High spatial resolution images of the volcanic moon Io at visible and near-infrared wavelengths were obtained by the SHARK-VIS and SHARK-NIR instruments on the Large Binocular Telescope on UT 2025 February 18 and 23. Large-scale changes on Io’s surface are identified in these data and provide vital context for infrared observations from other telescopes and spacecraft. SHARK-VIS imaged part of the plume deposit from a large eruption close to Io’s south pole at Illyrikon that was first observed by NASA’s Juno spacecraft in 2024 December, detecting significant deposit modification. Examples of other significant surface changes detected include at Seth, identifying a new pyroclastic deposit in addition to the new lava flows previously detected in Juno infrared observations; at Amirani, confirming that volcanic activity was now confined to the southern half of the Galileo-epoch lava flow field; new red sulphur-rich deposits at Mixcoatl; and changes in the plume deposits around Prometheus. Plume deposits at Prometheus and at other volcanoes show evidence of complex interplay between different plumes issuing from the same volcano. The combination of SHARK-VIS and Juno JunoCam data moves closer to near-global, near-contemporaneous, visible-wavelength coverage of Io. SHARK-VIS lives up to its promise of a new era of planetary imaging at visible wavelengths and filling the temporal coverage gap between Juno and the arrival of the Europa Clipper and JUICE spacecraft in the Jovian system in 2030 and 2031, respectively.

This Primer provides an overview of a fundamental set of analysis methods for studying waves, vibrations and related oscillatory phenomena — including instabilities, turbulence and shocks — across diverse scientific fields. These phenomena are ubiquitous, from astrophysics to complex systems in terrestrial environments, and understanding them requires careful selection of techniques. Misapplication of analysis tools can introduce misleading results. In this Primer, the fundamental principles of various wave analysis methods are first reviewed, along with adaptations to address complexities such as nonlinear, non-stationary and transient signal behaviour. These techniques are applied to identical synthetic datasets to provide a quantitative comparison of their strengths and limitations. Details are provided to help select the most appropriate analysis tools based on specific data characteristics and scientific goals, promoting reliable interpretations and ensuring reproducibility. Additionally, the Primer highlights best ethical practices for data deposition and the importance of open-code sharing. Finally, the broad applications of these techniques are explored in various research fields, current challenges in wave analysis are discussed, and an outlook on future directions is provided, with an emphasis on potential transformative discoveries that could be made by optimizing and developing cutting-edge analysis methods. Waves are ubiquitous in nature and occur across various scales and settings. In this Primer, Jafarzadeh et al. discuss techniques for preprocessing and analysing waves, including information on choosing the appropriate methods based on wave properties, and present worked examples using synthetic datasets.

The superb image quality, stability and sensitivity of the JWST permit deconvolution techniques to be pursued with a fidelity unavailable to ground-based observations. We present an assessment of several deconvolution approaches to improve image quality and mitigate effects of the complex JWST point spread function (PSF). The optimal deconvolution method is determined by using WebbPSF to simulate JWST's complex PSF and MIRISim to simulate multi-band JWST/Mid-Infrared Imager Module (MIRIM) observations of a toy model of an active galactic nucleus (AGN). Five different deconvolution algorithms are tested: (1) Kraken deconvolution, (2) Richardson-Lucy, (3) Adaptive Imaging Deconvolution Algorithm, (4) Sparse regularization with the Condat-V\~u algorithm, and (5) Iterative Wiener Filtering and Thresholding. We find that Kraken affords the greatest FWHM reduction of the nuclear source of our MIRISim observations for the toy AGN model while retaining good photometric integrity across all simulated wavebands. Applying Kraken to Galactic Activity, Torus, and Outflow Survey (GATOS) multi-band JWST/MIRIM observations of the Seyfert 2 galaxy NGC 5728, we find that the algorithm reduces the FWHM of the nuclear source by a factor of 1.6-2.2 across all five filters. Kraken images facilitate detection of a SE to NW $\thicksim$2".5 ($\thicksim$470 pc, PA $\simeq$115\deg) extended nuclear emission, especially in the longest wavelengths. We demonstrate that Kraken is a powerful tool to enhance faint features otherwise hidden in the complex JWST PSF.

Since volcanic activity was first discovered on Io from Voyager images in 1979, changes on Io's surface have been monitored from both spacecraft and ground-based telescopes. Here, we present the highest spatial resolution images of Io ever obtained from a ground-based telescope. These images, acquired by the SHARK-VIS instrument on the Large Binocular Telescope, show evidence of a major resurfacing event on Io's trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images show that a plume deposit from a powerful eruption at Pillan Patera has covered part of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io's surface using adaptive optics at visible wavelengths.

Small-ELF is a 3.5-meter telescope currently in development that will serve as a technology demonstrator for the much larger telescope named ELF (Exo-Life Finder). The ELF is proposed to be built with a minimum effective diameter of 12- meters and is designed to be scalable to a much larger size. The primary objective of the proposed design approach is to radically improve the system’s capabilities for direct imaging of exoplanets while keeping costs well below the current flagship observatories. The basic optical design of Small-ELF consists of an annulus of 15 primary mirror sub-apertures, mounted on an alt-az configuration. As a technology demonstrator, the mechanical design of Small-ELF intends to deliver a versatile and reliable experimental platform to implement and verify several new techniques: the use of a tensegrity-based configuration for a light-weight supporting structure, the use of tensioned ropes to actively adjust the telescope geometry, methods of accommodating sub-apertures of significant weight variations, and methods of controlling and mitigating vibrations associated with light-weighted structures through active and passive damping systems. The design also adopts techniques for efficient precision manufacturing and cost control. The unique optical layout and application of tensegrity produce significant weight and subsequent cost reductions. This technology demonstrator tackles the cost and scalability problem faced by most existing telescopes and intends to open a new chapter in large telescope structural design methodology.

We suggest a physically motivated model of the uncorrelated background, which can be used to improve the accuracy of helioseismic frequency measurements when the background contributes significantly to the formation of spectral lines of acoustic resonances. The basic assumption of our model is that the correlation length of the convective motions is small compared with the horizontal wavelength R _⊙ / ℓ of the observations, where ℓ is the degree of the spherical harmonic Y _ℓ _m ( θ , φ ). When applied to solar power spectra at frequencies below acoustic resonances, the model reveals a distinct sensitivity to solar rotation: advection of the convective velocity pattern brings spatial correlations in the apparent stochastic velocity field (temporal correlations in the corotating frame induce spatial correlations in the inertial frame). The induced spatiotemporal correlations manifest themselves as an antisymmetric component in the dependence of the convective noise power on azimuthal order m , which allows us to address the solar differential rotation. With 360 days of data obtained by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, we measure three components of the rotation rate as a function of latitude using only ℓ = 300. This result indicates that the model suggests a new way of measuring solar subsurface rotation. This approach can complement traditional measurements based on correlation tracking.

We can deduce the activity and dynamic status of the Sun and its possible dependence on the magnetic cycle using continuous, multi-height observations of the solar atmosphere. This activity, in turn, is critical in identifying potential precursors of space weather events such as flares and coronal mass ejections. To investigate these phenomena, we describe the design and construction of a multi-nodal synoptic telescope network to observe the entire disk of the Sun: Global Automatic Telescopes for Exploring the Sun (GATES). This network currently comprises of two instruments, the Tor Vergata Solar Synoptic Telescope (TSST) under construction at Universita degli Studi di Roma Tor Vergata, to be mounted in La Palma, Canary Islands, Spain, and the Mojave Solar Observatory (MSO) located in Apple Valley, California. MSO houses a dual Na and K channel magneto-optical filter (MOF)-based telescope currently able to observe on-sky with the addition of a He MOF (to observe the upper chromosphere) currently in development. TSST consists of a lab-tested K MOF channel and a broadband Ha filter; TSST has been designed to minimize mass and allow for full automation. Both MSO and TSST have been constructed almost entirely commercially available parts, keeping the instruments low-cost and highly accessible to construct. With the completion and installation of the TSST, the two nodes will observe for an average of 20 hours a day, obtaining line-of-sight velocity and magnetic field observations (Dopplergrams and magnetograms, respectively), which we will use to analyze and predict space weather events. We show that this network consists of low-cost, robotic facilities able to achieve the necessary data for the study of space weather events. We present preliminary data obtained using the network's individual nodes and technical specifications for the future operation of the network as a whole.

We present evidence supporting wave reflection in the lower solar chromosphere based on helioseismic analysis of multi-height Doppler data from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager and the Magneto-Optical filters at Two Heights II instrument. This evidence is derived through a wave propagation model that incorporates both upward- and downward-traveling (reflected) waves. Moreover, we find that the height of the reflecting region varies with magnetic field strengths in a way that suggests a connection with the plasma β ∼ 1 region. We measure an effective reflection coefficient of 13% in a magnetically quiet region of the Sun.

AbstractSince volcanic activity was first discovered on Io from Voyager images in 1979, changes on Io's surface have been monitored from both spacecraft and ground‐based telescopes. Here, we present the highest spatial resolution images of Io ever obtained from a ground‐based telescope. These images, acquired by the SHARK‐VIS instrument on the Large Binocular Telescope, show evidence of a major resurfacing event on Io's trailing hemisphere. When compared to the most recent spacecraft images, the SHARK‐VIS images show that a plume deposit from a powerful eruption at Pillan Patera has covered part of the long‐lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth‐based telescopes. The SHARK‐VIS instrument ushers in a new era of high resolution imaging of Io's surface using adaptive optics at visible wavelengths.

The process of material aging in space has been traditionally studied using laboratory experiments and onboard experiments on the International Space Station. However, these experiments either miss crucial physics or require the materials to be held on the spacecraft and returned to Earth for analysis, where exposure to air changes the properties of the aged materials. This work aims to provide a means for measuring the reflectance spectrum of spacecraft materials, and their variations with time, using ground-based observations of the spacecraft while it is on orbit. We employ the technique of myopic deconvolution of ultra-broadband ( Δλ =600 nm ), short-exposure (“speckle") images of an object to provide a 3-D hyperspectral recovery of the target. This approach leverages the wavelength dependence of how light travels through the atmosphere and is diffracted in our instrument. We use numerical simulations to show that we can expect to successfully recover a hyperspectral image of a simple satellite observed with a 3 m class telescope and a typical sCMOS detector through moderate turbulence. The resulting hyperspectral image exhibits high spatial resolution and low to moderate spectral resolution. The actual spectral resolution depends on the signal-to-noise ratio of the data and the expected spectral complexity of the materials’ spectra. Our results provide a solid numerical proof of concept validation for improving the identification of materials on orbiting satellites using resolved ground-based observations. This study represents the first serious suggestion that the proposed technique will work effectively when applied to real-world data. These findings not only demonstrate the potential of ultra-broadband speckle imaging for characterizing satellites, but also pave the way for future studies of material aging in the space environment.

We explore the possibility of detecting very faint, very close-in stellar companions using large aperture ground-based telescopes and the technique of optical speckle imaging. We examine the state of high-angular-resolution speckle imaging and contrast levels being achieved using current speckle cameras on the Gemini 8 m telescope. We then explore the use of the modern image reconstruction technique—multiframe blind deconvolution (MFBD)—applied to speckle imaging from the Gemini 8 m telescope. We show that MFBD allows us to measure the flux ratio of the imaged stars to high accuracy and the reconstructed images yield higher precision astrometry. Both of these advances provide a large refinement in the derived astrophysical parameters compared with current Fourier techniques. MFBD image reconstructions reach contrast levels of ∼5 × 10 −3 , near the diffraction limit, to ∼10 −4 about 1.″0 away. At these deep contrast levels with angular limits starting near the 8 m diffraction limit (∼20 mas), most stellar companions to a solar-like stars can be imaged in the optical to near-IR bandpass (320–1000 nm). “To Xanadu we go...” —adapted from S. T. Coleridge.

In the context of extreme adaptive optics for large telescopes, we present the Kraken multi-frame blind deconvolution (MFBD) algorithm for processing high-cadence acquisitions, capable of providing a diffraction-limited estimation of the source brightness distribution. This is achieved by a data modeling of each frame in the sequence driven by the estimation of the instantaneous wave front at the entrance pupil. Under suitable physical constraints, numerical convergence is guaranteed by an iteration scheme starting from a compact MFBD, which provides a very robust initial guess that only employs a few frames. We describe the mathematics behind the process and report the high-resolution reconstruction of the spectroscopic binary α And (16.3 mas separation) acquired with the precursor of SHARK-VIS, the upcoming high-contrast camera in the visible for the Large Binocular Telescope.

The small ExoLife Finder (sELF) telescope is a 3.4m diameter fixed pupil tracking Fizeau interferometer. Its design relies on several new technologies the ELF-PLANETS consortium has championed that will enable large narrow-field optical coronagraphic direct imaging. These distinguish it from other segmented aperture telescopes by its light weight, low cost, and its capability to create a coronagraphic point spread function with the telescope pupil, ahead of the secondary optics. This diffractive control emphasizes high dynamic range imaging in the presence of a bright central star in a narrow field-of-view. Its optomechanical design uses elements of tensegrity combined with thin (2mm thick by 0.5m diameter) off-axis parabola segments to decrease both the optical payload and mechanical structural mass. The sELF optomechanical design has been completed and contracts for construction in the Canary Islands will be tendered during the 1st quarter of 2023

Willson was an expert in ground-based high angular resolution imaging. He studied planet formation in young stellar disks and helped develop software for wavefront sensing with the European Extremely Large Telescope.

Matthew Willson (1990–2022) Stefan Kraus and colleagues remember a charismatic colleague whose career in observational astronomy ended far too soon. High angular resolution astronomy has suffered a great loss with the sudden death of Dr. Matthew Willson at age 31. Matthew was visiting his long-time girlfriend Katherine Shepard (a PhD student in astronomy at Georgia State University in Atlanta) when he was struck by a stray gunshot that entered the apartment where he was staying. He died in hospital a few days later on 18 January 2022. This tragic and premature end to the life of such a promising young scientist has devastated his many colleagues on both sides of the Atlantic. Matthew Willson was born in London on 18 March 1990. He loved the stars from his earliest years, and, blessed with an amazing memory, he was on his way to a lifetime of learning. He began his formal life in astrophysics as a student (2008–12) at Royal Holloway, University of London, just down the road from his childhood home. There he worked with Stewart Boogert on the design, construction, and calibration of a spectrometer for use with the university's 30 cm telescope. He led students on many cold evenings, teaching telescope use and wrestling equipment into operation for programmes of photometry and spectroscopy.