Astronomical instrumentation

Abstract:

WEAVE is the next-generation spectroscopic facility for the William Herschel Telescope (WHT) 1,2. WEAVE offers multi-object (1000 fibres) and integral-field spectroscopy at two resolutions (R ~ 5000, 20000) over a 2-deg field of view at prime focus and will mainly provide follow up of ground-based (LOFAR) and space-based (GAIA) surveys. The Observatory Control System (OCS) is responsible for providing the software control and feedback framework through which WEAVE will be operated. This paper summarizes the design of the different OCS subsystems and the interfaces between them and other WEAVE components. In the remainder of this paper, Section 2 outlines the other WEAVE systems with which the OCS interacts, Section 3 describes the system architecture, Section 4 comments on system-architecture decisions, Section 5 describes the main components of the OCS, Section 6 outlines the life-cycle of an OCS Observing Block and, finally, Section 7 gives an overview of the OCS testing plan.

Abstract:

WEAVE is a new wide-field multi-object spectroscopy (MOS) facility proposed for the prime focus of the 4.2m William Herschel Telescope (WHT), situated on the island of La Palma, Canary Islands, Spain. To allow for the compensation of the effects of temperature-induced and gravity-induced image degradation, the WEAVE prime focus assembly will be translated along the telescope optical axis. The assembly comprises the prime focus corrector (PFC), a central mount for the corrector known as FTS[1], an instrument rotator and a twin-focal-plane fibre positioner. SENER, that manufactured and delivered the FTS, is also responsible for the final design, manufacturing, integration, alignment and testing of the PFC and its ancillary equipment. This manuscript describes the final design of the PFC along with the analyses and simulations performed and presents the procedures for the integration and alignment of the lenses in the corrector.

Abstract:

WEAVE is the new wide field multi-object and integral field survey facility for the prime focus of the 4.2 m William Herschel Telescope. It is located at the Observatorio Roque de los Muchachos, in La Palma, Canary Islands, Spain. WEAVE fiber-fed spectrograph offers two resolutions, R ~ 5000 and 20,000. It has a collimator mirror and two cameras optimized for the wavelength intervals of 366 - 959 nm and 579 - 959 nm, respectively. One of the responsibilities of INAOE within the WEAVE collaboration is the polishing of the collimator mirror, made of OHARA CLEARCERAM®- Z HS. The collimator has a diameter of 660 mm, a central thickness of 44.7 mm and a weight of 56.8 kg. The main specifications are: 2 fringes irregularity in a clear aperture of 624 mm diameter and a radius of curvature of 1224.65 mm +/- 0.15. In this work, we present the polishing process and final results for the collimator. In particular, we describe the tools developed for its manufacturing, the modifications carried out to the conventional polishing machine to support the glass. Additionally, the interferometric optical irregularity measurements are presented. The collimator polishing process is finished fulfilling all the optical specifications.

Abstract:

MOSAIC is a concept for a multi-object spectrograph for the Extremely Large Telescope (ELT). It is planned to cover the wavelength range from 460 nm to 1800 nm with two types of spectrographs, optimized for the visible and the near-infrared. There are two observing modes; multiplex mode with 200 sampling points and Integral Field Unit (IFU) mode with 10 fields. The instrument consists of 5 visible spectrographs and 5 near-infrared spectrographs. The ELT is far from diffraction limited in the visible wavelength range. Rather than developing a large and complex AO system, it was decided that the instrument will be seeing limited in the visible. Spot sizes are therefore about 2.8 mm in diameter in the ELT focal plane, and need to be sampled by multiple fibers with large core diameter. As a result, large optics is required to achieve the science requirements on spectral resolution, bandwidth and multiplex. We work in close collaboration with manufacturers to design an instrument that is feasible and meets the scientific requirements.