Multielement System Design in Astronomy and Radio Science

Kopilovich, L. E.; Sodin, L. G.

doi:10.1007/978-94-015-9751-7

Cited by 21 publications

(10 citation statements)

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“…Thus, by the method suggested in [14,15] and somewhat simplified in [3], when having an H set on the s t × grid, one can obtain the H set on the (2 ) (2 ) s t × grid. In this way the H sets on the 16 16 × grid can be built, and on their base the AAs with a large number (120 and 136) of elements having a low SLL synthesized, that becomes pressing in the development of modern radio telescopes [17].…”

Section: Resultsmentioning

confidence: 99%

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ARRAY ANTENNAS OF SIZE 8x8 BASED ON HADAMARD DIFFERENCE SETS

Kopilovich

2010

Radio Physics Radio Astronomy

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The problem of synthesizing the optimized equi-amplitude array antenna (AA) on the 8 8 × grid based on a Hadamard difference set is considered. By using newly found sets of this type on the 8 8 × grid the 28-and 36-element AAs having a low sidelobe level are obtained.A numerical experiment showed that by a small alteration of the structure of such a set, further reduction of the AA sidelobe radiation is possible.

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Section: Resultsmentioning

confidence: 99%

“…Further investigation of this issue in both linear and planar cases was described in monograph [3]. In particular, there it was shown that the basic DS class appropriate for the construction of planar aperiodic AAs is that of Hadamard difference sets (H sets [4]).…”

Section: Introductionmentioning

confidence: 99%

ARRAY ANTENNAS OF SIZE 8x8 BASED ON HADAMARD DIFFERENCE SETS

Kopilovich

2010

Radio Physics Radio Astronomy

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“…The array configuration, as well as the number and sizes of the telescopes, is a key issue in interferometric imaging (Kopilovich & Sodin 2001). The point spread function (PSF) is not a compact spot such as the Airy disk, and can have a structure that is apparently chaotic.…”

Section: Introductionmentioning

confidence: 99%

Strategies for the deconvolution of hypertelescope images

Aimé

Lantéri

Diet

et al. 2012

A&A

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Aims. We study the possibility of deconvolving hypertelescope images and propose a procedure that can be used provided that the densification factor is small enough to make the process reversible. Methods. We present the simulation of hypertelescope images for an array of cophased densified apertures. We distinguish between two types of aperture densification, one called FAD (full aperture densification) corresponding to Labeyrie's original technique, and the other FSD (full spectrum densification) corresponding to a densification factor twice as low. Images are compared to the Fizeau mode. A single image of the observed object is obtained in the hypertelescope modes, while in the Fizeau mode the response produces an ensemble of replicas of the object. Simulations are performed for noiseless images and in a photodetection regime. Assuming first that the point spread function (PSF) does not change much over the object extent, we use two classical techniques to deconvolve the images, namely the Richardson-Lucy and image space reconstruction algorithms. Results. Both algorithms fail to achieve satisfying results. We interpret this as meaning that it is inappropriate to deconvolve a relation that is not a convolution, even if the variation in the PSF is very small across the object extent. We propose instead the application of a redilution to the densified image prior to its deconvolution, i.e. to recover an image similar to the Fizeau observation. This inverse operation is possible only when the rate of densification is no more than in the FSD case. This being done, the deconvolution algorithms become efficient. The deconvolution brings together the replicas into a single high-quality image of the object. This is heuristically explained as an inpainting of the Fourier plane. This procedure makes it possible to obtain improved images while retaining the benefits of hypertelescopes for image acquisition consisting of detectors with a small number of pixels.

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“…Such NRCs were obtained in [4] with using combinatorial constructions -cyclic difference sets (see also [9]). However, it remains unclarified to what degree the element number of the NRC thus found is close to a maximum.…”

Section: Introductionmentioning

confidence: 99%