Low-cost volcano surveillance from space: case studies from Etna, Krafla, Cerro Negro, Fogo, Lascar and Erebus

 Satellite data offer a means of supplementing ground-based monitoring during volcanic eruptions, especially at times or locations where ground-based monitoring is difficult. Being directly and freely available several times a day, data from the advanced very high resolution radiometer (AVHRR) offers great potential for near real-time monitoring of all volcanoes across large (3000×3000 km) areas. Herein we describe techniques to detect and locate activity; estimate lava area, thermal flux, effusion rates and cumulative volume; and distinguish types of activity. Application is demonstrated using data for active lavas at Krafla, Etna, Fogo, Cerro Negro and Erebus; a pyroclastic flow at Lascar; and open vent systems at Etna and Stromboli. Automated near real-time analysis of AVHRR data could be achieved at existing, or cheap to install, receiving stations, offering a supplement to conventional monitoring methods. Received: 21 January 1997 / Accepted: 3 April 1997     

南极冰貌卫星影像条带噪声的剔除

本文在简要叙述条带噪声形成原因的基础上 ,针对南极地区的ASTER 1A的可见光影像中出现的条带噪声的现象 ,通过设计了基于切比雪夫窗、凯瑟窗的FIR滤波器和约束最小二乘FIR滤波器对其条带噪声进行剔除 ,这两种滤波器能够尽可能地剔除条带 ,同时使影像的灰度分布发生最小畸变。并通过与其他方法 (例如 :低通滤波 ,直方图匹配等 )比较 ,说明这两种滤波的方法优于其他的方法     

硬X射线成像仪量能器测试系统的设计与实现

硬X射线成像仪(Hard X-ray Imager, HXI)是先进天基太阳天文台(Advanced Space-based Solar Observatory, ASO-S)的3大载荷之一, 其中量能器作为其重要组成部分, 承担着观测30--200keV能段的太阳硬X射线的任务. 在卫星发射之前, 需要开展大量的测试工作, 以确保HXI量能器的各项功能和性能满足设计需求. HXI量能器通道数众多, 内含99个溴化镧探测器, 分别由8块相同的前端电子学板控制. 除了对各个通道的性能进行测试外, 地检系统还需模拟量能器在轨面对不同太阳活动时的运行情况, 对量能器进行全面完备的测试. 此外, 地检系统还需足够稳定, 能满足量能器在单机测试、环境试验、热真空与振动等多个不同测试项目的长时间测试需求. 为此, 设计了地检板与上位机软件, 结合放射源、直流电源、高压模块等组成一套HXI量能器的地检系统, 对8块前端电子学板实现同步配置与管理, 能高效完成指令发送与数据接收, 满足量能器最大数据输出带宽400Mbps的需求. 利用该系统, 在地面完成了HXI量能器的功能、性能验证, 获得了量能器的线性、死时间、能量分辨率等各项性能指标, 为HXI量能器的在轨高性能运行提供了保障.     

ASO-S卫星工程科学应用系统的数据库设计

先进天基太阳天文台(Advanced Space-based Solar Observatory, ASO-S)卫星是我国首颗太阳观测卫星, 主要观测太阳耀斑和日冕物质抛射以及产生它们的磁场结构. ASO-S卫星的科学应用系统是科学卫星工程的6大系统之一, 它连接科学用户和卫星数据, 为将卫星的科学数据转化为科学成果提供保障. 科学应用系统的数据库是连接软件与海量数据的枢纽, 为科学数据生产和用户服务及运行提供数据层的支撑. 介绍了科学应用系统的数据库架构设计、数据库的选择以及数据库性能优化和表样例. 这里的数据库包括观测计划、工程参数、运维日志、科学数据、定标数据和特征事件识别等数据库. 这些数据库的建设将为ASO-S卫星工程科学应用系统的顺利运行提供数据支撑, 也可以为未来其他科学卫星类似数据库的搭建提供参考和借鉴.     

Geography Deserts: State and Regional Variation in the Formal Opportunity to Learn Geography in the United States, 2005–2015

The formal opportunity to learn geography in the United States is unevenly distributed across space, creating possible geography deserts. Data on the number of exams taken in Advanced Placement Human Geography (APHG) and bachelor’s degrees earned in geography are mapped at the state and regional scales. Normalized rates are ranked and grouped into quintiles. For APHG exams, states in the southeastern region of the United States are in the uppermost quintiles while states in the northeastern region are in the lowermost quintiles. The pattern for bachelor’s degrees in geography is somewhat the spatial inverse of that for APHG.     

Degradation Pathway of the Photochemical Oxidation of Ethylenediaminetetraacetate (EDTA) in the UV/H2O2-process

The degradation pathway for the oxidation of EDTA in the UV/H₂O₂-process was investigated. In absence of iron ions, the mineralization of EDTA is dominated by the reaction of the HO-radicals generated by the photolysis of H₂O₂. The organic degradation products iminodiacetate (IMDA), glycinate, oxamate, glyoxylate, oxalate and formate, and the inorganic degradation products carbon dioxide, ammonia, nitrate, nitrite, and cyanate were found. In the presence of iron ions, photolytic decarboxylation processes inside the complex get an important role during degradation, and the organic degradation products ethylenediaminetriacetate (ED3A), ethylenediaminediacetate (EDDA), ethylenediaminemonoacetate (EDMA) were also found. By combining product studies with balances of carbon and nitrogen, the degradation pathway in the UV/H₂O₂-process could be elucidated. The degradation of EDTA was fast (k_deg = 0.012 s^–1), and no toxic degradation products were identified. Therefore, the process is well suited for the elimination of EDTA in water treatment.     

Assimilation of ASAR data with a hydrologic and semi-empirical backscattering coupled model to estimate soil moisture

The most promising approach for studying soil moisture is the assimilation of observation data and computational modeling.However,there is much uncertainty in the assimilation process,which affects the assimilation results.This research developed a one-dimensional soil moisture assimilation scheme based on the Ensemble Kalman Filter(EnKF)and Genetic Algorithm(GA).A two-dimensional hydrologic model-Distributed Hydrology-Soil-Vegetation Model(DHSVM)was coupled with a semi-empirical backscattering model(Oh).The Advanced Synthetic Apertture Radar(ASAR)data were assimilated with this coupled model and the field observation data were used to validate this scheme in the soil moisture assimilation experiment.In order to improve the assimilation results,a cost function was set up based on the distance between the simulated backscattering coefficient from the coupled model and the observed backscattering coefficient from ASAR.The EnKF and GA were used to re-initialize and re-parameterize the simulation process,respectively.The assimilation results were compared with the free-run simulations from hydrologic model and the field observation data.The results obtained indicate that this assimilation scheme is practical and it can improve the accuracy of soil moisture estimation significantly.