The South Pole-Aitken basin region,Moon: GIS-based geologic investigation using Kaguya elemental information

Using Geographic Information Systems (GIS), we performed comparative analysis among stratigraphic information and the Kaguya (SELENE) GRS data of the ∼2500-km-diameter South Pole-Aitken (SPA) basin and its surroundings. Results indicate that the surface rock materials (including ancient crater materials, mare basalts, and possible SPA impact melt) are average to slightly elevated in K and Th with respect to the rest of the Moon. Also, this study demonstrates that K and Th have not significantly changed since the formation of SPA. The elemental signatures of the impact basin of Fe, Ti, Si, O through time include evidence for resurfacing by ejecta materials and late-stage volcanism. The oldest surfaces of SPA are found to be oxygen-depleted during the heavy bombardment period relative to later stages of geologic development, followed by both an increase in silicon and oxygen, possibly due to ejecta sourced from outside of SPA, and subsequent modification due to mare basaltic volcanism, which increased iron and titanium within SPA. The influence of the distinct geologic history of SPA and surroundings on the mineralogic and elemental abundances is evident as shown in our investigation.     

国外紫外空间探测器发展综述

文章首先介绍了紫外线的谱段范围和特点,然后从紫外天文、对行星和卫星的空间探测和人造地球卫星等三个方面的应用,阐述了国外近年来紫外探测器发展和具体用途.最后针对紫外独有的特点,提出中国在该领域可能的发展方向和应重点研究的方向.     

The Mercury Atmospheric and Surface Composition Spectrometer for the MESSENGER Mission

The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) is one of seven science instruments onboard the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft en route to the planet Mercury. MASCS consists of a small Cassegrain telescope with 257-mm effective focal length and a 50-mm aperture that simultaneously feeds an UltraViolet and Visible Spectrometer (UVVS) and a Visible and InfraRed Spectrograph (VIRS). UVVS is a 125-mm focal length, scanning grating, Ebert-Fastie monochromator equipped with three photomultiplier tube detectors that cover far ultraviolet (115–180 nm), middle ultraviolet (160–320 nm), and visible (250–600 nm) wavelengths with an average 0.6-nm spectral resolution. It will measure altitude profiles of known species in order to determine the composition and structure of Mercury’s exosphere and its variability and will search for previously undetected exospheric species. VIRS is a 210-mm focal length, fixed concave grating spectrograph equipped with a beam splitter that simultaneously disperses the spectrum onto a 512-element silicon visible photodiode array (300–1050 nm) and a 256-element indium-gallium-arsenide infrared photodiode array 850–1,450 nm. It will obtain maps of surface reflectance spectra with a 5-nm resolution in the 300–1,450 nm wavelength range that will be used to investigate mineralogical composition on spatial scales of 5 km. UVVS will also observe the surface in the far and middle ultraviolet at a 10-km or smaller spatial scale. This paper summarizes the science rationale and measurement objectives for MASCS, discusses its detailed design and its calibration requirements, and briefly outlines observation strategies for its use during MESSENGER orbital operations around Mercury.     

大气成分探测红外光谱仪系统指标分析

由温室气体引起的全球气候变化和环境污染已经受到全世界的广泛关注。进行大气成分探测,对于更好地了解温室效应产生的细节、大气分子的光化学性质对臭氧层的影响以及大气污染机制都具有重要意义。由于大气成分种类较多,其红外吸收光谱密集且复杂,因此大气成分探测仪器需要有较高的光谱分辨能力和信噪比。文章进行了大气成分探测的总体指标需求分析,并据此确定了大气成分探测红外光谱仪的主要技术指标。为了满足指标要求,该光谱仪采用傅里叶变换红外光谱仪的总体方案。通过仪器性能影响因素分析和系统优化,使得该仪器的最终设计结果满足指标要求。     

The PRISMA payload optomechanical design, a high performance instrument for a new hyperspectral mission

PRISMA (PRecursore IperSpettrale della Missione Applicativa) hyperspectral instrument is an advanced hyperspectral sensor including a panchromatic camera at medium resolution. The instrument is the focus of the new Earth observation mission that a consortium of Italian companies has started developing under contract of Italian Space Agency. Key features of the instrument are the very high requirement for signal-to-noise and the high quality of data that have to be provided. To meet these demanding figures the optical system has been based on a high transmittance optical system, including a single mirror telescope and two prism spectrometers based on an innovative concept to minimize number of optical elements, while high performance detectors have been chosen for the photon detection. To provide the required data quality for the entire mission lifetime an accurate calibration unit (radiometric and spectral) will be included in the instrument optomechanical assembly. The thermo-mechanical design of the instrument is based on innovative concepts, considering that the use of prism spectrometers implies a tight control of temperature variations to guarantee the stability of all instrument features once in orbit. The presented paper describes the concepts and design principle of the optomechanical assembly of the instrument, at the present status of development.     

Development of an extreme ultraviolet imaging spectrometer for the BepiColombo mission

Extreme and far ultraviolet imaging spectrometers are proposed for the low-altitude orbiter of the BepiColombo mission. The UV instrument, consisting of the two spectrometers with common electronics, aims at measuring (1) emission lines from molecules, atoms and ions present in the Mercury’s tenuous atmosphere and (2) the reflectance spectrum of Mercury’s surface. The instrument pursues a complete coverage in UV spectroscopy. The extreme UV spectrometer covers the spectral range of 30–150 nm with the field of view of 5.0°, and the spectrum from 130 to 430 nm is obtained by the far UV spectrometer. The extreme UV spectrometer employs multi-layer coating technology to enhance its sensitivity at particular emission lines. This technology enables us to identify small ionospheric signatures such as He II (30.4 nm) and Na II (37.2 nm), which could not be detected with conventional optics.     

Alpha Particle X-Ray Spectrometer (APXS) on-board Chandrayaan-2 rover

Alpha Particle X-ray Spectrometer (APXS) payload configuration for Chandrayaan-2 rover has been completed recently and fabrication of mechanical assembly, PCB layout design and fabrication are in progress. Here we present the design and performance evaluation of various subsystems developed for APXS payload. The low energy threshold of <1 keV and the energy resolution of ∼150 eV at 5.9 keV, for the Silicon Drift Detector (SDD), as measured from the developed APXS electronics is comparable to the standard spectrometers available off-the-shelf. We have also carried out experiments for measuring fluorescent X-ray spectrum from various standard samples from the USGS catalog irradiated by the laboratory X-ray source ²⁴¹Am with 1 mCi activity. It is shown that intensities of various characteristic X-ray lines are well correlated with the respective elemental concentrations.     

基于遗传基因算法的中子能谱解谱程序研究

中子能谱解谱是制约中子能谱测量技术发展的瓶颈。遗传基因算法是人工智能领域一种全局收敛算法。通过探讨遗传基因算法在中子解谱领域的应用,基于遗传基因算法开发了中子能谱解谱程序,在多球谱仪中子能谱测量中取得了较好的结果。利用多球谱仪测量了²⁴¹Am-Be中子源和²⁵²Cf中子源中子能谱,与ISO8529推荐的标准谱进行了比较,验证了遗传基因算法解谱结果的可靠性。     

The Energetic Particle and Plasma Spectrometer Instrument on the MESSENGER Spacecraft

The Energetic Particle and Plasma Spectrometer (EPPS) package on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission to Mercury is composed of two sensors, the Energetic Particle Spectrometer (EPS) and the Fast Imaging Plasma Spectrometer (FIPS). EPS measures the energy, angular, and compositional distributions of the high-energy components of the in situ electrons (>20 keV) and ions (>5 keV/nucleon), while FIPS measures the energy, angular, and compositional distributions of the low-energy components of the ion distributions (<50 eV/charge to 20 keV/charge). Both EPS and FIPS have very small footprints, and their combined mass (∼3 kg) is significantly lower than that of comparable instruments.     

微振动对星载傅里叶变换光谱仪的影响分析

文章介绍了一种利用星载傅里叶光谱仪(FTS)进行大气成份探测方法。该光谱仪基于动镜干涉原理,采用空心角镜摆臂扫描、计量激光进行触发的采样方式,实现光谱探测。这种设计尽可能的减轻了FTS在采样过程中卫星平台的振动对干涉效果和光谱数据的影响。文章首先介绍了星载傅里叶变换光谱仪的在轨工作模式、系统组成和干涉模块的光学方案,给出了微振动对傅里叶光谱仪干涉信号和光谱信号影响的数学模型,针对卫星平台微振动的频率和振幅特性,开展了典型工况条件下干涉信号和光谱信号的仿真计算。仿真结果显示随着振动量级增大,光谱图上的鬼线幅值明显增大;另外,延迟匹配精度对探测精度具有重要影响,延迟匹配误差越大,产生的鬼线幅值越大。分析表明,在小于卫星平台的微振动幅度(30×10-3gn)时,微振动对星载傅里叶变换光谱仪的影响可以控制在可接受范围内。