate a beacon with the same flux as Mars in 10 GHz bandwidth, but the beacon has a narrow line width, so it is extremely bright. The key advantage of the beacon is that it can be used at any time, and positioned anywhere in the sky, as long as there are clouds.

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Surface adjustment of the IRAM 30 m radio telescope

Cited by 20 publications

References 9 publications

Surface Shape Detection with a Single Far-Field Intensity by Combined Amplitude and Phase Retrieval

Surface Shape Detection with a Single Far-Field Intensity by Combined Amplitude and Phase Retrieval

Inexpensive mount for a large millimeter-wavelength telescope

Rayleigh beacon for measuring the surface profile of a radio telescope

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