NASA’s ambitious plan of imaging 25 Earth-like planets with its future Habitable Worlds Observatory requires a coronagraph that can reach a contrast on the order of 10−10 across a broad band. One of the most promising architectures to achieve this goal is a vortex coronagraph, providing a good tradeoff between small inner working angle and high throughput, as well as low sensitivity to low-order aberrations. Current vortex coronagraphs are of vectorial nature and have shown promising results so far; however, they imprint opposite phase ramps on the two circular polarizations making wavefront control in both polarizations simultaneously challenging. An alternative to the vector vortex is the polarization-independent scalar vortex coronagraph, which imprints the same phase ramp regardless of polarization. Current scalar vortex phase mask implementations are however limited by their chromaticity. We present designs for a scalar vortex phase mask combined with a phase grating. We show that this architecture is capable of spatially separating the chromatic leakage from the vortex beam and present simulation results of this concept. We then discuss different implementations based on both shaped dielectric masks and metasurfaces. Finally, we discuss potential manufacturing approaches to fabricate the forked grating scalar vortex phase mask and their feasibility.
We present AAVS3, the latest prototype station of the SKA-Low Aperture Array Verification System, and its role in mitigating design risks for the SKA-Low telescope. AAVS3 replaces the pseudo-random AAVS2 layout with the Vogel “sunflower” pattern to improve spatial uniformity and azimuthal diversity. Interferometric visibility calibration procedures were developed using CASA, including a basic Sun-based method and an advanced technique combining embedded element patterns with the global sky model. Electromagnetic simulations conducted during construction predicted a sensitivity depression near zenith at 125 MHz due to geometric regularities inherent in the Vogel layout, and on-sky measurements confirmed this behavior. The Vogel layout was therefore not adopted for the SKA-Low array. The calibration methods and measurements presented here provide technical guidance for SKA-Low prototyping and inform commissioning activities for the first SKA-Low stations.
Telescope-drive systems are a critical but underdiscussed foundation of astronomical performance because they determine whether commanded motion can be converted into stable pointing, smooth tracking, and long-duration operational availability. This challenge is becoming more acute in next-generation observatories, where direct-drive architectures, extreme environmental exposure, sparse fault data, and restricted maintenance access make conventional reliability assumptions increasingly inadequate. We synthesize the emerging literature on intelligent operation and maintenance (O&M) for telescope-drive systems, with particular emphasis on extreme-environment and unattended scenarios, and organize the field across five linked stages: state perception, fault diagnosis, behavior prediction, safety protection, and intelligent decision-making. We argue that digital twin provides the most coherent architecture for binding these stages into a closed-loop health-management framework; reframe telescope-drive reliability as a telescope-systems problem spanning sensing, control, degradation, and operational decision; place the unanticipated state at the center of telescope intelligent O&M; and evaluate current astronomical evidence across representative observatories and telescope projects. The main conclusion is that near-term progress depends on telescope-specific unanticipated-state definitions, condition-aware twins validated against laboratory and field evidence, sparse-data diagnosis that preserves uncertainty, and graded protection and decision logic suited to remote observatory operation.
The THz range has been under-explored for solar astronomy, mainly due to technological limitations. Only recently, a few new telescopes, such as the High Altitude Terahertz Solar (HATS) photometer, have been monitoring the solar activity in this range of the spectrum. This paper presents the experimental characterization and voltage-to-temperature calibration of the HATS acquisition system. HATS uses a Golay cell for capturing the incoming radiation, modulated by a 20 Hz fork chopper. The amplitude of the signal is then obtained at predetermined time intervals by applying a windowing function and an FFT to the signal. To characterize this acquisition system, a blackbody calibrator, with temperatures varying from 100 to 500 C (373.15 K to 648.15 K), was used as a THz source, and two signal recovery methodologies were compared: sinusoidal curve fitting and FFT combined with six windowing functions (rectangular, Hamming, Hann, Barlett, Blackman, and Flat Top). Our quantitative results demonstrate high linearity in the system's response over the input source's temperature range, with the Hamming window achieving the highest precision, yielding a Root Mean Square Error (RMSE) of 15.48 and a calibration temperature-to-voltage factor of 10.32 +- 0.13 mV/K. In contrast, the Bartlett window presented the highest error (RMSE 16.02). The choice of windowing function had only a minor effect on the calibration factors, which ranged from 10.32 to 10.43 mV/K, all within the experimental uncertainties. Beyond solar photometry, the signal modulation and windowing concepts established here are highly applicable to other fields requiring high-sensitivity thermal detection, such as industrial pyrometry for high-temperature manufacturing, environmental monitoring of atmospheric water vapor, and the development of medical imaging systems based on Terahertz radiation for non-invasive tissue analysis.
The development of large-scale superconducting transition-edge sensor arrays for missions such as the Diffuse X-ray Explorer and the Hot Universe Baryon Surveyor is bottlenecked by the time-consuming cryogenic characterization of inductor-capacitor (LC) filters in the frequency-division multiplexing readout. We developed a rapid screening test system based on a liquid helium environment (4.2K), with the core being the self-developed High-Throughput Low-Temperature Probe (HT-Dipstick). The probe is made of G-10 composite material as the main structure, ensuring mechanical and thermal reliability for repeated operation in ultranarrow bore dewars and enabling parallel S-21 parameter measurements of a 40-channel LC filter array within a single cooldown cycle, reducing the average testing time per array from several hours to about 20 min. By accurately fitting the resonance curves, the system reliably extracts the resonance frequency and quality factor of each channel, effectively distinguishing high-performance devices from defective ones. Compared with traditional cryocooler testing, this solution improves screening efficiency by nearly 2 orders of magnitude, providing a feasible engineering solution for the rapid construction of large-scale readout arrays, and has a clear path for integration with future liquid helium recycling technologies to reduce costs and enhance efficiency.
X-ray interferometry (XRI) is a promising technique for ultra-high resolution X-ray imaging. However, a major limitation of a regular design is the long length of the interferometer, which makes it virtually impossible to fit in a single spacecraft. The Willingale XRI design reduced the length by several orders of magnitude with the introduction of a slatted mirror. We propose to parallelize the interferometer using silicon pore optics (SPO). We show that SPO technology, currently being used to fabricate mirrors for ESA's upcoming NewAthena space mission, can be used for XRI and benefit by starting at a higher technology readiness level. We provide a detailed design description of Willingale XRI and combine it with SPO along with an optimization approach. Further, we apply the optimization approach for a Willingale's XRI testbed. The optimized design is checked with a ray optics simulation. Furthermore, we report successful fabrication of a slatted mirror manufacturing prototype. The optimized design and fabrication of a slatted mirror manufacturing prototype will serve as a first step toward building an XRI testbed for the demonstration of X-ray interference fringes that would demonstrate the feasibility of a Willingale type XRI.
Cross-dispersed echelle spectrographs (CDESs) are a fundamental tool for modern astronomy. The spectral resolution achieved by these instruments is directly related to the size of the echelle grating and the focal length of the collimator. However, when they are used in ground-based observatories, they are typically seeing-limited, meaning that the achievable spectral resolving power is limited by the coherent fraction of the telescope aperture. As a result, achieving high-spectral resolution requires large echelle apertures and long collimator focal lengths, leading to instruments with significant dimensions. These dimensions are often also necessary to ensure the thermal and mechanical stability required by demanding science cases. With the advent of large-aperture telescopes and the unrelenting demand for high resolution, the prevailing trajectory of these instruments leans toward escalating in both size and complexity. However, it is important to explore miniaturization strategies for CDESs, which are particularly valuable, for example, for space-based instruments where size, weight, and power are crucial. In addition, space-based observatories are not affected by atmospheric seeing and can therefore operate in a diffraction-limited regime, allowing the full grating-limited spectral resolution to be exploited. In this work, we demonstrate the working principle of a parametric model that describes two configurations of CDES: the Three-fold (3F) and the Cassegrain (CA) design. The Three-fold CDES is a white-pupil design that is currently used at major observatories, and it is based on a single parabolic mirror for collimation and folding of the optical path. The Cassegrain CDES, a white-pupil design with a novel approach to the collimator, uses an inverted Cassegrain telescope design as a telephoto collimator. This allows for the design to achieve the same collimator focal length as with a single parabolic mirror but in a smaller footprint, paving the way for a possible miniaturization strategy for the 3F design. The presented model evaluates both configurations using two merit figures: the spectral resolving power and the design dimensions without the need to use conventional graphical ray-tracing software. This is used to systematically explore the design space of both configurations. Using Zemax simulations, we validate the model outputs in terms of spectral resolving power and instrument dimensions.
We present a fast and robust algorithm for star identification, designed to associate detected sources in astronomical images with reference stars from high-precision stellar catalogs. The method constructs and matches star pairs using geometric and photometric invariants-pairwise distance, relative orientation, and brightness ratio-to achieve both efficiency and accuracy. By selecting only the brightest stars from the image and the catalog, the algorithm substantially reduces combinatorial complexity compared with traditional triangle-based approaches. Star-pair invariants are matched within defined tolerances, followed by angular voting to estimate global rotation. A four-parameter affine transformation is then derived through least-squares fitting on the tangent plane, and an iterative sigma-clipping scheme removes outliers for robust refinement. Experimental results based on real and simulated CCD images from the 1 m telescope at Yunnan Observatories demonstrate that the proposed algorithm achieves millisecond-level matching speed while maintaining high reliability. The method shows strong resilience to positional errors, false detections, and missing stars, making it suitable for automated astrometric calibration and spacecraft attitude determination in modern imaging pipelines.
The Habitable Worlds Observatory (HWO), NASA’s next flagship science mission, follows in the tradition of the Nancy Grace Roman Space Telescope (Roman) and other preceding great observatories. HWO will directly image and characterize Earth-like exoplanets and their atmospheres, with the capability to detect biosignatures and potentially answer the question “are we alone?” HWO will also serve as a powerful general astrophysics observatory, enabling breakthroughs in galaxy evolution, stellar astrophysics, and dark matter studies. Currently in preformulation, the project has established Exploratory Analytic Cases (EACs), a series of architectural concept designs used to assess the mission’s demanding science objectives while exploring challenging engineering parameters. We describe the first three EACs, starting with observing strategies and error budget formulation and then progressing to design formulations, trade studies, and lessons learned; we also discuss the integrated modeling pipeline, a key multidisciplinary system-level analysis capability, and analysis findings as applied to the first EAC. These activities set the stage for the follow-on EACs 4 and 5, which will further explore the trade space and prepare for the baseline design that will support the Mission Concept Review (MCR).
In astronomical fiber-fed spectroscopic surveys, misalignment between optical fibers and stellar image spots, together with CCD noise, can produce uneven or annular spot patterns, leading to reduced coupling efficiency and degraded spectral accuracy. Because spectroscopic imaging systems generally lack dedicated instrumentation to monitor the fiber output spot in situ, the coupling performance cannot be directly assessed during routine observations. We present a two-dimensional spot energy reconstruction method that combines neural-network-based pixel-level noise segmentation with dynamic background modeling. The proposed approach enables recovery of a physically consistent two-dimensional spot morphology directly from science data, without requiring additional observations or hardware modifications. Meanwhile, spot-like noise artifacts in fiber spectral images are identified and labeled, preventing erroneous information from being introduced into the reconstruction and providing objective criteria for potential re-observation of affected targets. Validation using real data from LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) demonstrates that the method effectively suppresses background noise, identifies spot-related noise artifacts, and quantitatively evaluates the fiber-spot coupling quality. When integrated with artificial intelligence modules, the proposed framework offers a practical solution for real-time fiber-coupling diagnostics and spectral-quality assessment, enabling rapid processing and feedback for large-scale spectroscopic surveys.
Microwave kinetic inductance detectors (MKIDs) remain a strong contender for use in UVOIR-band astronomy due to their straightforward scalability. Improvements to yield, throughput, and resolving power are still required for MKIDs to be the premier candidate for use in future missions such as the Habitable Worlds Observatory. We describe a recent array that improves upon the internal quality factors, yield, and throughput of the array used in the MKID exoplanet camera (MEC) at the Subaru Telescope. The array was fabricated with β-Ta resonators, Nb groundplanes, and Al airbridge crossovers. Resonator internal quality factors, Qis, were doubled compared with the MEC array, increasing from a median of 1.07×105 to a median of 2.17×105. Resonator yield was increased to 88%, with 100% feedline yield. Array quantum efficiency was improved to 89±2% at 500 nm, with resonators varying with a standard deviation of 18%. The high disorder and high kinetic inductance (95 pH/□) of this β-Ta led to increased current density in the capacitor rails (i.e., parasitic inductance) and low quasiparticle lifetimes. This increased its maximum count rate at the cost of decreased responsivity, making the array more compatible with photon-counting applications such as photonic quantum computing and limited for astronomical spectroscopy.
Submillimeter astronomy offers a fundamental window into the obscured Universe. However, there are very few submillimeter sites in the eastern hemisphere. Developing and deploying a submillimeter telescope in a high-altitude site in China and in Antarctica could be challenging but promising. We present the control system, operation, and site monitoring of a new portable sub-millimeter telescope-the 60-cm Antarctic Terahertz Explorer (ATE60) telescope-developed by the Millimeter and Submillimeter Laboratory of the Purple Mountain Observatory. The ATE60 telescope has been successfully deployed to the 4820-m height Xueshanmuchang (XSMC) site in the Qinghai-Tibet Plateau of China, and the 4020-m height Dome A site in Antarctica. The telescope is equipped with dual-band (500 and 800 GHz) 5 K superconducting heterodyne receivers and incorporates several features: (i) an optical/near-IR guide-star tracking system, (ii) a dynamic pointing calibration and observation queuing system, and (iii) a dual-band capability, combined with skydip, position-switching (PS), and on-the-fly (OTF) observing modes. Some features and techniques may be different from current large, fixed-site submillimeter telescopes and require further development. We describe the ATE60's control system, recent observational runs, and site monitoring results. We show that ATE60 achieves good pointing accuracy, and astronomical observations of NGC 6334I from Dome A and the Orion nebula from XSMC yielded high signal-to-noise (S/N) spectral line detections and reasonable line maps. Furthermore, skydip data show that the daily-median atmospheric opacity (tau) at XSMC can be as low as similar to 0.54 at 462 GHz between March 9 and 14, 2024. We indicate that XMSC is a pontentially excellent submillimeter site, and with more on-site monitoring in the near future, it could provide strong support for the construction of a new 15-m submm telescope (XSMT-15 m) there. This work also serves as the technical foundation for at least two 1-m ATE telescopes under construction, aiming at pioneer > 1 THz interferometry experiments and astronomical observations at XSMC and Dome A.
We describe a technique for spectrograph stabilization useful when conventional mitigation techniques of vacuum tanks, thermal insulation, and laser frequency comb may be impractical, expensive, heavy, or bulky. This includes spectrographs on airborne platforms or mounted on telescopes where they suffer a changing gravity vector or other drifts. Placing a fixed-delay interferometer in series with a spectrograph forms an externally dispersed interferometer (EDI). This produces a uniform sinusoidal comb multiplying input spectrum, creating (through heterodyning) beats (moir & eacute; patterns). In Fourier space for low frequencies up to the comb frequency, the moir & eacute; generated signal counter-rotates to ordinary spectra under an unknown disperser wavenumber drift Delta x. This generates a large negative feedback signal useful in a conceptual control loop, to converge rapidly to a stable spectrum and yield Delta x. A modified EDI data analysis algorithm ("crossfading") combines frequency-weighted moir & eacute; with conventional spectrum to cancel net output spectrum reaction to Delta x. Needing only a single-delay, this is a practical improvement over prior crossfading analyses requiring multiple delays. We test crossfading on ThAr data near 4850 cm(-1) taken on Hale telescope in an earlier project. In a single pass, we reduce drift 20 times. Using seven iterations, we reduce 0.5 cm(-1) (31 km/s Doppler equivalent) drift to 4 & times;10(-7) cm(-1) (2.5 cm/s). The interferometer delay can wander, because linearity of phase versus wavenumber interpolates science features between bracketing calibrating spectral references. Second, mathematically reversing the heterodyning effect doubles effective spectral resolution without changing disperser slit.
Missions and instruments capable of identifying high-redshift gamma-ray bursts (GRBs) can increase the sample of z>5 GRBs and improve our understanding of the early Universe. Obtaining rapid redshift estimates is key for identifying GRBs for follow-up observations, with photometric redshifts being a powerful method. However, low-redshift GRBs with high extinction can mimic the signature of a high-redshift GRB when using broad photometric bands. Understanding how the design of photometers impacts redshift estimation performance is important for designing instruments for high-redshift GRB missions. We adapt a photometric redshift performance estimation software package to compare the performance of different photometric band configurations with varying numbers of photometric bands and different wavelength coverage. We show that although increasing the number of photometric bands can improve redshift estimation for GRBs at the highest redshifts, extending the wavelength coverage of photometric instruments is the most effective way to improve redshift estimation performance over a broader redshift range. We also implement a more physically accurate model to assess its impact on redshift retrieval but find that the model does not have a significant impact on the redshift estimation performance.
The Rockets for Extended-Source X-ray Spectroscopy (tREXS) suborbital rocket mission was designed to demonstrate medium-resolution (R approximate to 50) soft-X-ray spectroscopy of diffuse astrophysical sources such as supernova remnants. A critical component of the payload is the focal-plane camera, a large-area mosaic of eleven back-illuminated Teledyne-e2v CIS113 ("Vega") CMOS image sensors. The Vega devices were selected for their large format, low noise, three-side buttable packaging, and demonstrated ruggedness for suborbital environments. Together, the array provides a contiguous similar to 97-megapixel focal plane with more than 250 cm(2) of active silicon, enabling coverage of the line-spread function produced by the tREXS spectrograph and simultaneous capture of multiple dispersed spectral orders. This paper describes the design, integration, and performance of the tREXS focal-plane camera. The mechanical and thermal architecture, including vacuum compatibility and liquid nitrogen-based cooling, as well as the custom readout-electronics chain developed to support the multidetector system are reviewed. Pre-flight calibrations established detector gain, readout noise, and energy resolution, whereas post-flight data provide insight into detector behavior under launch and space operating conditions. Particular challenges such as persistence, low-DN Fe55 events, and electromagnetic interference are discussed, along with mitigation strategies implemented in the design. Despite an ice contamination event just prior to launch, the camera demonstrated performance consistent with what is required for mission success, despite readout noise above the initial requirements. This performance validated the feasibility of large-format tiled CMOS focal planes for suborbital X-ray spectroscopy. Lessons learned from this first flight inform future upgrades and re-flight opportunities for tREXS and similar missions.
