The impact on tsunami detection from space using GNSS-reflectometry when combining GPS with GLONASS and Galileo

The devastating Sumatra tsunami in 2004 demonstrated the need for a tsunami early warning system in the Indian Ocean. Such a system has been installed within the German-Indonesian Tsunami Early Warning System (GITEWS) project. Tsunamis are a global phenomenon and for global observations satellites are predestined. Within the GITEWS project a feasibility study on a future tsunami detection system from space has therefore been carried out. The Global Navigation Satellite System Reflectometry (GNSS-R) is an innovative way of using GNSS signals for remote sensing. It uses ocean reflected GNSS signals for sea surface altimetry. With a dedicated Low Earth Orbit (LEO) constellation of satellites equipped with GNSS-R receivers, densely spaced sea surface height measurements could be established to detect tsunamis. Some general considerations on the geometry between LEO and GNSS are made in this simulation study. It exemplary analyzes the detection performance of a GNSS-R constellation at 900 km altitude and 60° inclination angle when applied to the Sumatra tsunami as it occurred in 2004. GPS is assumed as signal source and the combination with GLONASS and Galileo signals is investigated. It can be demonstrated, that the combination of GPS and Galileo is advantageous for constellations with few satellites while the combination with GLONASS is preferable for constellations with many satellites. If all three GNSS are combined, the best detection performance can be expected for all scenarios considered. In this case an 18 satellite constellation will detect the Sumatra tsunami within 17 min with certainty, while it takes 53 min if only GPS is considered.     

Responses to satellite remote sensing opportunities in East and Southern Africa

Since 1978 the U.S. Agency for International Development (USAID) has funded a regional remote sensing project for East and Southern Africa. The project, hosted by the Regional Centre for Services in Surveying Mapping and Remote Sensing, has provided a programme of training courses, user services and project support. This included the equipping and establishment of a photo-laboratory complex for processing Landsat images and the provision of advice and support for agencies undertaking natural resources analysis.Response to the training programme has been very good. Courses are usually over subscribed and there is a continued demand for training. Assessments of the courses by participants are highly positive and the courses have featured consultants of international calibre. Requests for follow-up courses, and for specialist group training indicate a strong response to this training activity. User services are active, consultations with staff, use of the browse file and interpretation equipment and the purchase of data for project work all produce an average demand of 12 active enquiries per working week. The photo-laboratory is particularly active and demand for products exceeds available capacity.Project work is now being supported but limited resources restrict the range and amount of project activity. Response to the opportunities offered for projects has been favourable and this activity is ripe for expansion. The difficulty in expanding to meet the expressed demand is primarily financial. The east and southern Africa region is not economically strong and has a great need for natural resources data for development work and planning. The responses to satellite remote sensing opportunities will be limited by these financial constraints which effectively means by the level of international aid directed to this activity. For such aid to be effective it must be coordinated and firmly attached to the region. Such coordinated aid programmes would avoid fragmentation of distribution and applications work. Fragmentation could seriously disrupt the present growth in natural resources activity based on remote sensing data from satellites. The lack of financing for a regional ground receiving station is also a significant limiting factor.     

GNSS遥感探测卫星星座设计

随着全球导航卫星系统（Global Navigation Satellite System,GNSS）掩星大气探测技术的兴起,GNSS遥感探测数据在气象数据资源中逐步占据重要地位,但是目前的掩星探测数量远不能满足数值天气预报等应用的需求,未来更需要充分利用GNSS信号资源,开展更大规模的GNSS掩星卫星星座探测.本文以世界气象组织发布的大气海洋数据需求为参考,提出新一代GNSS遥感探测星座任务需求与设计约束.在理想大气模型假设下,利用几何解析方法研究了探测卫星星座构型参数对探测性能的影响,并建立了新一代GNSS遥感探测卫星星座设计基本准则.以风云卫星为子星座,给出了星座规模同为40颗的三种GNSS遥感探测微纳卫星星座设计方案.研究结果表明,具备该规模的探测星座可满足数值天气预报等气象应用的最低数据需求,三种构型方案中,由高、中、低倾角三组Walker子星座与风云卫星子星座组建的GNSS遥感探测星座探测性能最优.      

Training opportunities in remote sensing in India

The paper deals with the Indian experience in training the resources scientists in the fast developing field of remote sensing and the facilities available for obtaining such training in India. The necessity of imparting training to the scientists at different levels is brought out. An outline of the training curriculum of a leading institution is described in some detail.     

The use of remote sensing in global biosystem studies

Remote sensing techniques, if properly employed, offer definite advantages to studies of the Earth's environment and resources on a global scale. A remote sensing strategy is presented for selective sampling of the properties and changes in the atmosphere, the oceans and on land in support of global biosystems research as proposed by NASA, including mineral cycling, ocean and terrestrial productivity, perturbation effects and biospheric responses. It is shown that remote sensors on satellites and aircraft should be used to update existing data bases and to monitor areas of high productivity or rapid change, rather than attempting to produce a costly inventory of all biosphere resources and processes.     

Comprehensive comparison of VHR 3D spatial data acquired from IKONOS and TerraSAR-X imagery

With the launch of very high resolution (VHR) optical and synthetic aperture radar (SAR) remote sensing satellites such as IKONOS and TerraSAR-X, a new era has begun in 3D spatial data acquirement. IKONOS provided the first VHR data is still being preferred for many remote sensing applications. TerraSAR-X is considered as a revolution in SAR imaging as a result of 1 m resolution imaging capability. The imaging principles of these satellites are quite different and include advantages and disadvantages that have considerable effects on the quality of acquired 3D spatial data.     

遥感卫星数据传输技术发展分析

在分析遥感卫星对该技术总体需求的基础上,从数据率、频段选择、数据压缩、调制解调、数据安全、编译码等几个方面对此项技术的发展进行了分析和预测,并提出了相应的对策。     

基于认知无线电的GEO与LEO卫星频谱共存

随着新的宽带多媒体业务的发展，宽带无线频谱的需求日益增长。同时，低轨道（LEO）卫星由于其传输损耗低、传播时延小而被大规模部署。为了更好地利用频谱资源，卫星通信系统普遍采用高轨道（GEO）卫星与LEO卫星频谱共存的方案来提高频谱利用率。在频谱共存的过程中，提出了一种基于动态阈值的能量检测与波束跳跃相结合的算法，以减小LEO对GEO卫星的干扰。首先对LEO卫星的信噪比进行估计并实时选择最优阈值，然后利用基于动态阈值的能量检测算法对GEO卫星信号进行判别，最后根据判断的结果进行波束调整。仿真结果表明，提出的基于动态阈值的能量检测算法的检测误差明显低于传统的基于固定阈值的能量检测算法和基于二阶循环统计量的频谱感知方法。当信噪比低于-10dB的情况下，检测误差低于0.2；而当信噪比高于-5dB时，检测误差趋近于0。     

中国卫星的发展及应用

总结了我国卫星的发展道路。指出20年来我国卫星的发展主攻方向是应用卫星,主要目标是高中低三类轨道的通信、遥感和科学实验卫星,发展的步骤采取了步数少、步距大、起点高的途径,发展方针是依靠自力更生和全国大协作。文章扼要介绍了自80年代我国卫星转入应用后的情况,已在教育、广播、通信、资源、测绘、气象、科学研究和国防建设等领域应用并作出了巨大贡献。文章最后指出了我国90年代卫星应用的光明前景。     

GNSS reflectometry and remote sensing: New objectives and results

The Global Navigation Satellite System (GNSS) has been a very powerful and important contributor to all scientific questions related to precise positioning on Earth’s surface, particularly as a mature technique in geodesy and geosciences. With the development of GNSS as a satellite microwave (L-band) technique, more and wider applications and new potentials are explored and utilized. The versatile and available GNSS signals can image the Earth’s surface environments as a new, highly precise, continuous, all-weather and near-real-time remote sensing tool. The refracted signals from GNSS radio occultation satellites together with ground GNSS observations can provide the high-resolution tropospheric water vapor, temperature and pressure, tropopause parameters and ionospheric total electron content (TEC) and electron density profile as well. The GNSS reflected signals from the ocean and land surface could determine the ocean height, wind speed and wind direction of ocean surface, soil moisture, ice and snow thickness. In this paper, GNSS remote sensing applications in the atmosphere, oceans, land and hydrology are presented as well as new objectives and results discussed.     

基于覆盖圆的太阳同步回归轨道卫星目标轨迹调整方法

遥感卫星星座在环境监测、地理测绘等领域运用中,需要考虑目标轨迹分布的优化问题.轨迹分布与星座的重访能力和进出站间隔保持等应用需求密切相关.目前对星下点轨迹分布的优化和调整还缺乏准确实用的方法,存在卫星数目增多带来的计算量增加问题和对多种需求综合考虑不够的问题.为了克服现有技术的不足,解决太阳同步回归轨道遥感卫星星座的目...     

Techniques for the selection of spectral intervals for multispectral survey of the earth's resources from space

A solution has been proposed for the problem of optimal selection of spectral intervals for multispectral survey of the Earth's resources from space. The problem of planning multipurpose experiments on remote sensing of environment and natural resources has been considered.     

Main results and perspectives of some Chilean experiences developed with low cost and accurate spatial remote sensing technology

This paper intends to summarize the main results and perspectives of several Chilean Programs developed by using low cost but accurate remote sensing techniques. Due to paper restrictions, three main applications will be shown : use of satellite data collection systems to measure meteorological data in Ant arctic Peninsula; study of geothermal resources in Los Andes Range by using multispectral and multitemporal Landsat images; and snowmelt runoff forecasting for Andean watersheds by using Landsat data. All these applications have allowed to obtain important and useful results and low cost, reliable and accurate methodologies have been obtained for these studies.     

光学遥感卫星在轨星上绝对辐射定标的研究进展

高精度绝对辐射定标是实现光学遥感定量化应用的重要前提。首先简要介绍了绝对辐射定标,接下来系统性地梳理国内外发展现状及发展趋势,重点分析了太阳反射谱段光学遥感卫星在轨星上绝对辐射定标的各种方法,包括遥感器上定标设备、恒星和月球定标、高精度参考交叉定标卫星和同步绝对辐射定标仪等,其中前两类已经在轨实现精度优于2%~5%,后两类计划当中精度优于1%。最后总结发展规律和发展启示,给出高精度光学遥感卫星在轨星上绝对辐射定标发展的几点讨论。     

Remote sensing of aerosol and radiation from geostationary satellites

The paper presents a high-level overview of current and future remote sensing of aerosol and shortwave radiation budget carried out at the US National Oceanic and Atmospheric Administration (NOAA) from the US Geostationary Operational Environmental Satellite (GOES) series. The retrievals from the current GOES imagers are based on physical principles. Aerosol and radiation are estimated in separate processing from the comparison of satellite-observed reflectances derived from a single visible channel with those calculated from detailed radiative transfer. The radiative transfer calculation accounts for multiple scattering by molecules, aerosol and cloud and absorption by the major atmospheric gases. The retrievals are performed operationally every 30 min for aerosol and every hour for radiation for pixel sizes of 4-km (aerosol) and 15- to 50-km (radiation). Both retrievals estimate the surface reflectance as a byproduct from the time composite of clear visible reflectances assuming fixed values of the aerosol optical depth. With the launch of GOES-R NOAA will begin a new era of geostationary remote sensing. The Advanced Baseline Imager (ABI) onboard GOES-R will offer capabilities for aerosol remote sensing similar to those currently provided by the Moderate Resolution Imaging Spectroradiometer (MODIS) flown on the NASA Earth Observing System (EOS) satellites. The ABI aerosol algorithm currently under development uses a multi-channel approach to estimate the aerosol optical depth and aerosol model simultaneously, both over water and land. Its design is strongly inspired by the MODIS aerosol algorithm. The ABI shortwave radiation budget algorithm is based on the successful GOES Surface and Insolation Product system of NOAA and the NASA Clouds and the Earth’s Radiant Energy System (CERES), Surface and Atmospheric Radiation Budget (SARB) algorithm. In all phases of the development, the algorithms are tested with proxy data generated from existing satellite observations and forward simulations. Final assessment of the performance will be made after the launch of GOES-R scheduled in 2012.     

Advances on Technology and Application of Ocean Color Remote Sensing in China (2004 - 2006)

China has great progress in the technology and application of ocean color remote sensing during 2004-2006. In this report, firstly, four major technical advances are displaying, including (1) the vector radiative transfer numerical model of coupled ocean-atmosphere system; (2) the atmospheric correction algorithm specialized on Chinese high turbid water; (3) systematical research of hyper-spectrum ocean color remote sensing; (4) local algorithms of oceanic parameters, like ocean color components, ocean primary productivity, water transparency, water quality parameters, etc. On the foundation of technical advances, ocean color remote sensing takes effect on ocean environment monitoring, with four major kinds of application systems, namely, (1) the automatic multi-satellites data receiving, processing and application system; (2) the shipboard satellite data receiving and processing system for fishery ground information; (3) Coastal water quality monitoring system, integrating satellite and airborne remote sensing technology and ship measurement; (4) the preliminary system of airborne ocean color remote sensing application system. Finally, the prospective development of Chinese ocean color remote sensing is brought forward. With Chinese second ocean color satellite (HY-1B) orbiting, great strides will take place in Chinese ocean color information accumulation and application.     

A decade of remote sensing in India — Some salient results

Remote sensing activities in India over the past decade are briefly described in the paper; some important application areas are explained. Some results are highlighted. Activities in India for building remote sensing spacecraft, sensors and ground segment are summarised. Some facilities in India for remote sensing applications including low cost interpretative equipment developed are described. The paper also outlines the Indian Remote Sensing Satellite (IRS) series, the first of which is presently under development for launch in 1986 and the National Natural Resources Management System (NNRMS) under evolution.     

基于北斗三号的长基线共视时间比对

卫星导航共视时间比对一直是远距离时间比对的重要方法之一。使用我国最新发射的北斗三号全球导航卫星，基于中科院国家授时中心（NTSC）和捷克光电研究院（TP）各自的时间产生和保持系统，开展了中捷北斗三号长基线共视时间比对试验。本文对中捷两站各自的北斗卫星可视数及其卫星高度角情况进行了统计分析，利用Vondark滤波对时间比对结果进行了降噪处理，最后将北斗三号共视时间比对结果与北斗二号及GPS共视时间比对结果进行了比较。结果表明：北斗三号在当前全球组网阶段中捷共视可视卫星数比北斗二号还少的情况下，其共视时间比对精度达到1.16ns，较北斗二号提升约19%，与GPS更为接近。     

基于嵌入式FPGA加速ORB算法的遥感影像配准方法

卫星上计算资源有限，星载嵌入式处理器处理遥感影像的配准时通常需要很长的时间。可编程逻辑门阵列（FPGA）利用其内部可编程器件可用于加速图像处理。提出了一种基于Xilinx公司的ZYNQ芯片加速ORB算法的遥感影像配准方法，可用于3000×3000像素尺寸的卫星图像配准，缩短了计算耗时，提升了ORB算法的计算能效比。利用FPGA能够实现真正的并行计算电路，实现ORB算法多支路单层流水线的并行计算结构。采用软硬件结合的方法实现架构，能够处理不同分辨率的图像，可灵活配置特征点的数量。基于设计的加速ORB配准方法，获得了较高准确率。与软件实现相比,OVS-1A遥感影像偏移精度损失低于0.05个像元;GF.4遥感影像偏移精度损失小于0.9个像元。将ORB配准算法流程应用在ZYNQ7020上，耗时减少了57.50%。