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- 实验方案
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Thermal structure of a hot non-flaring corona from Hinode/EIS
摘要： Aims. In previous studies, a very hot plasma component has been diagnosed in solar active regions through the images in three different narrow-band channels of Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). This diagnostic from extreme ultraviolet (EUV) imaging data has also been supported by the matching morphology of emission in the hot Ca XVII line, as observed with Extreme-Ultraviolet Imaging Spectrometer (EIS) on board Hinode. This evidence is debated because of the unknown distribution of the emission measure along the line of sight. Here we investigate in detail the thermal distribution of one such region using EUV spectroscopic data. Methods. In an active region observed with SDO/AIA, Hinode/EIS, and X-ray telescope (XRT), we select a sub-region with a very hot plasma component and another cooler sub-region for comparison. The average spectrum is extracted for both, and 14 intense lines are selected for analysis that probe the 5.5 < log T < 7 temperature range uniformly. From these lines, the emission measure distributions are reconstructed with the Markov-chain Monte Carlo method. Results are cross-checked in comparison with the two sub-regions, with a different inversion method, with the morphology of the images, and with the addition of fluxes measured with narrow, and broadband imagers. Results. We find that, whereas the cool region has a flat and featureless distribution that drops at temperature log T ≥ 6.3, the distribution of the hot region shows a well-defined peak at log T = 6.6 and gradually decreasing trends on both sides, thus supporting the very hot nature of the hot component diagnosed with imagers. The other cross-checks are consistent with this result. Conclusions. This study provides a completion of the analysis of active region components, and the resulting scenario supports the presence of a minor very hot plasma component in the core, with temperatures log T > 6.6.
关键词： techniques: imaging spectroscopy,Sun: UV radiation,Sun: corona,techniques: spectroscopic,Sun: X-rays, gamma rays
更新于2025-09-23 15:23:52
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Spatial and Temporal Stability of Airglow Measured in the Meinel Band Window at 1191.3 nm
摘要： We report on the temporal and spatial fluctuations in the atmospheric brightness in the narrow band between Meinel emission lines at 1191.3 nm using a λ/Δλ = 320 near-infrared instrument. We present the instrument design and implementation, followed by a detailed analysis of data taken over the course of a night from Table Mountain Observatory. At low airmasses, the absolute sky brightness at this wavelength is found to be 5330 ± 30 nW m?2 sr?1, consistent with previous measurements of the inter-band airglow at these wavelengths. This amplitude is larger than simple models of the continuum component of the airglow emission at these wavelengths, confirming that an extra emissive or scattering component is required to explain the observations. We perform a detailed investigation of the noise properties of the data and find no evidence for a noise component associated with temporal instability in the inter-line continuum. This result demonstrates that in several hours of ～100 s integrations the noise performance of the instrument does not appear to significantly degrade from expectations, giving a proof of concept that near-infrared line intensity mapping may be feasible from ground-based sites.
关键词： techniques: imaging spectroscopy,site testing,atmospheric effects
更新于2025-09-23 15:23:52
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Achievable noise performance of spectroscopic prototype DEPFET detectors
摘要： A new generation of spectroscopic X-ray DEPFET detectors has been produced in the course of the detector development for the Wide Field Imager (WFI) of Athena. These devices served to perform a detailed analysis of the noise composition, which was enabled by the development of appropriate test algorithms. A result of the analysis is the distinction of different components, which sum up to the total noise. In particular the contribution of shot noise, white noise and 1/f noise to the readout noise is determined as well as the signal noise caused by the generation of charge carriers. The resulting parametrization enables the adaptation and optimization of operation modes to given purposes. The studied prototype detectors included 64×64 pixels with a linear gate design and provided an excellent noise, below 1.6 e?ENC at a readout time faster than 10 μs/pixel and a temperature of -80 ?C in rolling-shutter operation. This performance is enabled by an extended signal integration time. A further noise reduction is prevented by the signal noise, caused by charge carrier generation. In order to demonstrate the low noise properties of the DEPFET transistor, the measurement conditions were adapted and a noise of 0.95 e?ENC was measured at the expense of the sensor size — by operating only parts of the sensor in window mode — and dynamic range — by using the Al Kα line at about 1.49 keV for calibration.
关键词： Imaging spectroscopy,Solid state detectors,Instrumental noise,X-ray detectors and telescopes
更新于2025-09-23 15:23:52
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Spectroscopic DEPFETs at high frame rates using window mode
摘要： An active pixel sensor like an array of DEPFET (DEpleted P-channel Field Effect Transistor) pixels allows for very flexible operation modes and an adaptability of the sensor design to the specific needs of the scientific instrument objectives. For a very high time resolution at the order of one microsecond, a full parallel readout of all pixels is required. Every readout node needs to be connected to readout electronics separately. Furthermore, to preserve a good spectroscopic performance, the integration of a storage functionality into each pixel prevents the influence of events occurring during the readout process and provoking an incorrect energy information. The energy of such events is detected incorrectly and is not falsifiable with a subsequent analysis. An active pixel sensor based on a DEPFET with internal storage and wired for full parallel readout is in production and will be available for testing in the future. Alternatively, the ability of an active pixel sensor to be read out in window (region-of-interest readout) mode allows for the investigation of the behavior at high frame rates at the order of 100 kHz for DEPFET devices with and without storage functionality.
关键词： Imaging spectroscopy,Solid state detectors,X-ray detectors and telescopes
更新于2025-09-23 15:23:52
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Mapping salt marsh soil properties using imaging spectroscopy
摘要： Tidal salt marshes sequester and store blue carbon at both short and long time scales. Marsh soils shape and maintain the ecosystem by supporting complex biogeochemical reactions, deposition of sediment, and accumulation of organic matter. In this study, we examined the potential of imaging spectroscopy techniques to indirectly quantify and map tidal marsh soil properties at a National Estuarine Research Reserve in Georgia, USA. A framework was developed to combine modern digital image processing techniques for marsh soil mapping, including object-based image analysis (OBIA), machine learning modeling, and ensemble analysis. We also evaluated the efficacy of airborne hyperspectral sensors in estimating marsh soil properties compared to spaceborne multispectral sensors, WorldView-2 and QuickBird. The pros and cons of object-based modeling and mapping were assessed and compared with traditional pixel-based mapping methods. The results showed that the designed framework was effective in quantifying and mapping three marsh soil properties using the composite reflectance from salt marsh environment: soil salinity, soil water content, and soil organic matter content. Multispectral sensors were successful in quantifying soil salinity and soil water content but failed to model soil organic matter. The study also demonstrated the value of minimum noise fraction transformation and ensemble analysis techniques for marsh soil mapping. The results suggest that imaging spectroscopy based modeling is a promising tool to quantify and map marsh soil properties at a local scale, and is a potential alternative to traditional soil data acquisition to support carbon cycle research and the conservation and restoration of tidal marshes.
关键词： Salt marsh,Object-based modeling,Soil properties,Imaging spectroscopy,Machine learning
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Global VSWIR Imaging Spectroscopy and the 2017 Decadal Survey
摘要： On the 5th of January 2018, an unedited prepublication version of the 2017 Decadal Survey was released titled, “Thriving on Our Changing Planet A Decadal Strategy for Earth Observation from Space.” This 700 page document that was developed over more than two years with broad input from the Earth science and applications communities. Five targeted observables are indicated as observing system priorities in this early release version. One of these is surface biology and geology. In this category, a set of science and applications targets are identified including: ground/water temperature, snow reflectivity, active geologic processes, vegetation traits and algal biomass. The candidate measurement approach is described as, “Hyperspectral imagery in the visible and shortwave infrared, multi- or hyperspectral imagery in the thermal IR.” This paper reviews some of the key new science and applications objectives, and outlines some measurement approaches that could be used to address this guidance in the area of global visible to short wavelength infrared imaging spectroscopy.
关键词： Earth system,Decadal Survey,VSWIR,Imaging Spectroscopy
更新于2025-09-23 15:21:21
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First survey of Wolf-Rayet star populations over the full extension of nearby galaxies observed with CALIFA
摘要： The search of extragalactic regions with conspicuous presence of Wolf-Rayet (WR) stars outside the Local Group is challenging task owing to the di?culty in detecting their faint spectral features. In this exploratory work, we develop a methodology to perform an automated search of WR signatures through a pixel-by-pixel analysis of integral ?eld spectroscopy (IFS) data belonging to the Calar Alto Legacy Integral Field Area survey, CALIFA. This procedure has been applied to a sample of nearby galaxies spanning a wide range of physical, morphological, and environmental properties. This technique allowed us to build the ?rst catalogue of regions rich in WR stars with spatially resolved information, and enabled us to study the properties of these complexes in a two-dimensional (2D) context. The detection technique is based on the identi?cation of the blue WR bump (around He ii λ4686 ?, mainly associated with nitrogen-rich WR stars; WN) and the red WR bump (around C iv λ5808 ?, mainly associated with carbon-rich WR stars; WC) using a pixel-by-pixel analysis that maximizes the number of independent regions within a given galaxy. We identi?ed 44 WR-rich regions with blue bumps distributed in 25 out of a total of 558 galaxies. The red WR bump was identi?ed only in 5 of those regions. Most of the WR regions are located within one e?ective radius from the galaxy centre, and around one-third are located within ～1 kpc or less from the centre. We found that the majority of the galaxies hosting WR populations in our sample are involved in some kind of interaction process. Half of the host galaxies share some properties with gamma-ray burst (GRB) hosts where WR stars, such as potential candidates to the progenitors of GRBs, are found. We also compared the WR properties derived from the CALIFA data with stellar population synthesis models, and con?rm that simple star models are generally not able to reproduce the observations. We conclude that other e?ects, such as binary star channel (which could extend the WR phase up to 10 Myr), fast rotation, or other physical processes that cause the loss of observed Lyman continuum photons, very likely a?ect the derived WR properties, and hence should be considered when modelling the evolution of massive stars.
关键词： techniques: imaging spectroscopy,galaxies: ISM,galaxies: starburst,stars: Wolf-Rayet
更新于2025-09-23 15:21:21
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Coupled retrieval of the three phases of water from spaceborne imaging spectroscopy measurements
摘要： Measurements of reflected solar radiation by imaging spectrometers can quantify water in different states (solid, liquid, gas) thanks to the discriminative absorption shapes. We developed a retrieval method to quantify the amount of water in each of the three states from spaceborne imaging spectroscopy data, such as those from the German EnMAP mission. The retrieval couples atmospheric radiative transfer simulations from the MODTRAN5 radiative transfer code to a surface reflectance model based on the Beer-Lambert law. The model is inverted on a per-pixel basis using a maximum likelihood estimation formalism. Based on a unique coupling of the canopy reflectance model HySimCaR and the EnMAP end-to-end simulation tool EeteS, we performed a sensitivity analysis by comparing the retrieved values with the simulation input leading to an R2 of 0.991 for water vapor and 0.965 for liquid water. Furthermore, we applied the algorithm to airborne AVIRIS-C data to demonstrate the ability to map snow/ice extent as well as to a CHRIS-PROBA dataset for which concurrent field measurements of canopy water content were available. The comparison between the retrievals and the ground measurements showed an overall R2 of 0.80 for multiple crop types and a remarkable clustering in the regression analysis indicating a dependency of the retrieved water content from the physical structure of the vegetation. In addition, the algorithm is able to produce smoother and more physically-plausible water vapor maps than the ones from the band ratio approaches used for multispectral data, since biases due to background reflectance are reduced. The demonstrated potential of imaging spectroscopy to provide accurate quantitative measures of water from space will be further exploited using upcoming spaceborne imaging spectroscopy missions like PRISMA or EnMAP.
关键词： Atmospheric correction,EnMAP,Canopy water content,Water vapor,Imaging spectroscopy
更新于2025-09-23 15:21:01
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The long-wave infrared (8-12 μm) spectral features of selected rare earth element—Bearing carbonate, phosphate and silicate minerals
摘要： Rare earth elements (REEs) are a group of metals essential to high technology industries. This high demand, combined with a high supply risk, has led to an understanding that REEs are critical to society. Despite the potential that hyperspectral imaging (HSI) data offers for a fast and non-invasive characterization of the REEs, it is still poorly understood whether REEs have some information in the long-wave infrared (LWIR; 8–12 μm) wavelength range that can be used for their identification. To partially fill this gap, we have investigated the spectroscopy of twelve REE-bearing mineral samples using relatively high spatial and spectral resolution LWIR hyperspectral imaging data. These samples were formerly characterized using electron probe microanalysis (EPMA), scanning electron microscopy (SEM), and hyperspectral imaging data acquired in the 0.4–2.5 μm wavelength range. Results from these analyses were compared to and used to guide the analysis of the HSI data recorded in the LWIR range. This information was further compared to a reference spectral library of rare earth oxides. Our findings suggest that the spectral features of the samples can generally be traced to the asymmetric degenerate stretching and bending modes of the X-O (X = C, Si, P) groups. Moreover and contrary to what has been observed in the shorter wavelengths, there are no definitive spectral features in the LWIR wavelength region that could be assigned to any specific REE.
关键词： Imaging spectroscopy,Long-wave infrared,Rare earth element,Hyperspectral,Mineral
更新于2025-09-23 15:21:01
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LAMOST CCD camera-control system based on RTS2
摘要： The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is the largest existing spectroscopic survey telescope, having 32 scientific charge-coupled-device (CCD) cameras for acquiring spectra. Stability and automation of the camera-control software are essential, but cannot be provided by the existing system. The Remote Telescope System 2nd Version (RTS2) is an open-source and automatic observatory-control system. However, all previous RTS2 applications were developed for small telescopes. This paper focuses on implementation of an RTS2-based camera-control system for the 32 CCDs of LAMOST. A virtual camera module inherited from the RTS2 camera module is built as a device component working on the RTS2 framework. To improve the controllability and robustness, a virtualized layer is designed using the master-slave software paradigm, and the virtual camera module is mapped to the 32 real cameras of LAMOST. The new system is deployed in the actual environment and experimentally tested. Finally, multiple observations are conducted using this new RTS2-framework-based control system. The new camera-control system is found to satisfy the requirements for automatic camera control in LAMOST. This is the first time that RTS2 has been applied to a large telescope, and provides a referential solution for full RTS2 introduction to the LAMOST observatory control system.
关键词： telescopes,methods: observational,techniques: imaging spectroscopy,instrumentation: detectors
更新于2025-09-19 17:15:36