The Mirror-slicer Array for Astronomical Transients (MAAT) is an IFU now being manufactured for the OSIRIS spectrograph on the 10.4-m GRANTECAN (GTC) telescope at La Palma. It is based on the Advanced Image Slicer (AIS) concept as are MUSE and KMOS on the VLT (among many others). Very significant changes to the design had to be made due in part to cost limitations but mostly weight limitations. We present the final design, its expected performances, and the process to get there, in particular the difficulties encountered to avoid variable vignetting in the spectrograph due to the telescope derotator and the primary hexagonal shape. This especially includes modifications of the pupil shape and a new method of extreme optimization of AIS that has been 25 years in the making and that push the Zemax software to its extreme limit. MAAT will take advantage of the OSIRIS mask cartridge for multi-object spectroscopy. The IFU will be in a box that will take the place of a few masks. The field is 10" x 7" with 23 slices 0.305" wide giving a spaxel size of 0.254" x 0.305". The wavelength range is 360 nm to 1000 nm. The spectral resolution will be 1.6 times larger than with a standard slit of 0.6" because of the smaller size of the slices. The eleven gratings will deliver R = 600 to 4100. In an effort to maximize the resolution of a spectrograph designed for a slit twice the width of the slices, we measured the wavefront of the spectrograph by using 2 out-of-focus masks with pinholes along the slit and compared it to the as-designed wavefront. The goal was to modify the IFU pupil mirrors to partly cancel the aberrations in the spectrograph. This showed a residual wavefront variable over the detector due to tolerances, even negligible in some parts; wavefront almost only made of focus, coma, astigmatism and spherical aberration.
The new Integral Field Unit (IFU) for the OSIRIS spectrograph on the 10.4-m Gran Telescopio CANARIAS (GTC), Mirror-slicer Array for Astronomical Transients (MAAT), will see its first light in Autumn 2024. The field is 10" x 7" with 23 slices 0.305" wide, resulting in a spaxel size of 0.254" x 0.305". The wavelength range is 360 nm to 1000 nm. The spectral resolution will be approximately 1.6 times larger than with a standard slit of 0.6" due to the smaller size of the slices. All eleven Volume Phase Holographic Gratings (VPHs) and grisms will be available to provide broad spectral coverage with low to intermediate resolution (R=600 to 4100). The small space envelope, the maximum weight of the mask holder, and the curvature and tilt of the slit created additional design challenges. We will present the relevant aspects of the construction of the MAAT IFU optical bench, mechanical support, and the upgrade of the OSIRIS Mask Charger necessary to host MAAT.
The Mirror-slicer Array for Astronomical Transients (MAAT) is a new IFU for the OSIRIS spectrograph on the 10.4-m Gran Telescopio CANARIAS (GTC) at La Palma, spectrograph that has been recently upgraded with a new detector and moved to the Cassegrain focus. Funding has been secured to build MAAT. We present the nearly final design, its expected performances, the different options that were studied, and an analysis of the spectrograph aberrations. MAAT will take advantage of the OSIRIS mask cartridge for multi-object spectroscopy. The IFU will be in a box that will take the place of a few masks. It is based on the Advanced Image Slicer (AIS) concept as are MUSE and KMOS on the VLT (among many others). The field is 10" x 7" with 23 slices 0.305" wide giving a spaxel size of 0.254" x 0.305". The wavelength range is 360 nm to 1000 nm. The small space envelope, the maximum weight of the mask holder, and the curvature and tilt of the slit created additional design challenges. The spectral resolution will be about 1.6 times larger than with a standard slit of 0.6" because of the smaller size of the slices. All the eleven VPHs and grisms will be available to provide a broad spectral coverage with low to intermediate resolution (R=600 to 4100). To maximize the resolution of a spectrograph designed for a slit twice the width of the slices, we are in the process of measuring the wavefront of the spectrograph aberrations by using 2 out-of-focus masks with pinholes along the slit. We will then correct some of these aberrations with MAAT.
KEYWORDS: Instrument modeling, Sensors, Systems modeling, Control systems, Data modeling, Algorithm development, Software development, Safety, Cameras, Data acquisition
Model-based systems engineering has as one of its central pillars the single source of truth that is usually a CAD model, or a model defined using a language such as SysML. However, having a single point of truth is not incompatible with using multiple modeling languages. A simple DSL like PORIS allows us to make instrument sketches much more concise and understandable than if we made them in SysML. By providing this language with transformers, we can automatically and instantly generate configuration panels, diagrams and documentation that allow the scientific team of the instrument to create more quickly and formally the configuration and functional specifications of the instrument. Engineers can also create a high percentage of the instrument software, for instance, the ones related to configuration, monitoring, diagnostics or safety. In this article we will show how, starting from a simple model in a spreadsheet, we will end integrating its software in the GTC control system.
OSIRIS (Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy) Multi-Object Spectroscopy (MOS) observing mode is available to the science community of the GTC (Gran Telescopio Canarias) from early 2014. The MOS production line allows the researchers to specify a MOS observation in a self-contained way by using a software tool, in order to bridge the gap between science aims and the multiplexed spectroscopic data gathering at the telescope. It gives the researcher the guarantee that the observation will perform as expected, thanks to the computer vision based quality control checks of the masks produced.
This article describes the architecture of the production line of MOS observations, its activities, actors, and subsystems, and how all of them mesh so that the production line works efficiently and effectively, in an automatized way, using a model-centric approach where the observation design acts as the single source of truth for the entire organization.
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