A-DOT (Active Deployable Optical Telescope) is a payload prototype of a 6U deployable telescope operating in the visible from 400 to 800 nm with an aperture diameter of 300 mm. It aims to deliver diffraction-limited performance using on-board wavefront sensing (WFS) and active control (WFC). A-DOT is currently in the design phase. This paper presents the development of a deployable, single-segment, mechanical prototype. The deployable mirror segment is kinematically mounted to a monolithic flexure using three spherical contacts in a cup-grooveflat arrangement. Tip, tilt and piston (PTT) are controlled using linear, piezoelectric actuators at each contact and the mirror position measured using capacitive sensors. The prototype is packaged within the allowable CubeSat volume and uses space-compatible hardware in a non-magnetic design.
A-DOT (Active Deployable Optical Telescope) is a payload prototype project of a 6U segmented deployable telescope with an aperture diameter of 300 mm currently in the design phase. This paper investigates two different strategies for phasing a deployable segmented telescope. The first method employs a classical optimisation approach, where the image sharpness is used as the primary metric for aligning the mirror segments. This technique involves iteratively adjusting the individual segments' positions and orientations to maximise the resulting image's sharpness. The second method takes a more innovative approach by leveraging the power of deep learning techniques. Deep learning algorithms, trained on a large dataset of simulated images, can learn to recognise and correct phasing errors automatically. This approach can potentially streamline the phasing process and enhance the telescope's overall performance. Preliminary results from the study demonstrate the efficacy of both methods in achieving excellent phasing control. Remarkably, these techniques have successfully identified and corrected significant phasing errors, with path length differences of several microns, ultimately reducing the residual errors to the desired performance level using a point source, typically below 15 nm in the visible spectrum.
HARMONI is the first light visible and near-IR integral field spectrograph for the ELT. It covers a large spectral range from 450 nm to 2450 nm with resolving powers from 3500 to 18000 and spatial sampling from 60 mas to 4 mas. It can operate in two Adaptive Optics modes - SCAO (including a High Contrast capability) and LTAO - or with NOAO. The project is preparing for Final Design Reviews. HARMONI is a work-horse instrument that provides efficient, spatially resolved spectroscopy of extended objects or crowded fields of view. The gigantic leap in sensitivity and spatial resolution that HARMONI at the ELT will enable promises to transform the landscape in observational astrophysics in the coming decade. The project has undergone some key changes to the leadership and management structure over the last two years. We present the salient elements of the project restructuring, and modifications to the technical specifications. The instrument design is very mature in the lead up to the final design review. In this paper, we provide an overview of the instrument's capabilities, details of recent technical changes during the red flag period, and an update of sensitivities.
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.
Available volumes of nanosats such as CubeSats impose physical limits to the telescope diameter, limiting achievable spatial resolution and photometric capability. For example, a 12U CubeSat typically only has sufficient volume to host a 20 cm diameter monolithic telescope. In this paper, we present recent advances in deployable optics to host a 30 cm+ diameter telescope in a 6U CubeSat, with a volume of 4U dedicated to the payload and 2U to the satellite bus. To reach this high level of compactness, we fold the primary and secondary mirrors for launch, which are then unfolded and aligned in space. Diffraction-limited imaging quality in the visible part of the spectrum is achieved by controlling each mirror segment in piston, tip, and tilt. In this paper, we first describe overall satellite concept, we then report on the optomechanical design of the payload to deploy and adjust the mirrors. Finally, we discuss the automatic phasing of the primary to control the final optical quality of the telescope.
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