PyCPL provides full access to ESO's Common Pipeline Library ( CPL) for astronomical data reduction within a Python environment. Not only does it offer a Python interface to the robust CPL library, but it also lets users and developers fully utilise the rest of the scientific Python ecosystem. We have written a C++ layer to CPL and with pybind11 (a third-party library) created a Pythonic API to CPL. Since CPL has been around for so long, it has been thoroughly tested and understood. In 2003 it was developed in C due to its efficiency and speed of execution. With the community however moving away from C/C++ programming and embracing Python for data processing tasks, there is a need to provide access to the CPL utilities within a Python environment. With the latest version being released users can now install PyCPL to run existing CPL recipes (written in C) and access the results from Python. It also provides the ability to create new recipes in Python using the functionality provided by CPL.

MAVIS is the world’s first facility-grade visible MCAO instrument, currently under development for the VLT. The AO system will feed an imager and an integral field spectrograph, with 50% sky coverage at the Galactic pole. MAVIS has unique angular resolution and sensitivity at visible wavelengths, and is highly complementary to both JWST and ELTs. We describe both instruments in detail and the broad range of science cases enabled by them. The imager will be diffraction-limited in V, with 7.36 mas per pixel covering a 30” FOV. A set of at least 7 broad-band and 15 narrow-band filters will provide imaging from u to z. The spectrograph uses an advanced image slicer with a selectable spatial sampling of 25 or 50 mas to provide integral field spectroscopy over a FOV of 2.5”x3.6”, or 5”x7.2”. The spectrograph has two identical arms each covering half the FOV. Four interchangeable grisms allow spectroscopy with R=5,000 to R=15,000, from 380-950 nm.

The ESO Common Pipeline Library (CPL) and High Level Data Reduction Library (HDRL) together form a comprehensive, efficient and robust software toolkit for data reduction pipelines. They were developed in C for reasons of efficiency and speed, however, with the community's preference towards Python for algorithm prototyping and data reduction, there is a need for access from Python. PyCPL and PyHDRL provide this, making it possible to run existing CPL data reduction recipes from Python as well as developing new recipes in Python. These new recipes are built using the PyCPL and PyHDRL libraries, which provide idiomatic Python interfaces to CPL and HDRL while allowing users to take advantage of the scientific Python ecosystem. PyCPL and PyHDRL are already being used to prototype recipes for the MAVIS instrument pipeline, and have been used to develop an extensible pipeline development framework. Here we describe their design, implementation and usage.

Despite Python being the preferred programming language of choice for most astronomers, building or extending data reduction pipelines in the language can be problematic. A common approach is to write Python functions or classes as wrappers, calling individual pipeline recipes underneath, but this does not scale well with increasing pipeline complexity. Data management is also fraught since housekeeping code must be written to carefully handle input and output products between recipes. We have addressed these issues by creating an extensible pipeline development framework that leverages the Python bindings for the ESO Common Pipeline Library (PyCPL) toolkit. Pipeline recipes can be defined in a regulated manner using existing ESO pipeline recipes or new Python recipes compliant with ESO standards. Users can easily build their own pipeline workflows for execution by the PyCPL companion package PyEsorex. The ability to define Python recipes offers a powerful means to extend existing ESO pipelines or develop entirely new pipelines. An overview of the framework is presented along with an illustrative MUSE pipeline workflow.

SkyHopper is a proposed CubeSat mission to simultaneously observe 4 bands in the wavelength range from 0.8 to 1.7 micron. The light is captured by a telescope with a 100 mm × 200 mm primary and a field of view of 0.6° × 2.6°. A preliminary definition (phase B) of the optical telescope assembly for the mission is now completed. It is designed to make high precision intensity measurements of every object in the field of view. This brought a series of constraints to avoid stray light. Different optical designs were studied. A Kösters prism is used to split the light into 4 bands on a 2k x 2k detector. The telescope design is based on a 3 mirror anastigmat with additional lenses to provide good image quality in the final focal plane for all bands and also in the intermediate focal plane and the pupil plane where cold stops are needed. Aberrations and vignetting of the prism had to be removed. Science applications include exoplanet transits in front of low-mass stars, rapid Infrared follow-up of Gamma Ray Bursts and exploring the Cosmic Infrared Background.

MAVIS is the next instrument to go on the VLT. It is an imager and IFU spectrograph fed by Multi-Conjugate Adaptive Optics. It is presently in Phase-B (Preliminary Design Phase). The spectrograph will be preceded by an Integral Field Unit (IFU) with a choice of fields of 3.6"x2.5" with square spaxels 25 mas wide or 7.2"x5.0" with 50 mas spaxels. Two sets of interchangeable fore-optics permit the change of field size. The IFU will be based on the concept of Advanced Image Slicer present in many instruments as MUSE and KMOS on the VLT. In the present design, the field is first split in 2 and each subfield is imaged on a slicer mirror array made of long thin mirrors that slice the field into 50 images and send them in different directions to be reimaged side by side on the slit by another mirror array. A final and third mirror array on the slit places the pupil of each slice image at the right place in the spectrograph. Toroidal surfaces in each fore optics arm give the 2X magnification needed in the spectral direction. Each of the 2 subfields has its own lens spectrograph with a 9k x 9k detector and 4 interchangeable grisms giving a resolution from 5000 to 15000. High transmission glasses are used to ensure excellent throughput across the full wavelength range into the blue, covering 370- 950 nm. The slice width being near the diffraction limit, special consideration was given to the diffraction focal ratio degradation.

The TAIPAN instrument is installed on the UK Schmidt Telescope and has undergone 5 years of commissioning and verification. It utilizes the Starbug fibre positioning technology and is a proof-of-concept design for future Starbug-based instrumentation. The installation and commissioning of this new technology has provided opportunities to understand the Starbugs in detail. Science verification began in 2021 and has demonstrated the sub-10 minute configuration time, efficiency of small field ‘tweaks’ to correct for atmospheric refraction, and positioning accuracy of the Starbugs. Lessons learned from the commissioning of TAIPAN will directly impact future projects in which the Starbug technology is proposed, such as MANIFEST and FOBOS.

The Starbug technology(1) developed by AAO-MQ allows fibre positioners to be built with large multiplexing capabilities. The Starbug robots are positionable individually and in parallel, which results in significant configuration time improvements over what can be achieved by single-arm pick and place robots. Their design allows the Starbugs to carry a complex payload, and their movement mechanism and vacuum adhesion to the instrument's glass field plate at the telescope's focal plane means that they can be used to position fibres on a non-planar surface.

The Huntsman Telescope* is a wide field imager based on the successful Dragonfly Telescope concept.1 It consists of an array of co-aligned telephoto DSLR lenses with cooled CCD cameras. The ten 140 mm apertures have a combined collecting area equivalent to a 0.5 m class telescope but have lower stray light levels than a typical telescope of this size.1, 2 Its primary purpose is low surface brightness imaging of nearby galaxies, and it also observes exoplanet transits and other optical transients.

The MCAO Assisted Visible Imager and Spectrograph (MAVIS) is a facility-grade visible MCAO instrument, currently under development for the Adaptive Optics Facility at the VLT. The adaptive optics system will feed both an imager and an integral field spectrograph, with unprecedented sky coverage of 50% at the Galactic Pole. The imager will deliver diffraction-limited image quality in the V band, cover a 30" x 30" field of view, with imaging from U to z bands. The conceptual design for the spectrograph has a selectable field-of-view of 2.5" x 3.6", or 5" x 7.2", with a spatial sampling of 25 or 50 mas respectively. It will deliver a spectral resolving power of R=5,000 to R=15,000, covering a wavelength range from 380 - 950 nm. The combined angular resolution and sensitivity of MAVIS fill a unique parameter space at optical wavelengths, that is highly complementary to that of future next-generation facilities like JWST and ELTs, optimised for infrared wavelengths. MAVIS will facilitate a broad range of science, including monitoring solar system bodies in support of space missions; resolving protoplanetary- and accretion-disk mechanisms around stars; combining radial velocities and proper motions to detect intermediate-mass black holes; characterising resolved stellar populations in galaxies beyond the local group; resolving galaxies spectrally and spatially on parsec scales out to 50 Mpc; tracing the role of star clusters across cosmic time; and characterising the first globular clusters in formation via gravitational lensing. We describe the science cases and the concept designs for the imager and spectrograph.

The Huntsman Telescope, located at Siding Spring Observatory in Australia, is a system of ten telephoto Canon lenses designed for low surface brightness imaging in the Southern sky. Based upon the Dragonfly Telephoto Array, the refractive lens-based system provides an obstruction free optical path, which reduces the number of scattering surfaces and allows easier access to lower surface brightness levels. In this proceeding, we present an analysis of the impact of flat fielding uncertainty on the limiting low surface brightness levels. We show that a fairly standard set of flat-field data can be well-characterised to a $\sim0.1\%$ level. This corresponds to a 5-$\sigma$ lower limit of $\sim33$ magnitude per arcsecond$^2$, which means that flat fielding is not likely going to set Huntsman's low surface brightness limit. We also present early results of an exoplanet transient mode for Huntsman where all lenses work together to detect subtle variations in the luminosity of relatively bright $V=8-12$ magnitude stars. High-precision exoplanet imaging is ultimately limited by systematic uncertainties, so we anticipate multiple lenses will help to mitigate issues related to pixel-to-pixel and intra-pixel sensitivity variations. Our initial results show we can easily get $\sim0.4\%$ photometric precision with a single, defocused lens.

MAVIS, the Multi-conjugate Adaptive-optics Visible Imager-Spectrograph is an instrument being built for the Very Large Telescope Adaptive Optics Facility. The exquisite angular resolution provided by the AO module -in combination with the AOFwill be exploited by a 4kx4k imager and a monolithic IFU covering the optical region. MAVIS is currently in phase A (conceptual design), and the consortium just passed the phase A mid-term review. In this paper, we introduce the project, detail trade-off studies and provide a snapshot of the numerical simulations and current design choices. MAVIS is shaping up to be a truely amazing facility, providing 3× the HST angular resolution with better sensitivity on point sources. MAVIS will be a workhorse facility instrument for the VLT into the 2030s, complementing very effectively facilities like the ELTs, and facing little competition in the current astronomical instrumentation landscape.

Given enough exposure time the sensitivity of an astronomical instrument is ultimately limited by systematic errors, and the dominant source of systematic errors for most optical/infrared instruments is imperfect sky subtraction. In turn the limiting factor for sky subtraction accuracy is frequently the accuracy of flat field calibration, making these calibrations critical to the overall performance of the instrument. The Anglo-Australian Telescope’s fibre-fed spectrographs, and in particular the multi-object integral field spectrograph SAMI, are reaching sky subtraction systematic error limits and this has motivated an upgrade to the calibration systems. SAMI and its successor HECTOR are calling for sky subtraction accuracies of at least 0.25%, with a goal of 0.06%, an improvement of 4-17 times. Flat field calibrations can use dark sky, twilight sky or an illuminated screen (‘dome flats’). For multi-object spectrographs such as SAMI recalibration is required for each set of targets. This makes twilight flats impractical as it is impossible to guarantee the availability of clear twilight sky for every configuration. The dark night sky is the ideal calibrator, but the long integration times required result in onerous overheads. What is needed is a dome flat field system accurate enough to replace dark sky flats. To achieve this we have replaced both the existing screen and its illumination system. The effective throughput of optical fibres feeding an instrument vary slightly as their paths change, so high accuracy demands that calibration be done with the telescope in the same position as the science observations. We have applied two new screens to the dome windscreen, either side of the aperture, so that it is possible to move a screen in front of the telescope while in any position. There are two distinct purposes for flat fielding: photometric calibration and sky subtraction. For an ideal telescope these are equivalent but the existence of stray light creates subtle differences, and this has implications for design of the screen. When the primary purpose is sky subtraction the highest possible accuracy will be achieved with a screen that illuminates the telescope from all the directions that the night sky does. Consequently our screens match the size, shape and relative position of the windscreen aperture. The screens are implemented as Avian D diffuse reflectance coating applied to the dome windscreen itself. Avian D is highly Lambertian, has high reflectance and is durable enough for the observatory environment. The screens must be illuminated uniformly, in terms of spatial variations of both total intensity and spectral energy distribution (SED). We use an array of lamps around the end of the telescope tube. By using LEDs we are able to customise the SED and obtain a signal to noise ratio that is more consistent across wavelengths than is possible with traditional quartz tungsten halogen flat field lamps. We present the design of the new flat field calibration system, explain the main design decisions and discuss results from commissioning. These include comparisons between dome and dark sky flats, and measurements of the sky subtraction accuracy.

VELOCE is an IFU fibre feed and spectrograph for the AAT that is replacing CYCLOPS2. It is being constructed by the AAO and ANU. In this paper we discuss the design and engineering of the IFU/fibre feed components of the cable. We discuss the mode scrambling gain obtained with octagonal core fibres and how these octagonal core fibres should be spliced to regular circular core fibres to ensure maximum throughput for the cable using specialised splicing techniques. In addition we also describe a new approach to manufacturing a precision 1D/2D array of optical fibres for some applications in IFU manufacture and slit manufacture using 3D printed fused silica substrates, allowing for a cheap substitute to expensive lithographic etching in silicon at the expense of positional accuracy. We also discuss the Menlo Systems laser comb which employs endlessly-singlemode fibre to eliminate modal noise associated with multimode fibre transmission to provide the VELOCE spectrograph with a stable and repeatable source of wavelength calibration lines.

The TOLIMAN space telescope is a low-cost, agile mission concept dedicated to astrometric detection of exoplanets in the near-solar environment, and particularly targeting the Alpha Cen system. Although successful discovery technologies are now populating exoplanetary catalogs into the thousands, contemporary astronomy is still poorly equipped to answer the basic question of whether there are any rocky planets orbiting any particular star system. Toliman will make a first study of stars within 10 PC of the sun by deploying an innovative optical and signal encoding architecture that leverages the most promising technology to deliver data on this critical stellar sample: high precision astrometric monitoring. Here we present results from the Foundational Mission Study, jointly funded by the Breakthrough Prize Foundation and the University of Sydney which has translated innovative underlying design principles into error budgets and potential spacecraft systems designs.

The Australian Space Eye is a proposed astronomical telescope based on a 6U CubeSat platform. The Space Eye will exploit the low level of systematic errors achievable with a small space based telescope to enable high accuracy measurements of the optical extragalactic background light and low surface brightness emission around nearby galaxies. This project is also a demonstrator for several technologies with general applicability to astronomical observations from nanosatellites. Space Eye is based around a 90 mm aperture clear aperture all refractive telescope for broadband wide field imaging in the i' and z' bands.

The Astropy Project (http://astropy.org) is, in its own words, "a community effort to develop a single core package for Astronomy in Python and foster interoperability between Python astronomy packages." For five years this project has been managed, written, and operated as a grassroots, self-organized, almost entirely volunteer effort while the software is used by the majority of the astronomical community. Despite this, the project has always been and remains to this day effectively unfunded. Further, contributors receive little or no formal recognition for creating and supporting what is now critical software. This paper explores the problem in detail, outlines possible solutions to correct this, and presents a few suggestions on how to address the sustainability of general purpose astronomical software.