Space Detection Research Articles

A robust feature-based full-field initial value estimation in path-independent digital image correlation for large deformation measurement

The feature-based path-independent digital image correlation (DIC) method has been shown to be a formidable tool for non-contact, full-field measurement of large deformation, but its effectiveness hinges crucially on acquiring sufficient matched features to perform a reliable full-field initial value estimation (IVE) for all points of interest (POIs), thus ensuring their successful and rapid convergence in the succeeding path-independent iterative DIC refinement. This prerequisite is a challenging task particularly when confronted with large deformation. Moreover, in many real-world measurement scenarios, the accuracy of IVE is also influenced by image noise, such as Gaussian noise and shot noise, further compounding the challenge. To mitigate these issues, we propose a robust feature-based full-field IVE method. The core of this method consists of two main components: (i) For feature detection, we leverage the strengths of nonlinear multiscale representations on speckle images using an Accelerated-KAZE (A-KAZE) detector, which extracts features in a nonlinear scale space via nonlinear diffusion filtering. Noise is suppressed and edges are preserved. Compared to existing state-of-the-art feature detectors used in DIC, such as Scale Invariant Feature Transform (SIFT) and Speeded-Up Robust Feature (SURF) detectors, which rely on the use of Gaussian linear scale spaces, the A-KAZE-based nonlinear scale space detector identifies more salient features with higher localization accuracy. (ii) For feature description, considering the need for robustness against large deformation and the computational burden of descriptor matching for considerable salient features that may be detected in speckle images, we introduce a robust Gradient Location and Orientation Histogram (GLOH) descriptor and propose an improved version of it. The GLOH's improved version incorporates a restricted adaptive binning (RAB) strategy to optimize the descriptor’s structure parameters, which is able to reduce the computational cost of descriptor matching through restricting its dimensionality while without sacrificing its robustness and discriminability. These two components are designed to provide sufficient matched features for a full-field IVE. The initial deformation for each POI is estimated independently by fitting a local affine transformation model, which is refined to subpixel accuracy through iterative path-independent DIC analysis. To handle complex large deformation, the inverse compositional Gauss-Newton (IC-GN) algorithm with a second-order shape function is employed. Extensive experimental results demonstrate that our method has improved IVE accuracy as well as behaves more robustness against local geometric transformations and image noise including Gaussian noise and shot noise, as compared to existing state-of-the-art feature-based full-field IVE methods.

Experimental end-to-end demonstration of intersatellite absolute ranging for the Laser Interferometer Space Antenna

The Laser Interferometer Space Antenna (LISA) is a gravitational wave detector in space. It relies on a postprocessing technique named time-delay interferometry to suppress the overwhelming laser frequency noise by several orders of magnitude. This algorithm requires intersatellite-ranging monitors to provide information on spacecraft separations. To fulfill this requirement, we use on-ground observatories, optical sideband-sideband beatnotes, pseudorandom noise ranging (PRNR), and time-delay interferometric ranging (TDIR). This article reports on the experimental end-to-end demonstration of a hexagonal optical testbed used to extract absolute ranges via the optical sidebands, PRNR, and TDIR. These were applied for clock synchronization of optical beatnote signals sampled at independent phasemeters. We set up two possible PRNR processing schemes: Scheme 1 extracts pseudoranges from PRNR via a calibration relying on TDIR; Scheme 2 synchronizes all beatnote signals without TDIR calibration. The schemes rely on newly implemented monitors of local-PRNR biases. After the necessary PRNR treatments (unwrapping, ambiguity resolution, bias correction, in-band jitter reduction, and/or calibration), Schemes 1 and 2 achieved ranging accuracies of 2.0–8.1 cm and 5.8–41.1 cm, respectively, below the classical 1-m mark with margins. Published by the American Physical Society 2024

The thermal performance model of a 105 mW@4.41 K 4He Joule-Thomson cryocooler designed for space applications

The 4He Joule-Thomson cryocooler (JTC) ensures the operation of space detectors working within the 4 K temperature range, such as the Block Impurity Band Infrared Detector (BIBID). In addition, the 4He JTC is one of the essential components of the 300 K to 50 mK space cryochain. It can precool sub-Kelvin refrigerators, such as the adiabatic demagnetization refrigerator (ADR) and the dilution refrigerator (DR). With the development of space science, the need for cooling power at the 4 K temperature range is growing. Thus, a thermal performance model of the 4He JTC precooled by a two-stage thermally coupled pulse tube cryocooler (PTC) is designed, manufactured, and tested with an eye toward space applications. A four-stage compression system with a high operating frequency and large pistons is designed and used to drive the JT cycle. This 4He JTC has a total mass of 55 kg and can provide a cooling capacity of 105 mW at 4.41 K with a total input electric power of 548 W.

An end-to-end calibration of the Mini-EUSO detector in space

Mini-EUSO is a wide Field-of-View (44∘×44∘) telescope currently in operation from a nadir-facing Ultra-Violet (UV) transparent window in the Russian Zvezda module on the International Space Station (ISS). Mini-EUSO has been designed as a scaled-down version of the original JEM-EUSO telescope to raise its instrumentation’s technological readiness level and demonstrate its observational principle, while performing multidisciplinary studies on different fields such as atmospheric science and planetology. One of Mini-EUSO main goals is the study of the UV background for future space missions employing the same concept as the original JEM-EUSO telescope, which requires an absolute calibration of the Mini-EUSO instrument. During the past years, a few observational campaigns have been completed, employing a ground-based UV flasher to perform an end-to-end calibration of the instrument. In this paper, we present the assembled UV flasher system, the operation of the field campaign and the analysis of the obtained data. The results are interpreted by the means of a parametrization of the Mini-EUSO photon counts. The end-to-end efficiency of several pixels has been obtained, taking into account different parameters such as the atmospheric attenuation, the optics efficiency and the multi-anode photomultiplier detection efficiency.

Design and application of a shipborne underwater radiation detector array for the monitoring of seawater radioactivity

A navigable online monitoring system for marine radioactivity was developed to cope with possible large-scale marine nuclear pollution incidents. This system used a NaI(Tl) detector array mounted on a ship to collect radioactive data across wide marine areas rapidly. High volume-efficiency aids the system in rapidly identifying radionuclides exceeding standard levels. This feature enables the system to monitor the seawater in a wide area within a shorter time and promptly detect marine nuclear pollution incidents. Monte Carlo simulations were used to optimize the number of NaI(Tl) crystals and the detector spacing for enhancing the volume-efficiency of the system. Three Φ3" × 6″ NaI(Tl) detectors and the mounting bracket with a fixed detector spacing of 30 cm were fabricated based on the simulation outcomes. The volume-efficiency for 137Cs of the system was around six times higher than that for the buoy-based monitoring system with a 3-inch NaI(Tl) detector. The theoretical volume-efficiency curve, which was calculated through Monte Carlo simulation, was verified in a standard liquid source. The minimum detectable activity concentration (MDC) for radioisotopes of the system under various radioactive measurement durations was discussed, such as the MDC for 137Cs for 5 min measurement was 0.152 Bq/L. Marine radioactivity measurement experiments were conducted in the sea near the Tianwan nuclear power plant in Lianyungang, China. The test results showed that the activity concentration of 40K was 11.4 Bq/L. The results of navigation monitoring were consistent with those of sampling and laboratory measurement, which verified the stability and accuracy of the system.

A mission planning method for deep space detectors using deep reinforcement learning

Mission planning for deep space detectors is a pivotal step in the successful execution of detection missions. Traditional planning approaches, which typically compartmentalize mission planning and data transmission scheduling, exhibit limitations in adapting to uncertainties and are often inadequate in responding to unforeseen opportunity targets. This paper introduces a mission planning method for deep space detectors designed to address these challenges. Firstly, a Markov Decision Process (MDP) model is formulated, integrating mission planning and data transmission scheduling, with a consideration for planning balance between detection missions and opportunity targets. Subsequently, a Planning Balance with Proximal Policy Optimization (PB-PPO) algorithm is proposed. The proposed algorithm, based in the Proximal Policy Optimization (PPO) algorithm, integrates an orthogonal initialization algorithm to afford improved control over parameter updates. Furthermore, a dynamic learning rate strategy is implemented to accelerate convergence speed. Experimental results show that, the PB-PPO achieves rewards that are 4.42%, 6.78%, 18.32%, and 26.81% higher than those obtained by compared algorithms. Additionally, the PB-PPO demonstrates the capability to address the planning balance between detection missions and opportunity targets, ensuring stable reward growth even when planning a significant number of opportunity targets. In summary, the PB-PPO integrates of MDP, deep reinforcement learning, and innovative strategies to make it a robust solution for detector mission planning in the complex and dynamic environment of deep space.

Wide Dynamic Range, High Uniformity Spectral Irradiance Source for Calibration of Scientific-Grade, Large-Size Space Detectors

In order to meet the high uniformity calibration requirements for scientific-grade, large-size space detectors used in the CHES Extrasolar Planet Exploration Mission, this paper presents the design of a wide dynamic range, high uniformity spectral irradiance source (WHUIS). Utilizing a cascade integrating sphere design, and optimizing the overlapping area radiant flux adjustment structure and illumination light path, we achieve a wide dynamic range and high uniformity irradiance output. We established an irradiance transmission model based on the new assumption and analyzed the influence of factors such as illumination distance, stray light, and non-uniform radiance on the uniformity of irradiance output. The model is then validated by building experimental equipment. The findings show that in a circular area of 40 mm, the irradiance uniformity of our light source system exceeds 99.9%, and constant color temperature is adjustable within six orders of magnitude, consistent with the uniformity level predicted by the model.

Virtual cylindrical PET for efficient DOI image reconstruction with sub-millimetre resolution

Objective. Image reconstruction in high resolution, narrow bore PET scanners with depth of interaction (DOI) capability presents a substantial computational challenge due to the very high sampling in detector and image space. The aim of this study is to evaluate the use of a virtual cylinder in reducing the number of lines of response (LOR) for DOI-based reconstruction in high resolution PET systems while maintaining uniform sub-millimetre spatial resolution. Approach. Virtual geometry was investigated using the awake animal mousePET as a high resolution test case. Using GEANT4 Application for Tomographic Emission (GATE), we simulated the physical scanner and three virtual cylinder implementations with detector size 0.74 mm, 0.47 mm and 0.36 mm (vPET1, vPET2 and vPET3, respectively). The virtual cylinder condenses physical LORs stemming from various crystal pairs and DOI combinations, and which intersect a single virtual detector pair, into a single virtual LOR. Quantitative comparisons of the point spread function (PSF) at various positions within the field of view (FOV) were compared for reconstructions based on the vPET implementations and the physical scanner. We also assessed the impact of the anisotropic PSFs by reconstructing images of a micro Derenzo phantom. Main results. All virtual cylinder implementations achieved LOR data compression of at least 50% for DOI PET reconstruction. PSF anisotropy in radial and tangential profiles was chiefly influenced by DOI resolution and only marginally by virtual detector size. Spatial degradation introduced by virtual cylinders was most prominent in the axial profile. All virtual cylinders achieved sub-millimetre volumetric resolution across the FOV when 6-bin DOI reconstructions (3.3 mm DOI resolution) were performed. Using vPET2 with 6 DOI bins yielded nearly identical reconstructions to the non-virtual case in the transaxial plane, with an LOR compression factor of 86%. Resolution modelling significantly reduced the effects of the asymmetric PSF arising from the non-cylindrical geometry of mousePET. Significance. Narrow bore and high resolution PET scanners require detectors with DOI capability, leading to computationally demanding reconstructions due to the large number of LORs. In this study, we show that DOI PET reconstruction with 50%–86% LOR compression is possible using virtual cylinders while maintaining sub-millimetre spatial resolution throughout the FOV. The methodology and analysis can be extended to other scanners with DOI capability intended for high resolution PET imaging.

The unresolved mystery of dust particle swarms within the magnetosphere.

Early-generation in situ dust detectors in near-Earth space have reported the occurrence of clusters of sub-micron dust particles that seemed unrelated to human spaceflight activities. In particular, data from the impact ionization detector onboard the HEOS-2 satellite indicate that such swarms of particles occur throughout the Earth's magnetosphere up to altitudes of 60 000 km-far beyond regions typically used by spacecraft. Further account of high-altitude clusters has since been given by the GEO-deployed GORID detector, however, explanations for the latter have so far only been sought in GEO spaceflight activity. This perspective piece reviews dust cluster detections in near-Earth space, emphasizing the natural swarm creation mechanism conjectured to explain the HEOS-2 data-i.e. the electrostatic disruption of meteoroids. Highlighting this mechanism offers a novel viewpoint on more recent near-Earth dust measurements. We further show that the impact clusters observed by both HEOS-2 and GORID are correlated with increased geomagnetic activity. This consistent correlation supports the notion that both sets of observations stem from the same underlying phenomenon and aligns with the hypothesis of the electrostatic breakup origin. We conclude that the nature of these peculiar swarms remains highly uncertain, advocating for their concerted investigation by forthcoming dust science endeavours, such as the JAXA/DLR DESTINY+ mission. This article is part of the theme issue 'Dust in the Solar System and beyond'.

Prospects for the observation of continuous gravitational waves from deformed fast-spinning white dwarfs

ABSTRACT There has been a growing interest within the astrophysics community in highly magnetized and fast-spinning white dwarfs (WDs), commonly referred to as HMWDs. WDs with these characteristics are quite uncommon and possess magnetic fields ≥106 G, along with short rotation periods ranging from seconds to just a few minutes. Based on our previous work, we analyse the emission of Gravitational Waves (GWs) in HMWDs through two mechanisms: matter accretion and magnetic deformation, which arise due to the asymmetry surrounding the star’s rotational axis. Here, we perform a thorough self-consistent analysis, accounting for rotation and employing a realistic equation of state to investigate the stability of stars. Our investigation focuses on the emission of gravitational radiation from six rapidly spinning WDs: five of them are situated within binary systems, while one is an AXP, proposed as a magnetic accreting WD. Furthermore, we apply the matter accretion mechanism alongside the magnetic deformation mechanism to assess the influence of one process on the other. Our discoveries indicate that these WDs could potentially act as GW sources for BBO and DECIGO, depending on specific parameters, such as their mass, the angle (α) between the magnetic and rotational axes, and the accumulated mass (δm) at their magnetic poles, which is influenced by the effect of matter accretion. However, detecting this particular class of stars using the LISA and TianQin space detectors seems unlikely due to the challenging combination of parameters such as a large δm, a large α angle and a small WD mass value.

In-orbit dark count rate performance and radiation damage high-temperature annealing of silicon avalanche photodiode single-photon detectors of the Micius satellite.

Silicon avalanche photodiode (APD) single-photon detectors in space are continuously affected by radiation, which gradually degrades their dark count performance. From August 2016 to June 2023, we conducted approximately seven years (2507 days) of in-orbit monitoring of the dark count performance of APD single-photon detectors on the Micius Quantum Science Experimental Satellite. The results showed that due to radiation effects, the dark count growth rate was approximately 6.79 cps/day @ -24 °C and 0.37 cps/day @ -55 °C, with a significant suppression effect on radiation-induced dark counts at lower operating temperature. Based on the proposed radiation damage induced dark count annealing model, simulations were conducted for the in-orbit dark counts of the detector, the simulation results are consistent with in-orbit test data. In May 2022, four of these detectors underwent a cumulative 5.7 hours high-temperature annealing test at 76 °C, dark count rate shows no measurable changes, consistent with annealing model. As of now, these ten APD single-photon detectors on the Micius Quantum Science Experimental Satellite have been in operation for approximately 2507 days and are still functioning properly, providing valuable experience for the future long-term space applications of silicon APD single-photon detectors.

Results and Perspectives of Timepix Detectors in Space—From Radiation Monitoring in Low Earth Orbit to Astroparticle Physics

In space application, hybrid pixel detectors of the Timepix family have been considered mainly for the measurement of radiation levels and dosimetry in low earth orbits. Using the example of the Space Application of Timepix Radiation Monitor (SATRAM), we demonstrate the unique capabilities of Timepix-based miniaturized radiation detectors for particle separation. We present the incident proton energy spectrum in the geographic location of SAA obtained by using Bayesian unfolding of the stopping power spectrum measured with a single-layer Timepix. We assess the measurement stability and the resiliency of the detector to the space environment, thereby demonstrating that even though degradation is observed, data quality has not been affected significantly over more than 10 years. Based on the SATRAM heritage and the capabilities of the latest-generation Timepix series chips, we discuss their applicability for use in a compact magnetic spectrometer for a deep space mission or in the Jupiter radiation belts, as well as their capability for use as single-layer X- and γ-ray polarimeters. The latter was supported by the measurement of the polarization of scattered radiation in a laboratory experiment, where a modulation of 80% was found.

Hypervelocity impact induced light flash experiments on single and dual layer Kapton targets to develop a time of flight space dust and debris detector

The impact flash from hypervelocity impact on thin (12.5 µm) Kapton film was observed. The projectile sizes ranged from 0.1 to 1 mm, with speeds from 2 to 5 km s−1 and penetrated the Kapton intact, leaving holes the same size as the projectile (to within measurement errors). The flash intensity (normalised to impactor mass) scaled with impact speed to the power 5.5. However, the data also suggest that at constant speed the intensity scales with the area of the hole in the Kapton and not the projectile mass (i.e. with some property of the target and not as a function of the projectile energy or momentum). Using two layers of Kapton, it was possible to construct a Time of Flight (TOF) system, which used the time of the onset of the flash in each layer to produce flight speeds accurate to within typically 1%. When compared to the projectile speed pre-impact, there was no indication of projectile deceleration during passage through the Kapton film. In addition, when PVDF acoustic sensors were placed on the Kapton film, they exhibited an electromagnetic “pick-up” signal from the impact of projectile on the Kapton, confirming suspicions of signal interference from past work with acoustic sensors. The ability of the light flash to provide accurate impact timing signals suggests the TOF system would be suitable for use as a cosmic dust or debris impact detector in space (e.g. Low Earth Orbit).

Direct Detection of Cosmic Rays with the Dark Matter Particle Explorer

The origin, acceleration, and propagation of high-energy cosmic rays is one of the most important questions in modern physics and astronomy. To fully uncover such a mystery, precise measurements of the energy spectra and anisotropies of cosmic rays, as well as multi-wavelength electromagnetic radiation from various types of energetic objects are required. The direct measurements of energy spectra of different species via particle detectors in space are an essential way to study cosmic ray physics. China launched the first space astronomical satellite, the Dark Matter Particle Explorer (DAMPE) in the end of 2015, which keeps operation in space for more than 7 years. The DAMPE has a relatively large acceptance and a high energy resolution, and has made important progresses in measuring the spectral structures of cosmic ray protons, helium nuclei, and boron-to-carbon and boron-to-oxygen ratios. These new measurements bring new insights in understanding the origin and propagation of cosmic rays. This paper reviews the instrumentation and operation of DAMPE, with an emphasis on its scientific results and physical implications in cosmic ray studies.

A Low‐Complexity Expectation Propagation Detector for OTFS

In this paper, we propose a low‐complexity expectation propagation (EP) detector for orthogonal time frequency space (OTFS) system with practical rectangular waveforms. In the high‐mobility scenario, OTFS is becoming a potential scheme for the sixth‐generation (6G) wireless communication system. However, the large size of the effective delay‐Doppler (DD) domain channel matrix brings unbearable computational complexity to the signal detection algorithm based on the matrix inversion. We propose a low‐complexity EP detector based on the sparsity and the block circulant structure of the effective channel covariance matrix in the DD domain. The proposed algorithm only requires log‐linear complexity. In addition, simulation results show that the proposed algorithm not only has the advantage of low complexity but also has good performance, which achieves a tradeoff between performance and complexity.

Analysis of Electric Sensor for Space Detectors: Mass Spectrometer, Particle Detector and CMOS/CCD Sensor

As a matter of fact, with the participation of government agencies and the exploration of private enterprises, space exploration is undergoing rapid development as well as change in recent years. With this in mind, these trends will continue to promote human exploration and utilization of space, providing more opportunities for scientific research, commercial applications and exploration. In order to realize accuracy observation, high precision detectors are necessary to be developed and implemented. To be specific, a large number of electric sensors are applied on the space detectors, including mass spectrometer, particle detector as well as CMOS/CCD image sensor, etc. On this basis, this paper presents the principles, structures and applications of these three electric sensors in detail. According to the analysis, this study also analyzes the existing shortcomings of the state-of-art facilities as well as proposes future developments. Overall, these results shed light on guiding further exploration of space detectors.

Study on the Performance of the GRANDProto300 Particle Detector Array by Simulation

The Giant Radio Array for Neutrino Detection (GRAND) is a proposed large-scale observatory designed to detect cosmic rays, gamma-rays, and neutrinos with energies exceeding 100 PeV. The GRANDProto300 experiment is proposed as the early stage of the GRAND project, consisting of a hybrid array of radio antennas and scintillator detectors. The latter, as a mature and traditional detector, is used to cross-check the nature of the candidate events selected from radio observations. In this study, we developed a simulation software called G4GRANDProto300, based on the Geant4 software package, to optimize the spacing of the scintillator detector array and to investigate its effective area. The analysis was conducted at various zenith angles under different detector spacings, including 300, 500, 600, 700, and 900 m. Our results indicate that, for large zenith angles used to search for cosmic-ray in the GRAND project, the optimized effective area is with a detector spacing of 500 m. The G4GRANDProto300 software that we developed could be used to further optimize the layout of the particle detector array in future work.

Analysis the Principle, Components and Functions of Electric Sensors for Space Detectors

Analysis the Principle, Components and Functions of Electric Sensors for Space Detectors

An introduction to the NIM A paper by V. Bindi et al. on the calibration and performance of the AMS-02 time of flight detector in space

An introduction to the NIM A paper by V. Bindi et al. on the calibration and performance of the AMS-02 time of flight detector in space

Exploring black hole-neutron star binary merger by detecting gravitational waves

Unlike black hole binary merger, the merger between a neutron star and a black hole will produce an abundant number of gravitational waves and electromagnetic waves. Using this information, scientists can easily find many properties of the universe and test the general relativity and some other gravitational theories. The detection of the gravitational wave from source is essential to develop the current knowledge of the gravitational force. From last century, scientists were trying to detect the gravitational waves, and as the time passes, the method of detection has already developed from on land detector to space detector in order to take more precise readings. This paper provides some basic information of the neutron star and the black hole, together with the formation of the binary neutron star-black hole system. The relationship between the neutron star and black hole is explained in this paper. The knowledge of the current methods of detecting gravitational waves is also provided and the paper specifically elaborated the space laser interferometry.