Current and near-term advances in Earth observation for ecological applications

There is an unprecedented array of new satellite technologies with capabilities for advancing our understanding of ecological processes and the changing composition of the Earth’s biosphere at scales from local plots to the whole planet.We identified 48 instruments and 13 platforms with multiple instruments that are of broad interest to the environmental sciences that either collected data in the 2000s,were recently launched,or are planned for launch in this decade.We have restricted our review to instruments that primarily observe terrestrial landscapes or coastal margins and are available under free and open data policies.We focused on imagers that passively measure wavelengths in the reflected solar and emitted thermal spectrum.The suite of instruments we describe measure land surface characteristics,including land cover,but provide a more detailed monitoring of ecosystems,plant communities,and even some species then possible from historic sensors.The newer instruments have potential to greatly improve our understanding of ecosystem functional relationships among plant traits like leaf mass area(LMA),total nitrogen content,and leaf area index(LAI).They provide new information on physiological processes related to photosynthesis,transpiration and respiration,and stress detection,including capabilities to measure key plant and soil biophysical properties.These include canopy and soil temperature and emissivity,chlorophyll fluorescence,and biogeochemical contents like photosynthetic pigments(e.g.,chlorophylls,carotenoids,and phycobiliproteins from cyanobacteria),water,cellulose,lignin,and nitrogen in foliar proteins.These data will enable us to quantify and characterize various soil properties such as iron content,several types of soil clays,organic matter,and other components.Most of these satellites are in low Earth orbit(LEO),but we include a few in geostationary orbit(GEO)because of their potential to measure plant physiological traits over diurnal periods,improving estimates of water and carbon budgets.We also include a few spaceborne active LiDAR and radar imagers designed for quantifying surface topography,changes in surface structure,and 3-dimensional canopy properties such as height,area,vertical profiles,and gap structure.We provide a description of each instrument and tables to summarize their characteristics.Lastly,we suggest instrument synergies that are likely to yield improved results when data are combined.

国外星载对地探测激光雷达发展分析

近年来,世界各航天强国加速推进星载激光雷达研制,多颗搭载对地探测激光雷达的专星发射升空,有望大幅提升卫星对地探测能力。本文主要针对近年来国外取得显著进展的星载激光测高雷达、星载大气激光雷达以及星载多普勒激光测风雷达三种典型星载对地探测激光雷达技术,介绍其当前发展现状,并总结其未来发展趋势。

机载高光谱激光雷达成像技术发展与应用

高光谱激光雷达作为一种新型的主动式对地观测技术手段,结合了传统激光雷达三维空间信息获取和被动高光谱成像技术的优势,可实现高空间分辨和高光谱分辨的一体化成像探测,已成为未来遥感技术发展的重要方向。首先,从激光雷达空谱一体化数据获取技术研究进展出发,论述了高光谱激光雷达成像技术的发展历程并分析了其独特的优势。随后,结合机载平台应用发展,针对机载高光谱激光雷达系统研制中的关键技术难点,对激光发射单元、接收探测单元和数据处理单元的发展进行了阐述。最后,面向该新型遥感技术的未来发展前景,重点分析了机载高光谱激光雷达在地物覆盖分类、植被遥感监测、海洋资源探测和军事目标侦查等领域中的重大应用潜力,并针对其未来推广应用进行了展望与分析。机载高光谱激光雷达凭借其空谱一体化数据获取优势,将来有望发展成为一种新型遥感技术门类。

偏振激光雷达对地观测遥感

激光雷达遥感可获取地物的三维结构信息,偏振遥感可实现"强光弱化与弱光强化"的信息增强,两者主被动光学遥感组合为下一代对地观测多维光学遥感新模式的研发提供一条可行的途径。事实上偏振激光雷达这一概念提出较早,但其已开展的应用主要集中在大气监测领域,研究重点侧重于激光后向散射去极化技术等方面,进一步发展到探测大气气溶胶含量及针对相关任务的信息增强技术研发等;但在其他领域,偏振激光雷达的遥感应用极其有限,而理论上偏振激光雷达具有推广到复杂地物遥感的可能性。从其两种组成模式的遥感原理角度出发探讨偏振激光雷达对地观测遥感可能实现的机理基础,并分析了其技术发展的趋势,为后续相关遥感技术的研发及其在农业、环境、海洋、空间探测等不同领域中的应用指出了可能的切入点。

多光谱对地观测激光雷达接收通道选择方法

多光谱对地观测激光雷达是一种新型植被监测手段,其应用越来越广泛。现有多光谱对地观测激光雷达系统大多采用光栅分光、多通道光敏阵列探测的数据接收模式。单纯地增加接收通道以提高光谱分辨率、增加接收光谱范围会带来数据冗余、系统集成难度大以及成本过高等问题。讨论了如何确定通道数目并通过闪耀光栅以及中心闪耀波长的选取将特征波长调节至合适通道的中心位置;同时,利用基于主成分分析的特征权重波长修正方法,对落在通道外或不在通道中心位置的特征波长进行修正。在不减少植被光谱信息的前提下,此过程可提高信息接收的有效性,还在一定程度上对波长选择理论进行了补充,提高了多光谱对地观测激光雷达系统在实际应用中的适应性。