SOXS (Son Of X-Shooter) will be a unique spectroscopic facility for the ESO-NTT 3.5-m telescope in La Silla (Chile), able to cover the optical/NIR band (350-1750 nm). The design foresees a high-efficiency spectrograph with a resolutionslit product of ~4,500, capable of simultaneously observing the complete spectral range 350 - 1750 nm with a good sensitivity, with light imaging capabilities in the visible band. This paper outlines the status of the project.
The communication presents an innovative method for the diagnosis of reflector antennas in radio astronomical applications. The approach is based on the optimization of the number and the distribution of the far field sampling points exploited to retrieve the antenna status in terms of feed misalignments, this to drastically reduce the time length of the measurement process and minimize the effects of variable environmental conditions and simplifying the tracking process of the source. The feed misplacement is modeled in terms of an aberration function of the aperture field. The relationship between the unknowns and the far field pattern samples is linearized thanks to a Principal Component Analysis. The number and the position of the field samples are then determined by optimizing the Singular Values behaviour of the relevant operator.
The paper presents an innovative method for the diagnosis of reflector antennas in radio astronomical applications,
which optimizes the number and the location of the far field sampling points exploited to retrieve the antenna status in
terms of feed misalignments. In this way the measurement time length process is drastically reduced to minimize the
effects of the time variations of the measurement setup, as well as the idle time forced by the maintenance activity. The
effects of the feed misalignment are modeled in terms of an aberration function, properly expanded on a set of basis
functions in order to preserve the linear relationship between the unknown parameters defining the antenna status and the
far field pattern, assumed measured in amplitude and phase. Thanks to the optimization of the Singular Values behavior
of the relevant linear operator, in its discrete form, the number and the position of the samples is found. The numerical
analysis shows the effectiveness of the method in the simple case of a phase aperture affected by tilt only, even if the
approach can be extended also to higher order aberrations. The performances are estimated with a comparison with a
standard approach, based on the acquisition of the far field pattern by means of a uniform Cartesian grid defined
according the Nyquist criterion and requiring a number of field samples significantly larger.