Whether cluster mergers enhance ram pressure stripping (RPS) and accelerate member galaxy evolution remains an open question. Here, we investigate galaxy populations in the nearby merging cluster Abell 3667 (z≃0.0553) using spatially resolved data from the Hector Galaxy Survey. We define an RPS sample combining Hector-selected galaxies with ionised gas disturbances (e.g., asymmetric tails or truncated disks) and supplementary, optically identified jellyfish galaxies lacking Hector data. Most of the RPS sample (∼ 71^+10_-7%; 20/28) lies within R_200, where the merger impact is greater. Most asymmetric galaxies (∼ 73^+14_-8%; 11/15), especially those with extreme RPS signatures, are concentrated in the inner cluster (R ≲ 0.6 R_200), along the merger axis between two shock-tracing radio relics. These central asymmetric galaxies show two spatial and kinematic groups: one at the North-West (NW) subcluster, downstream of its radio relic in a region of high-velocity intracluster medium (ICM) bulk motion, with blueshifted line-of-sight velocities; and a mostly redshifted population near the main cluster (MC), which also shows a turbulent ICM. Despite their projected association with the MC core and NW substructure, both samples' velocities indicate they are not bound to them. Tail orientations give insight into orbital histories: NW tails point away from the cluster centre and often align with the merger axis, suggesting merger-driven stripping, while MC tails show neither pattern clearly. Tails are broadly westward, with MC tails tracing due west and NW tails shifted northwest, pointing to two distinct filamentary accretion events for the NW and MC populations. Together, our results indicate enhanced RPS in the heart of A3667, driven mainly by infalling galaxies accreted along nearby filaments interacting with the merger-driven turbulent environment.

The Hector Galaxy Survey is a new optical integral field spectroscopy (IFS) survey currently using the Anglo-Australian Telescope to observe up to 15 000 galaxies at low redshift ( $z \lt 0.1$ ). The Hector instrument employs 21 optical fibre bundles feeding into two double-beam spectrographs, AAOmega and the new Spector spectrograph, to enable wide-field multi-object IFS observations of galaxies. To efficiently process the survey data, we adopt the data reduction pipeline developed for the SAMI Galaxy Survey, with significant updates to accommodate Hector's dual-spectrograph system. These enhancements address key differences in spectral resolution and other instrumental characteristics relative to SAMI and are specifically optimised for Hector's unique configuration. We introduce a two-dimensional arc fitting approach that reduces the root-mean-square (RMS) velocity scatter by a factor of 1.2-3.4 compared to fitting arc lines independently for each fibre. The pipeline also incorporates detailed modelling of chromatic optical distortion in the wide-field corrector, to account for wavelength-dependent spatial shifts across the focal plane. We assess data quality through a series of validation tests, including wavelength solution accuracy (1.2-2.7 km s $<^>{-1}$ RMS), spectral resolution (FWHM of 1.2-1.4 & Aring; for Spector), throughput characterisation, astrometric precision ( $\lesssim$ 0.03 arcsec median offset), sky subtraction residuals (1-1.6% median continuum residual), and flux calibration stability (4% systematic offset when compared to Legacy Survey fluxes). We demonstrate that Hector delivers high-fidelity, science-ready datasets, supporting robust measurements of galaxy kinematics, stellar populations, and emission-line properties and provide examples. Additionally, we address systematic uncertainties identified during the data processing and propose future improvements to enhance the precision and reliability of upcoming data releases. This work establishes a robust data reduction framework for Hector, delivering high-quality data products that support a broad range of extragalactic studies.

Hector is a new optical integral field spectrograph (IFS) instrument built by Astralis - Australia's Astronomical Instrumentation Consortium. Hector was commissioned on the Anglo-Australian Telescope (AAT) in 2022. In 2023 it began a 15,000-galaxy IFS survey of nearby z< 0.1 galaxies. The high fill-factor imaging fibre bundles 'hexabundles' of the type used on the SAMI instrument, have been improved and enlarged to cover up to 27-arcsec diameter. The aim is to reach 2 effective radii on most galaxies. Hector has a unique and novel robotic positioner that compensates for varying telecentricity over the 2-degree-field of the AAT to recoup the light loss and correct the focus across the field. Hector has 21 hexabundles over that 2-degree field feeding both the new Hector spectrograph (Spector) and existing AAOmega spectrograph. The new dual-arm Spector spectrograph has the highest spectral resolution of any large IFS nearby galaxy survey of 1.3 Angstrom. This is key to enable higher order stellar kinematics to be measured on a larger fraction of galaxies and to link those galaxies to the large-scale environments in which they form. A data reduction pipeline has been developed and is producing science-quality galaxy cubes and the first internal data release is now being used for science.

The Keck Wide Field Imager (KWFI) is a 1-degree field of view imager optimized to take advantage of the UV performance of the W.M. Keck Observatory located atop Mauna Kea in Hawaii. The project is an international collaboration between Swinburne University, ANU, AAO-Macquarie, Caltech, UC Observatories, and W.M. Keck Observatory. KWFI fills the 8m-class capability gap for deep, blue wide-field imaging and rapid-response follow-up necessary for many science cases, including cosmic reionization, transient astronomy at all wavelengths and messengers, and space mission main science aims. The instrument has a high-throughput, UV-sensitive design with an all-fused silica 4-lens element corrector system that operates from 300 - 1000 nm and achieves 0.4" 80% encircled energy diameter rms over the FOV within each photometric band. In 2022, we reported on the conceptual design of the imager that includes fast (similar to 10 s) filter exchange of its 600 mm narrowband and broadband filters, fast (seconds) image processing and source identification, and CCD and CMOS detectors. More recently, the team has advanced the development of a Deployable Secondary Mirror (DM2), which will work with KWFI. The DM2 is a 1.4-meter lightweight, remotely deployable hexagonal secondary mirror to allow fast switching between KWFI and any Cassegrain or Nasmyth Instruments to enable rapid spectroscopic follow up of identified sources. We report here on the DM2 conceptual design, progress on the imager design, testing of the prototype filter exchange mechanism, and the interface of KWFI and the DM2 with the 30-year-old Keck Telescope.

Since the start of science operations in 1993, the twin 10-m W. M. Keck Observatory (WMKO) telescopes have continued to maximize their scientific impact and to produce transformative discoveries that keep the observing community on the frontiers of astronomical research. Upgraded capabilities and new instrumentation are provided through collaborative partnerships with Caltech, the University of California, and the University of Hawaii instrument development teams along with industry and other organizations. The observatory adapts and responds to the observers' evolving needs as defined in the observatory's strategic plan periodically refreshed in collaboration with the science community. This paper is an overview of the instrumentation projects that range from commissioning to early conceptual stages. An emphasis is placed on the detector, detector controllers, and capability needs that are driven by the desired future technology defined in the 2022 strategic plan.

Subaru Nasmyth Beam-Switcher (SNBS) is an instrument designed for Nasmyth platform at Subaru telescope. It is a relay optics system which switches the light downstream of AO188 and LTAO to multiple instruments and allow multiple instruments work simultaneously with Subaru Coronagraphic Extreme Adaptive Optics system (SCExAO). The design has been completed and is now in building phase. The instrument working wavelength range is from 0.5μm to 5.3μm with field of view of 75 arcsecs in diameter. In this paper, we present its optical design and performance at different exit bays with various adaptive optics (AO) configurations. The wavefront at SCExAO bay is investigated. Tolerance and thermal performance of the switcher is also presented.

The Australian Astronomical Observatory’s (AAO’s) AESOP project is part of the Multi-Object Spectrograph Telescope (4MOST) system for the VISTA telescope. It includes the 2436-fibre positioner, space frame and electronics enclosures. The AESOP concept and the role of the AAO in the 4MOST project have been described in previous SPIE proceedings. The project final assembly stage has recently been completed. In this paper, key results in accurate manufacturing and assembly of critical AESOP components are discussed. The major performance requirement for AESOP is that all 2436 science fibre cores and 12 guide fibre bundles are to be re-positioned to an accuracy of 10 micron within 1 minute. With a fast prime-focus focal-ratio, a close tolerance of +/-70 microns on the axial position of the fibre tips must be held so efficiency does not suffer from de-focus losses. Positioning accuracy is controlled with the metrology cameras installed on the telescope, which measures the positions of the fibre tips to an accuracy of a few micrometers and allows iterative positioning until all fibre tips are within tolerance on the ultimate position. Maintaining co-planarity of the fibre tips requires accurate control in the assembly of several components that contribute to such errors. Overall, the AESOP design fully complies with all its requirements and in most cases achieves its goals. A thorough consideration of all the relevant interfaces during the design and assembly phases, has resulted in comprehensive set of ICDs for the mechanical, electrical and software aspects of AESOP.

The Keck Wide Field Imager (KWFI) is a 1-degree field of view imager optimized to take advantage of the superb UV performance of the W.M. Keck Observatory (WMKO) located atop Mauna Kea in Hawaii. The project is an international collaboration between Swinburne University, ANU Macquarie University, Caltech, UC Observatories, and W.M Keck Observatory. KWFI is an all-fused silica 4-lens element corrector that operates over u,g,r,i, and z photometric bands from 300 – 1000 nm where the design achieves 0.5” 80% encircled energy diameter rms over the FOV within each photometric band. The KWFI collaboration is completing an 18-month conceptual design phase and is preparing to issue the most critical, long-lead-time procurements to address the critical path to first-light operations, following a public/private fundraising model. Our technically paced schedule, driven by corrector lens figuring, is expected to culminate in KWFI First Light in Summer 2027. We report here on the instrument concept and the progress towards a significant new capability for the WMKO.

The Australian Astronomical Observatory’s (AAO’s) AESOP project is part of the Multi-Object Spectrograph Telescope (4MOST) system for the VISTA telescope. It includes the 2436-fibre positioner, space frame and electronics enclosures. The AESOP concept and the role of the AAO in the 4MOST project have been described in previous SPIE proceedings. The project final assembly stage has been completed. In this paper, engineering principles applied during assembly of critical components and testing of the instrument are discussed. The major performance requirement for AESOP is that all 2436 science fiber cores and 12 guide fiber bundles are to be re-positioned to an accuracy of 10 micron within 1 minute. With a fast prime-focus focal-ratio, a close tolerance on the axial position of the fiber tips must be held so efficiency does not suffer from de-focus losses. Positioning accuracy is controlled with the metrology cameras installed on the telescope, which measures the positions of the fiber tips to an accuracy of a few micrometers and allows iterative positioning until all fiber tips are within tolerance on the focal surface plane. Maintaining co-planarity of the fiber tips requires accurate control in the assembly of several components that contribute to such errors. AESOP requires a consistent production of high accuracy components and assemblies in a quantity of above 2500 items. To achieve this, we had to apply the highest engineering standards, including assembly procedures, metrology, and control systems. We designed many jigs and fixtures, which enabled us to produce high quality components and assemblies at reasonable cost. The results – working instrument was vastly achieved with the help of university students after providing a training in engineering practices.

A few telescope projects plan to feed spectrographs through thousands of fibres, needing metrology accuracy for feedback of just a few mu m. This generally requires accuracy at the metrology camera better than 0.1 arcsec, which can be frustrated by local seeing. With fiducials situated with the array of science fibres, seeing displacements can be calibrated, with accuracy depending on the fiducial spacing. Fiducials within the field usually require sacrificing science fibres but AAO's positioner for MSE will take advantage of its tilting spines and a special but simple metrology camera to provide a multitude of fiducials within the field with no such sacrifice.

We discuss the Maunakea Spectroscopic Explorer (MSE) Acquisition and Guide (A and G) System conceptual focal plane hardware and operational requirements and pay detailed attention to the A and G system’s three CMOS cameras’ areas and sensitivities needed to assure a high success rate in acquiring suitable guide stars. Ways to provide auxiliary functions, including the measurement of defocus and misalignment of the telescope optics, are also discussed.

Based on the success of the SAMI integral field spectrograph (IFS) instrument on the Anglo-Australian Telescope (AAT), the capacity for large IFS nearby galaxy surveys on the AAT is being substantially expanded with a new instrument, Hector. The high fill-factor imaging fibre bundles ‘hexabundles’, of the type used on SAMI, are being improved and enlarged to cover 27-arcsec diameter. The aim is to reach 2 effective radii on most galaxies, where the galaxy rotation curve flattens and half of the angular momentum is accounted for. The boosted Hector spectral resolution of 1.3 Angstrom will enable higher order stellar kinematics to be measured on a larger fraction of galaxies than with any other IFS survey instrument. Hector will have 21 hexabundles over a 2-degree field feeding both the new Hector spectrograph and existing AAOmega spectrograph. Hector consists of new blue and red-arm spectrographs, coupled to the new high- efficiency hexabundles and a unique robotic positioner. The novel robotic positioning concept will compensate for varying telecentricity over the 2-degree-field of the AAT to recoup the light loss and correct the focus across the field. The main components are in hand, and prototypes are currently being tested ahead of commissioning in the next year. Hector will take integral field spectroscopy of 15,000 galaxies with z < 0.1 in the 4MOST WAVES-North and WAVES-South regions. The WAVES data, which will come later, will give the environment metrics necessary to relate how local and global environments influence galaxy growth through gas accretion, star formation and spins measured with Hector. The WALLABY ASKAP survey will trace HI gas across the Hector fields, which in combination with Hector will give a complete view of gas accretion and star formation.

MANIFEST is a multi-object fibre positioner for the Giant Magellan Telescope that uses ‘Starbug’ robots to accurately position fibre units across the telescope’s focal plane. MANIFEST, when coupled to the telescope’s planned seeing-limited instruments, GMACS and GCLEF, offers access to: larger fields of view; higher multiplex gains; versatile focal plane reformatting of the focal plane via multiple integral-field-units; increased spectral resolution using image-slicers; the capability for simultaneous observations with multiple instruments; the possibility of a gravity-invariant spectrograph mounting; the potential for OH suppression via fiber systems in the near-infrared; and the versatility of adding new instruments in the future. We have now completed the pre-concept phase for MANIFEST. This phase has focused on developing the science case and requirements, further developing high risk aspects of the instrument design, designing the opto-mechanical interfaces to the GMACS and GCLEF instruments, and detailing the interfaces to the GMT.

Many areas of astronomical research rely on deep blue wide-field imaging. Mauna Kea enjoys the very best UV transparency from the ground and the Keck telescopes with 10 meter f/1.75 primaries are well suited to a prime focus camera with a large angular field. Swinburne University leads a proposal to provide a camera (KWFI, for Keck Wide Field Imager) that is optimized in the UV but works well to 1μm wavelength. Keck has interchangeable top end modules, of which one is now unused and easily capable of housing the required corrector lens and detector enclosure. This paper concentrates on details of the KWFI optical design.

We introduce the 4-metre Multi-Object Spectroscopic Telescope (4MOST), a new high-multiplex, wide-field spectroscopic survey facility under development for the four-metre-class Visible and Infrared Survey Telescope for Astronomy (VISTA) at Paranal. Its key specifications are: a large field of view (FoV) of 4.2 square degrees and a high multiplex capability, with 1624 fibres feeding two low-resolution spectrographs ($R = \lambda/\Delta\lambda \sim 6500$), and 812 fibres transferring light to the high-resolution spectrograph ($R \sim 20\,000$). After a description of the instrument and its expected performance, a short overview is given of its operational scheme and planned 4MOST Consortium science; these aspects are covered in more detail in other articles in this edition of The Messenger. Finally, the processes, schedules, and policies concerning the selection of ESO Community Surveys are presented, commencing with a singular opportunity to submit Letters of Intent for Public Surveys during the first five years of 4MOST operations.

In this paper we present the Australian Astronomical Observatory's concept design for Sphinx - a fiber positioned with 4332 spines on a 7.77mm pitch for CFHT's Mauna Kea Spectroscopic Explorer (MSE) Telescope. Based on the Echidna technology used with FMOS (on Subaru) and 4MOST (on VISTA), the next evolution of the tilting spine design delivers improved performance and superior allocation efficiency. Several prototypes have been constructed that demonstrate the suitability of the new design for MSE. Results of prototype testing are presented, along with an analysis of the impact of tilting spines on the overall survey efficiency. The Sphinx fiber positioned utilizes a novel metrology system for spine position feedback. The metrology design and the careful considerations required to achieve reliable, high accuracy measurements of all fibres in a realistic telescope environment are also presented.

Maunakea Spectroscopic Explorer will be a 10-m class highly multiplexed survey telescope, including a segmented primary mirror and robotic fiber positioners at the prime focus. MSE will replace the Canada France Hawaii Telescope (CFHT) on the summit of Mauna Kea, Hawaii. The multiplexing includes an array of over four thousand fibers feeding banks of spectrographs several tens of meters away. We present an overview of the requirements flow-down for MSE, from Science Requirements Document to Observatory Requirements Document. We have developed the system performance budgets, along with updating the budget architecture of our evolving project. We have also identified the links between subsystems and system budgets (and subsequently science requirements) and included system budget that are unique to MSE as a fiber-fed facility. All of this has led to a set of Observatory Requirements that is fully consistent with the Science Requirements.

MANIFEST is a multi-object fibre facility for the Giant Magellan Telescope that uses ‘Starbug’ robots to accurately position fibre units across the telescope’s focal plane. MANIFEST, when coupled to the telescope’s planned seeinglimited instruments, offers access to larger fields of view; higher multiplex gains; versatile focal plane reformatting of the focal plane via integral-field-units; image-slicers; and in some cases higher spatial and spectral resolution. The TAIPAN instrument on the UK Schmidt Telescope is now close to science verification which will demonstrate the feasibility of the Starbug concept. We are now moving into the conceptual development phase for MANIFEST, with a focus on developing interfaces for the telescope and for the instruments.

In this paper we present recent progress on the Australian Astronomical Observatory's AESOP(2) fiber positioner for 4MOST (on VISTA). As an evolution of the Echidna "spine" technology used for FMOS (on Subaru), AESOP has challenging requirements to position 2,448 fibers in parallel, within 1 minute, to an accuracy of < 10 um RMS. AESOP successfully passed ESO's official final design review and manufacturing has commenced. We present performance results from the first batch of newly-manufactured positioners and also report on how the AESOP project is tracking in terms of schedule, budget and risk.

The Australian Astronomical Observatory's (AAO's) AESOP project is part of the 4 metre Multi-Object Spectrograph Telescope (4MOST) system for the VISTA telescope. It includes the 2436-fiber positioner, space frame and electronics enclosures. The AESOP concept and the role of the AAO in the 4MOST project have been described in previous SPIE proceedings. Prototype tests, which were completed early in 2017 demonstrated that the instrument requirements are satisfied by the design. The project final design stage has recently been completed. In this paper, key features of the AESOP positioning system design, along with the techniques developed to overcome key mechanical, electronic, and software engineering challenges are described. The major performance requirement for AESOP is that all 2436 science fiber cores and 12 guide fiber bundles are to be re-positioned to an accuracy of 10 mu m within 1 minute. With a fast prime-focus focal-ratio, a close tolerance on the axial position of the fiber tips must be held so efficiency does not suffer from de-focus losses. Positioning accuracy is controlled with the metrology cameras installed on the telescope, which measures the positions of the fiber tips to an accuracy of a few ae m and allows iterative positioning until all fiber tips are within tolerance. Maintaining co-planarity of the fiber tips requires accurate control in the assembly of several components that contribute to such errors. Assembly jigs have been developed and proven adequate for this purpose. Attaining high reliability in an assembly with many small components of disparate materials bonded together, including piezo ceramics, carbon fiber reinforced plastic, hardened steel, and electrical circuit boards, has entailed careful selection and application of cements and tightly controlled soldering for electrical connections.