Resourcesat-1 mission planning,analysis and operations—Outline of key components

Resourcesat-1 is a global mission which provides continuity to the earth resources monitoring missions earlier launched by India. Resourcesat-1 is designed to have an improvement in the payload camera characteristics providing multi-spectral imaging capability in high resolution. This paper provides an overview of mission planning and analysis aiding spacecraft configuration, pre-launch simulations and operations, early-orbit operations and the on-orbit operational guidelines for Resourcesat-1. Mission planning involved integrating and inter-relating the efforts of space and ground systems in realizing the operational system which provides the continuity of satellite-based remote sensing data to the user community. Mission analysis related to contiguous imaging requirement of LISS-4 payload, resulted in a spacecraft yaw steering during imaging operations. Pre-launch simulation involved development of a software spacecraft simulator to be used as a tool for network tests, training of spacecraft operation personnel and validating the spacecraft health monitoring software. The required operations that were performed on the spacecraft to characterize and establish the on-orbit configuration for the normalization of daily operations are addressed in the sections relating to early orbit operations and on-orbit operational guidelines.     

网络、通讯设备的抗震试验考核

鉴于网络、通讯设备的安全性能变得日益重要,介绍了网络、通讯设备的抗地震试验方法,并着重于介绍美国的抗震试验标准及抗震试验的一般要求。     

GNSS导航信号仿真中运动轨迹设计

GNSS信号仿真器模拟GNSS信号时需要提供轨迹数据,要求轨迹数据连续、平滑且二阶可导。要满足上述条件,传统的方式通常是对轨迹进行分段仿真,设置仿真轨迹的时候较为复杂,在仿真高动态载体时,还常常会出现轨迹不平滑的现象。为此提出采用三次样条插值的方法来仿真载体轨迹,既满足GNSS信号仿真器对轨迹数据的要求,又保证与真实轨迹的相似性。     

Using centrifuge tests data to identify the dynamic soil properties: Application to Fontainebleau sand

Knowledge of the dynamic properties of the soil is of great importance as the dynamic shear modulus and damping ratio are necessary input data in finite element modeling programs. This paper presents a post-processing strategy to identify the shear modulus and damping ratio vs. shear strain curves using the experimental results of a dynamic centrifuge program. Application is presented for the Fontainebleau sand. The proposed methodology is fast, robust and able to capture the nonlinear hysteretic behavior of the material. Based on the results, specific parameters for the Fontainebleau sand are identified for the empirical equation of shear modulus and damping ratio proposed by Ishibashi and Zhang [1]. It is found that confining pressure has an important influence on both shear modulus evolution and damping ratio.     

Soil and water losses from new citrus orchards growing on sloped soils in the western Mediterranean basin

Ten representative research sites were selected in eastern Spain to assess soil erosion rates and processes in new citrus orchards on sloping soils. The experimental plots were located at representatives sites on limestone, in areas with 498 to 715 mm year^?1 mean annual rainfall, north‐facing slopes, herbicide treated, and new (less than 3 years old) plantations. Ten rainfall simulation experiments (1 h at 55 mm h^?1 on 0·25 m² plots) were carried out at each of the 10 selected study sites to determine the interill soil erosion and runoff rates. The 100 rainfall simulation tests (10 × 10 m) showed that ponding and runoff occurred in all the plots, and quickly: 121 and 195 s, respectively, following rainfall initiation. Runoff discharge was one third of the rainfall, and sediment concentration reached 10·4 g L^?1. The soil erosion rates were 2·4 Mg ha^?1 h^?1 under 5‐year return period rainfall thunderstorms. These are among the highest soil erosion rates measured in the western Mediterranean basin, similar to badland, mine spoil and road embankment land surfaces. The positive relationship between runoff discharge and sediment concentration (r² = 0·83) shows that the sediment availability is very high. Soil erosion rates on new citrus orchards growing on sloped soils are neither tolerable nor sustainable. Copyright © 2009 John Wiley & Sons, Ltd.     

海潮引起的滨海地区包气带气压周期性变化的数值模拟

滨海地区的地下水位由于海潮而上下波动, 这早已是为人熟知的事实.但是, 滨海地区包气带中气压也会随海潮的起伏而作周期性变化, 这一点却很少为人注意.如果地表由渗透性差的材料如水泥或沥青路面覆盖(这种情况在香港高度城市化的近海地区很常见), 海潮的起伏会产生幅度异常高的气压波动.在某些情形下, 足够高的气压会引起如路面拱起等工程问题.因此, 研究海潮引起的包气带气流, 不仅具有理论意义, 还对滨海地区土木工程有实际指导作用.以香港某滨海地区为例, 建立了该地区一剖面上水气两相流的二维数学模型, 并用TOUGH2程序进行了数值模拟.通过数值敏感度分析, 探讨了影响沥青路面下气压的主要水文地质因素.在根据该地区实际水文地质情况选取了适当的模型边界条件和模型参数后, 沥青路面下气压的数值模拟结果和观测数据吻合程度良好.      

Rill length and plot‐scale effects on the hydrogeomorphologic response of gravelly roadbeds

Although unpaved roads are well‐recognized as important sources of Hortonian overland flow and sediment in forested areas, their role in agriculturally‐active rural settings still lacks adequate documentation. In this study, we assessed the effect of micro‐catchment size, slope, and ground cover on runoff and sediment generation from graveled roadbeds servicing a rural area in southern Brazil. Fifteen replications based on 30‐min‐long simulated rainfall experiments were performed at constant rainfall intensities of 22–58 mm h^?1 on roadbeds with varying characteristics including ~3–7 m² micro‐catchment areas, 2–11° slopes, 2–9.7‐m‐long shallow rill features, and 30–100% gravel cover. The contributions of micro‐catchment size and rill length were the most important physical characteristics affecting runoff response and sediment production; both the size of the micro‐catchment and the length of the rills were inversely related to sediment loss and this contradicts most of the rill erosion literature. The effect of micro‐catchment size on runoff and sediment response suggests a potentially problematic spatial‐scale subjectivity of experimental plot results. The inverse relationship between rill length and sediment generation is interpreted here as related to the predominance of coarse fragments within rills, the inability of the shallow flows generated during the simulations to erode this sediment, and their role as zones of net sediment storage. Copyright © 2015 John Wiley & Sons, Ltd.     

福建省森林生态系统NPP的遥感模拟与分析

利用MODIS遥感影像,结合气象资料等数据,采用BEPS过程模型对2004年福建省的森林生态系统植被净初级生产力(NPP)进行了模拟验证。研究结果表明,2004年福建省森林生态系统NPP平均值为578.97gC/m²·a,NPP总量累计达到46.18×106tC;不同林地NPP全年平均值大小依次为:竹林≈阔叶林>杉木>马尾松,其值分别为:788.6gC/m²·a,780.0gC/m²·a,519.8gC/m²·a,437.3gC/m²·a;时空分析结果表明,2004年6-8月NPP形成较为明显的坑形分布形态,主要的原因之一很可能是有效降水量偏少;在空间分布上,福建省森林生态系统NPP与海拔高程显著相关,体现了该地区森林生态系统NPP空间分布的地域特征,这在一定程度上表明随着海拔上升,山高坡陡,人类对森林生态系统的干扰活动减少,有助于森林生态系统生产力的提高和维持。最后,分析了应用BEPS过程模型模拟福建省森林生态系统净初级生产力的不确定性问题。     

基于新型中压堵漏试验仪的堵漏试验研究

堵漏试验仪是制定防漏堵漏技术方案的关键实验设备之一。针对现有堵漏试验仪普遍存在的结构复杂、试验流程繁冗、浆液用量较大、数据重现性较差等问题,设计了一种中压（试验压力为0～1 MPa）堵漏试验仪。该装置能模拟1～3 mm的条缝型漏失地层和1～4 mm的孔洞型漏失地层,封板（缝板和孔板）的实际漏失面积为0.35～2.79 cm2,孔隙率1.81%～14.24%。基于该试验装置,获取了由膨胀堵漏剂、核桃壳等组成的适于不同漏失地层的堵漏浆液配方。研究发现,堵漏浆液的封堵效果不仅取决于裂缝或孔洞的大小,也要考虑其孔隙率。该堵漏仪及堵漏浆液配方可为钻井防漏堵漏工作提供有益参考。