We present an update on the overall construction progress of the WEAVE next-generation spectroscopy facility for the William Herschel Telescope (WHT), now that all the major fabrication contracts are in place. We also present a summary of the current planning behind the 5-year initial phase of survey operations, and some detailed end-to-end science simulations that have been effected to evaluate the final on-sky performance after data processing. WEAVE will provide optical ground-based follow up of ground-based (LOFAR) and space-based (Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2-degree prime focus field of view at the WHT, with a buffered pick-and-place positioner system hosting 1000 multi-object (MOS) fibres, 20 integral field units, or a single large IFU for each observation. The fibres are fed to a single (dual-beam) spectrograph, with total of 16k spectral pixels, located within the WHT GHRIL enclosure on the telescope Nasmyth platform, supporting observations at R~5000 over the full 370-1000nm wavelength range in a single exposure, or a high resolution mode with limited coverage in each arm at R~20000. The project has experienced some delays in procurement and now has first light expected for the middle of 2019.

On June 25th 2017, the new intermediate-resolution optical IFU and MOS of the 10.4-m GTC had its first light. As part of the tests carried out to verify the performance of the instrument in its two modes (IFU and MOS) and 18 spectral setups (identical number of VPHs with resolutions R=6000-20000 from 0.36 to 1 micron) a number of astronomical objects were observed. These observations show that MEGARA@GTC is called to fill a niche of high-throughput, intermediateresolution IFU and MOS observations of extremely-faint narrow-lined objects. Lyman-α absorbers, star-forming dwarfs or even weak absorptions in stellar spectra in our Galaxy or in the Local Group can now be explored to a new level. Thus, the versatility of MEGARA in terms of observing modes and spectral resolution and coverage will allow GTC to go beyond current observational limits in either depth or precision for all these objects. The results to be presented in this talk clearly demonstrate the potential of MEGARA in this regard.

A method for the evaluation of the shape of fast conical surfaces based on the null-screen method is presented. The proposed method is based on randomized algorithms, where instead of integration as is usually performed, the shape of the surface is recovered in a direct and random way. This is done by proposing a new test surface; the surface parameters are randomly generated and the calculated null-screen is compared against the originally designed one. The coefficients that generate the null-screen closest to the reference null-screen are taken as the final values that describe the surface under test. The algorithm validation was done in the theoretical and experimental way. For the theoretical way, a convex parabolic surface with 21.36 mm radius of curvature and f/0.178 was simulated and analyzed; in the experimental way, a convex spherical surface f/0.33 and a concave ellipsoidal mirror f/0.2381 were evaluated. The results obtained with our algorithm in the evaluation of the ellipsoidal surface were compared against the results obtained with traditional methods. We found that the radius of curvature, conic constant, and the decentering coefficients that were used to generate each surface were retrieved in a good manner with our algorithm. The results show that these parameters can be recovered with a percent error smaller than 1% in the case of simulations, and smaller than 2% in the two experimental cases.

We present the validation for Ronchigram recovery with the random aberrations coefficients (ReRRCA) algorithm. This algorithm was proposed to obtain the wavefront aberrations of synthetic Ronchigrams, using only one Ronchigram without the need for polynomial fits or trapezoidal integrations. The validation is performed by simulating different types of Ronchigrams for on-axis and off-axis surfaces. In order to validate the proposed analysis, the polynomial aberration coefficients that were used to generate the simulated Ronchigrams were retrieved. Therefore, it was verified that the coefficients correspond to the retrieved ones by the algorithm. The results show that the ReRRCA algorithm retrieves the aberration coefficients from the analyzed Ronchigram with a maximum error of 9%.

Substructured Ronchi gratings are used to sharpen and increase the number of fringes in Ronchigrams, thereby increasing their spatial resolution and allowing greater accuracy in the evaluation of a surface under test. This work presents a simple method for generating substructured Ronchi gratings and for calculating the intensity pattern produced by this type of grating. For this, we propose the generation of this kind of grating from the linear combination of classical gratings; the pattern of irradiance produced by these Ronchi gratings will be a linear combination of the intensity patterns produced by each combined classical grating. A comparison between theoretical and experimental Ronchigrams was obtained by analyzing a parabolic mirror.

Aluminum thin films were deposited on a 3D prototype employing the direct current magnetron sputtering technique to fabricate a lightweight 3D first surface mirror. Before the aluminizing, the surface of the prototypes was evaluated with interferometry and atomic force microscope (AFM). The thin films were characterized using profilometry, UV-Vis spectroscopy, x-ray diffraction, AFM, x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. High adherence and homogeneous deposition of the aluminum’s thin films were achieved. In addition, the purity of the material was confirmed by XPS analysis.