The Cryogenic Anticoincidence (CryoAC) detector is a critical subsystem designed to reduce the particle background for the X-ray Integral Field Unit (X-IFU) instrument onboard the NewAthena space observatory, the next ESA X-ray Large mission. Advancing this technology to Technology Readiness Level 5 (TRL5) requires a unified validation spanning both cleanroom microfabrication repeatability and mK low temperature operational performance. This work presents the complete development cycle of the Demonstration Model 1.2 (DM 1.2), which is aimed at completing the TRL5 demonstration path featured by all the critical technologies operating simultaneously. First, single-process verification protocols were established for Iridium pulsed laser deposition, Reactive Ion Etching (RIE), and deep silicon trenching via the Bosch process. Second, three identical single-pixel prototypes were fabricated and subjected to mK characterization. Four-wire resistance measurement results confirmed a 2/3 production yield against strict design targets (TC ~100 mK). Finally, functional testing at a bath temperature of 50 mK using a VTT FAB4 SQUID readout demonstrated excellent performance, including a low-energy threshold of ~0.6 keV, a pixel power dissipation of 5.15 nW, and an energy resolution ΔEFWHM = 735 eV at 6 keV. These combined achievements successfully validate the entire manufacturing and operational baseline against all primary space mission requirements. This paper has to be considered as a review of the CryoAC technology path toward the TRL5 achievement; main findings will be reported and discussed. Details are relegated to other papers.

On 2022 March 26, the ESA Solar Orbiter mission observed the early evolution of a coronal mass ejection (CME). On that day, the spacecraft was at a heliocentric distance of 0.32 au and a longitude separation from Earth of 74 . ° 5. The CME source region, observed with the Solar Orbiter Polarimetric and Helioseismic Imager magnetometer, shows no preexisting filament or flux rope. The event was first observed in the inner corona by the Solar Orbiter Extreme Ultraviolet Imager instrument with the Full Sun Imager telescope, showing the initial propagation of a flux rope seen face-on in the EUV, and formed during the eruption. Higher up, the event was observed by Metis with the Visible Light channel with an unprecedented time cadence of 20 s and a spatial resolution of 20” corresponding to about 4600 km bin −1 . The sequence of total brightness images shows the existence of small-scale circular flows inside the expanding flux rope, surrounded by multiple nested arch-shaped features. These motions, never reported so far, occur inside the void of the CME, with projected speed ∼40% higher than the CME propagation speed. The formation of the flux rope during the eruption suggests that these motions can be interpreted as a signature of conversion of magnetic writhe into twist, starting from the shearing of a preexisting arcade.

The Metis coronagraph onboard Solar Orbiter and the LASCO-C2 coronagraph onboard SoHO both acquire white light polarized brightness (pB) images of the solar corona. When the Sun–Solar Orbiter distance is less than 0.85 AU, i.e., outside orbital segments around aphelia, the range of elongations covered by the fields-of-view of the two instruments overlap significantly, allowing a quantitative comparison of their images. We report on such a comparison during September 2022, with images taken during a superior conjunction of the two spacecraft with the Sun, as well as close to that event. In each comparison, the two instruments observed the corona from opposite viewpoints, within ≈ 1^∘ in both Carrington longitude and latitude, with Metis at a distance of about half an astronomical unit from the Sun. We find that the Metis measurements are systematically larger than those of LASCO-C2 throughout the corona, with the Metis-to-C2 ratio of pB exhibiting a median value of ≈ 1.6 . The discrepancy is observed comparing essentially simultaneous observations, so it cannot be explained as an effect of coronal dynamics. Synthetic images of the solar corona computed from a stationary three-dimensional magneto-hydrodynamic model, replicating the geometry of the observations, are photometrically consistent. This rules out the small departure of the two instruments from observing from opposite viewpoints, or their different distance to the Sun, as the cause of their discrepant measurements. We conclude that the reported discrepancy has its root in the calibration methods of the two instruments, which should be further investigated.

The Athena mission entered a redefinition phase in July 2022, driven by the imperative to reduce the mission cost at completion for the European Space Agency below an acceptable target, while maintaining the flagship nature of its science return. This notably called for a complete redesign of the X-ray Integral Field Unit (X-IFU) cryogenic architecture towards a simpler active cooling chain. Passive cooling via successive radiative panels at spacecraft level is now used to provide a 50 K thermal environment to an X-IFU owned cryostat. 4.5 K cooling is achieved via a single remote active cryocooler unit, while a multi-stage Adiabatic Demagnetization Refrigerator ensures heat lift down to the 50 mK required by the detectors. Amidst these changes, the core concept of the readout chain remains robust, employing Transition Edge Sensor microcalorimeters and a SQUID-based Time-Division Multiplexing scheme. Noteworthy is the introduction of a slower pixel. This enables an increase in the multiplexing factor (from 34 to 48) without compromising the instrument energy resolution, hence keeping significant system margins to the new 4 eV resolution requirement. This allows reducing the number of channels by more than a factor two, and thus the resource demands on the system, while keeping a 4' field of view (compared to 5' before). In this article, we will give an overview of this new architecture, before detailing its anticipated performances. Finally, we will present the new X-IFU schedule, with its short term focus on demonstration activities towards a mission adoption in early 2027.

Metis, one of the instruments of the ESA mission Solar Orbiter (launched on February 10th, 2020, from Cape Canaveral), is a coronagraph with 2 channels, capable of performing broadband polarization imaging in the visible range (580-640 nm), and narrow-band imaging in UV (HI Lyman-alpha 121.6 nm). It is equipped with two detectors based on CMOS APS sensors: the visible channel includes a custom CMOS sensor with direct illumination, while the UV channel is provided with an intensified camera, based on a Star-1000 rad-hard CMOS APS coupled via a 2:1 fiber optic taper to a single-stage Microchannel Plate intensifier coated with an opaque KBr photocathode and sealed with an entrance MgF2 window. Dark subtraction is a crucial step in the data reduction pipeline, thus requiring careful in-flight monitoring and characterization of the dark signal. Since it is not possible to directly acquire dark images with the visible detector, as the door of the instrument is not light-tight, an ad hoc procedure has been designed to estimate the correction to be applied. In the case of the UV detector, however, it is possible to acquire dark frames by turning off the intensifier. Due to small fluctuations occurring on the bias signal level even on short timescales, an algorithm has been developed to correct the dark matrix frame by frame.

The ATHENA X-ray telescope will be the largest X-ray optics ever built. The ground calibration of this mirror assembly raises significant difficulties due to its unprecedented size, mass and focal length. The VERT-X project aims at developing an innovative calibration system which will be able to accomplish to this extremely challenging task.The design is based on an X-ray parallel beam produced by an X-ray source positioned in the focus of a highly performing X-ray collimator; the beam will be accurately moved by a raster-scan mechanism covering all the ATHENA optics at different off-axis angles. The main driving factor in the VERT-X design is the ATHENA calibration requirement on the accuracy in the HEW measure which is 0.1”, all over the field of view. The VERT-X project, started in January 2019, is financed by ESA and conducted by a consortium that includes INAF together with EIE, Media Lario, BCV Progetti and GPAP.

Microchannel plates-based detectors have been for a long time the detectors of choice for astronomical applications in the FUV/EUV, due to their photon counting capability and the possibility of solar blindness. In the framework of technological R&D for a future astronomical FUV/EUV spectrograph, we are developing a new readout system to allow unprecedented dynamic range. The goal is to realize a photon counting, solar blind, UV detector, based on a MCP read out with a 2D anode array integrated in a custom designed Read Out Integrated Circuit (MIRA - Microchannel plate Readout ASIC), able to reach unprecedented performance in terms of dynamic range combined with spatial resolution close to 30 mu m. Each pixel contains an anode to collect the electrons emitted by the MCP, a low noise amplifier and filter to maximize the SNR, a comparator to recognize and count single photon events, logic to correct for charge sharing among pixels (CSCL) and two counters. Some preliminary characterization of the first prototype, based on a demonstrator of the MIRA ASIC, 32x32 pixels, 35x35 mu m(2) size, for a total chip area of 2x2 mm(2), integrated into a standard demountable MCP intensifier, have been carried out.

We carried out tomographic reconstructions of the three-dimensional distribution of the electron density of the solar corona based on white light polarized brightness (pB) images taken by the Metis coronagraph on board the Solar Orbiter (SolO) mission. We selected three different time intervals during 2022, and further implemented independent synchronous reconstructions based on LASCO-C2 pB images for comparison purposes. The range of elongations covered by the field-of-view (FoV) of Metis considerably varies as SolO describes its highly eccentric orbit, whereas that of LASCO-C2 remains almost constant. During the selected time intervals, their FoVs partially overlap, allowing a comparison of the reconstructions within the regions in common. The shape and size of the reconstructed coronal structures, streamers and coronal holes, are consistent, demonstrating the suitability of the images of the synoptic program of Metis for tomographic reconstruction of the coronal electron density over its varying FoV. A comparison between the two tomographic reconstructions for each analyzed time interval, shows that the Metis-to-C2 ratio of reconstructed electron density has a median value of ≈ 1.7 . This is consistent with the observed ratio of the pB measurements of the two instruments. Our analysis thus also illustrates the value of tomography as a tool for intercalibrating solar coronagraphs irrespective of their spatial location, as long as their FoV partially overlap.

Spectroscopic observations in the far and extreme ultraviolet (FUV/EUV) spectral regions are of great interest in various scientific fields, such as solar physics, interstellar medium physics, and planetary exospheres studies. In this work, we present microchannel plate readout ASIC (MIRA), an application-specific integrated circuit (ASIC) to be coupled with a microchannel plate (MCP) as photons counting detectors for future UV spectrometers working in the 55-200-nm spectral range. The first prototype of MIRA features an MCP 2-D anode readout with a compact pixel size ( 35 x 35 mu m(2)) for a total of 32 x 32 pixels in a 2 x 2 mm(2) ASIC area. MIRA, designed in a 65-nm CMOS process, features two selectable analog processing times (130 or 260 ns), a count rate per pixel of 100 kcps and an equivalent noise charge (ENC) =20 e(-) , smaller than most photon-counting ASICs, to allow operations with lower MCP gains, to extend MCP lifetime for long missions in space. A charge sharing correction logic (CSCL) is implemented inside each pixel to grant a spatial resolution of 35 mu m, even in the case of charge sharing. In this article, the ASIC design is described and the results of its experimental characterization, also in a preliminary test with an MCP, are presented.

BEaTriX, which stands for Beam Expander Testing X-ray facility, is operated by the INAF-Brera Astronomical Observatory at its premises in Merate, Italy. It serves as ground support equipment for the verification phase of NewAthena, the upcoming L-class X-ray space observatory confirmed by ESA in November 2023 as a flagship mission. BEaTriX will conduct acceptance tests of the Silicon Pore Optics Mirror Modules (SPO MMs), which, when properly assembled, will form the X-ray grazing-incidence optics with a diameter of over 2 meters. The facility is compact (just 8 m x 14 m). Thanks to an innovative optical design based on an asymmetrical-cut crystal associated with a paraboloidal grazing incidence mirror, it can produce an expanded X-ray beam (170 mm x 60 mm) with low divergence (about 2 arcsec measured for the 4.51 keV beamline) at the two monochromatic energies of 4.51 keV and 1.49 keV. This allows us to calibrate each SPO MM's Effective Area and Point Spread Function precisely. The first beamline, at 4.51 keV photon energy, is already operational, as the commissioning was completed in Q1-2023. The second beamline, at 1.49 keV energy, is being developed. It presents some more challenging aspects from both the design and implementation points of view. The monochromator stage is based on two Quartz (100); two ADP asymmetric-cut crystals (101) will provide the horizontal expansion of the beam. The X-ray source needs to be very brilliant (5 x 10(11) - 10(12) ph/s/sterad) due to the large fraction of photons rejected by the crystals. This paper describes the ongoing activities. It will present the results of the 4.51 keV X-ray beamline optimization and the tests performed on a coated MM. It will also describe the progress in implementing the 1.49 keV components and discuss the comparison with other X-ray testing facilities.

The ASTRI Mini-Array is a collaborative international effort led by the Italian National Institute for Astrophysics (INAF) to develop, build and operate a facility of nine Imaging Atmospheric Cherenkov Telescopes of the four meters class to study astronomical sources emitting very high energy gamma-rays in the TeV spectral band. The ASTRI Mini-Array is currently under construction on the island of Tenerife at the Observatorio del Teide based on a host agreement with the Instituto de Astrofisica de Canarias. The telescopes are alt-azimuthal with an innovative aplanatic dual mirror optical configuration. The first telescope of the ASTRI Mini-Array, named ASTRI-1, was installed at the end of summer 2022. In this paper we report on the results of the opto-mechanical characterization of the telescope. In particular, we analyzed the mechanical behavior of the telescope and we measured the pointing and tracking performance that resulted within the requirements. We tested the procedure to align and focus the panels of the primary mirror automatically. All the software procedures to run the telescope and perform these analyses were also tested.

Context. The Solar Orbiter Metis coronagraph captures images of the solar corona in both visible (VL) and ultraviolet (UV) light. Tracks ascribable to the passage of galactic and solar particles appear in the Metis images. An algorithm implemented in the Metis processing electronics allows us to separate the pixels fired by VL photons from those crossed by high-energy particles. These spurious pixels are stored in cosmic-ray matrices that can be visually analyzed for particle monitoring deep into the spacecraft’s interior. This algorithm has been enabled for the VL instrument only, since the process of separating the particle tracks from pixels fired by photons in the UV images was shown to be quite challenging with respect to a quantitative analysis. Aims. This work is aimed at studying galactic cosmic rays (GCRs) and solar energetic particles (SEPs) with the Metis cosmic-ray matrices in February 2023. Methods. We compared a visual analysis of Metis cosmic-ray matrices gathered on February 22, 2023, with GCRs only, and on February 25, 2023 with both GCRs and SEPs, to Monte Carlo simulations of the VL instrument during the same days. Results. We estimated the solar modulation parameter associated with the GCR proton energy spectrum in February 2023. We show that Metis plays the role of monitoring galactic and solar protons. The Metis particle observations are used for the diagnostics of the VL instrument performance and to study the spacecraft inner charging from solar minimum towards the next solar maximum. These achievements have been attained with the benefit of the joint observations of Metis, the Energetic Particle Detector/High Energy Telescope, and near-Earth and Earth-based instruments.

Context. Ultraviolet (UV) emission from coronal mass ejections can provide information on the evolution of plasma dynamics, temperature, and elemental composition, as demonstrated by the UV Coronagraph Spectrometer (UVCS) on board the SOlar and Heliospheric Observatory (SOHO). Metis, the coronagraph on board Solar Orbiter, provides for the first time coronagraphic imaging in the UV H I Ly- α line and, simultaneously, in polarized visible light, thus providing a host of information on the properties of coronal mass ejections and solar eruptions such as their overall dynamics, time evolution, mass content, and outflow propagation velocity in the expanding corona. Aims. For this work, we analyzed six coronal mass ejections observed by Metis between April and October 2021, which are characterized by a very strong H I Ly- α emission. We studied in particular the morphology, kinematics, and the temporal and radial evolution of the emission of such events, focusing on the brightest UV features. Methods. The kinematics of the eruptive events under consideration were studied by determining the height-time profiles of the brightest parts on the Metis plane of the sky. Furthermore, the 3D positions in the heliosphere of the coronal mass ejections were determined by employing co-temporal images, when available, from two other coronagraphs: LASCO/C2 on board SOHO, and COR2 on board STEREO-A. In three cases, the most likely source region on the solar surface could be identified. Finally, the radiometrically calibrated Metis images of the bright UV features were analyzed to provide estimates of their volume and density. From the kinematics and radiometric analysis, we obtained indications of the temperatures of the bright UV cores of these events. These results were then compared with previous studies with the UVCS spectrocoronagraph. Results. The analysis of these strong UV-emitting features associated with coronal mass ejections demonstrates the capabilities of the current constellation of space coronagraphs, Metis, LASCO/C2, and COR2, in providing a complete characterization of the structure and dynamics of eruptive events in their propagation phase from their inception up to several solar radii. Furthermore, we show how the unique capabilities of the Metis instrument to observe these events in both the H I Ly- α line and polarized VL radiation allow plasma diagnostics on the thermal state of these events.

This Letter reports the first observation of the onset of fully developed turbulence in the solar corona. Long time series of white-light coronal images, acquired by Metis aboard Solar Orbiter at 2 minutes cadence and spanning about 10 hr, were studied to gain insight into the statistical properties of fluctuations in the density of the coronal plasma in the time domain. From pixel-by-pixel spectral frequency analysis in the whole Metis field of view, the scaling exponents of plasma fluctuations were derived. The results show that, over timescales ranging from 1 to 10 hr and corresponding to the photospheric mesogranulation-driven dynamics, the density spectra become shallower moving away from the Sun, resembling a Kolmogorov-like spectrum at 3 R circle dot. According to the latest observation and interpretive work, the observed 5/3 scaling law for density fluctuations is indicative of the onset of fully developed turbulence in the corona. Metis observation-based evidence for a Kolmogorov turbulent form of the fluctuating density spectrum casts light on the evolution of 2D turbulence in the early stages of its upward transport from the low corona.

On 2021 September 28, a C1.6 class flare occurred in active region NOAA 12871, located approximately at 27°S and 51°W on the solar disk with respect to Earth’s point of view. This event was followed by a partial halo coronal mass ejection (CME) that caused the deflection of preexisting coronal streamer structures, as observed in visible-light coronagraphic images. An associated type II radio burst was also detected by both space- and ground-based instruments, indicating the presence of a coronal shock propagating into interplanetary space. By using H i Ly α (121.6 nm) observations from the Metis coronagraph on board the Solar Orbiter mission, we demonstrate for the first time the capability of UV imaging to provide, via a Doppler dimming technique, an upper limit estimate of the evolution of the 2D proton kinetic temperature in the CME-driven shock sheath as it passes through the field of view of the instrument. Our results suggest that over the 22 minutes of observations, the shock propagated with a speed decreasing from about 740 ± 110 km s ^−1 to 400 ± 60 km s ^−1 . At the same time, the postshock proton temperatures peaked at latitudes around the shock nose and decreased with time from about 6.8 ± 1.01 MK to 3.1 ± 0.47 MK. The application of the Rankine–Hugoniot jump conditions demonstrates that these temperatures are higher by a factor of about 2–5 than those expected from simple adiabatic compression, implying that significant shock heating is still going on at these distances.