Prof Gavin Dalton

Abstract:

MOSAIC is a wide-field spectrograph, combining multiple-object spectroscopy and integral field units, to cover the ELT focal plane with a field-of-view of 7.8 arcmin from the blue to the near-infrared, 390 to 1800nm. In the current Phase B design, AO is GLAO supported by four LGS in a fixed asterism and with multiple NGS. Although the GLAO correction is modest compared to other ELT instrumentation, the use of the integrated M4/M5 correction elements and the existing LGS allows for an efficient design which is outlined. MOSAIC GLAO will use the ELT PFS guide-probes to compensate for high- frequency tip/tilt errors, greatly relaxing the requirements on the instrumental NGS sensors. The Phase A architecture used the same pick-off mirrors as the IFU instruments to feed the NGS-WFS from anywhere in the focal plane, which was mandatory for the proposed MOAO design. The reduced performance requirements at Phase B allows us to take advantage, instead, of the four 2 arcmin diameter field-of-view through the LGS cutouts, arranged in a square pattern at an off-axis distance of 3.75 arcmin. In each LGS cutout, a wide-field-imager is implemented–alongside one LGS WFS–to acquire multiple NGS that supports both slow tip/tilt measurements, isolating instrument-Nasmyth flexure, solving for the astrometric distortion expected from errors in the ELT optical path, and supporting the alignment of MOS apertures with the field. The latter is a key requirement for MOSAIC, leading to 40mas accuracy in MOS aperture positioning and 40mas rotation displacement at the edge of the scientific field.

Abstract:

MOSAIC is an instrument for the Extremely Large Telescope (ELT). The instrument has started phase B, and apart from technical and financial requirements, MOSAIC has the additional requirement to investigate and minimise its environmental impact. The first step is to estimate the carbon footprint (and other effects) in a ‘Life Cycle Analysis’, for the instrument development up to Provisional Acceptance in Chile. This paper presents a preliminary analysis, aimed at identifying potential contributors to environmental impact. Investigated contributors are: materials, Full-Time-Equivalents, travel, and transport of the instrument. Not yet investigated (due to lack of information or certainty) are: electronics, test facilities and prototyping. Uncertainty in input data and conversion factors leads to error bars of a factor 2 or larger. Therefore, the outcome of the analysis can be used for internal comparison of contributors only, and it should not be used for comparison to other instruments or disciplines.

Abstract:

MOSAIC is the Muti-Object Spectrograph for the 39m ESO Extremely Large Telescope. The instrument development has recently been reorganized in different channels to be implemented progressively. The Laboratoire d’Astrophysique de Marseille (LAM) is in charge of the instrument “Assembly, Integration, Test and Verification (AIT/V)” phases. AITV for AO instruments, in laboratory as at the telescope, always represent numerous technical challenges. We already started the preparation and planning for the instrument level AIT activities, from identification of needs, challenges, risks, to defining the optimal AIT strategy.

In this paper, we present the state of this study, discuss a new approach with distributed AIT activities and controlled remotely over different sites. We describe AIT/V scenarios with phased implementation, starting with the Front-End and Visible channels AIT phases. We also show our capacity, experience (several MOS instruments, ELT HARMONI) and expertise to lead the instrument MOSAIC AIT/V activities both in Europe and at the telescope in Chile.

Abstract:

MOSAIC is the Multi-Object Spectrograph (MOS) for the 39m Extremely Large Telescope (ELT) of the European Southern Observatory (ESO), with unique capabilities in terms of multiplex, wavelength coverage and spectral resolution. It is a versatile multi-object spectrograph working in both the Visible and NIR domains, designed to cover the largest possible area (∼40 arcmin2) on the focal plane, and optimized to achieve the best possible signal-to-noise ratio on the faintest sources, from stars in our Galaxy to galaxies at the epoch of the reionization. In this paper we describe the main characteristics of the instrument, including its expected performance in the different observing modes. The status of the project will be briefly presented, together with the positioning of the instrument in the landscape of the ELT instrumentation. We also review the main expected scientific contributions of MOSAIC, focusing on the synergies between this instrument and other major ground-based and space facilities.