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331.
目标信号和雷达天线之间的极化失配,导致接收机输出的误差信号电压中除基波正规分量外,还包含基波交叉分量和二次谐波分量等,降低了测角精度。通过对线极化目标信号和椭圆极化雷达天线匹配情况的分析和计算,获得了有关的公式和曲线。还对椭圆极化目标信号和椭圆极化雷达天线情况作了阐述。公式和曲线可作为选定卫星天线或地面站雷达天线椭圆极化率的参考依据。 相似文献
332.
Orbital debris environment models are essential in predicting the characteristics of the entire debris environment, especially for altitude and size regimes where measurement data is sparse. Most models are also used to assess mission collision risk. The IDES (Integrated Debris Evolution Suite) simulation model has recently been upgraded by including a new sodium–potassium liquid coolant droplet source model and a new historical launch database. These and other features of IDES are described in detail. The accuracy of the IDES model is evaluated over a wide range of debris sizes by comparing model predictions to three major types of debris measurement data in low Earth orbit. For the large-size debris population, the model is compared with the spatial density distribution of the United States (US) Space Command Catalog. A radar simulation model is employed to predict the detection rates of mid-size debris in the field of view of the US Haystack radar. Finally, the small-size impact flux relative to a surface of the retrieved Long Duration Exposure Facility (LDEF) spacecraft is predicted. At sub-millimetre sizes, the model currently under-predicts the debris environment encountered at low altitudes by approximately an order of magnitude. This is because other small-size debris sources, such as paint flakes have not yet been characterised. Due to the model enhancements, IDES exhibits good accuracy when predicting the debris environment at decimetre and centimetre sizes. Therefore, the validated initial conditions and the high fidelity future traffic model enables IDES to make long-term debris environment projections with more confidence. 相似文献
333.
为了计算复杂目标的雷达散射截面(RCS),提出了一种基于AutoCAD几何建模的近场目标电磁散射计算技术,计算了单元体,组成体以及飞机的近场雷达散射截面,理论计算和实测结果较为吻合,为在微机上计算复杂目标近场RCS提供了一种理想的方法。 相似文献
334.
介绍了风云一号(FY-1)C,D极轨气象卫星空间粒子成分监测器的任务目标、主要功能和工程指标。以及数据的获取和处理方法。给出了空间环境宁静期、地磁扰动事件、太阳质子事件、与太阳活动的关系和粒子长期变化等探测结果,并进行了相应的分析。对C,D星空间粒子成分监测器分别进行的5年和第二次在轨测试结果表明,两星监测器工作正常、性能稳定,探测数据可靠。 相似文献
335.
基于地球扁率红外地平仪测量值修正算法研究 总被引:4,自引:0,他引:4
根据对地球扁率引起红外地平仪测量值误差修正算法进行了研究,椭球地球模型矢量投影关系得到了地球扁率修正函数和姿态角计算公式。由于地平穿越点由地球表面方程、地平平面方程和扫描圆锥锥面方程唯一确定,采用了递推方法解算出地平穿越点处的几何量,所得结果通过扁率修正函数对姿态角进行实时修正。所提算法简单,易于星载计算机在线实现,仿真算例验证了该方法的有效性。 相似文献
336.
Small satellites have captured a continuously increasing share of the market in the fields of science, technology and recently also in the telecommunications and Earth observation areas. User requirements and market opportunities for space based satellite systems for Earth observation products have grown substantially in the past decade. Criteria for the utilization of different classes of satellite systems (small and large) and analogies to developments in other areas, e.g. the telecommunications field are discussed. The end to end character of service and product oriented systems as key criteria for market success in the scientific, applications and commercial areas is underlined. Recent developments in the global change, the Earth observation applications and commercial sectors are reviewed and compared. Opportunities for small satellites in the field are related to technology advancements, cost reduction options, and progress in the state of the art in system design. 相似文献
337.
We have conducted a series of low-velocity impact experiments to understand the dispersion properties of fragments newly created by low-velocity impacts possible in space, especially in geostationary Earth orbit. The test results are utilized to establish a mathematical prediction model to be used in debris generation and propagation codes. Since the expected collision velocity between catalogued objects in geostationary Earth orbit shows a peak at a few hundreds meters per second, these impact experiments were conducted at a velocity range lower than 300m/s. As a typical structure of satellites in geostationary Earth orbit, thin aluminum honeycomb sandwich panels with carbon fiber reinforced plastics face sheets were prepared, while the projectile was a stainless steel ball of 9mm diameter. The data collected through these impact experiments have been re-analyzed based on the method used in the National Aeronautics and Space Administration (NASA) standard breakup model 1998 revision. The results indicate that the NASA standard breakup model derived from hypervelocity impacts could be applied to low-velocity collision possible in geostationary Earth orbit with some modifications. 相似文献
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340.
S. Dewitte L. Gonzalez N. Clerbaux A. Ipe C. Bertrand B. De Paepe 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(11):1906-1913
The Geostationary Earth Radiation Budget (GERB) instrument is the first to measure the earth radiation budget from a geostationary orbit. This allows a full sampling of the diurnal cycle of radiation and clouds – which is important for climate studies, as well as detailed process studies, e.g. the lifecycle of clouds or particular aerosol events such as desert storms. GERB data is now for the first time released as Edition 1 data for public scientific use. In this paper we summarise the algorithms used for the Edition 1 GERB data processing and the main validation results. Based on the comparison with the independent CERES instrument, the Edition 1 GERB accuracy is 5% for the reflected solar radiances and 2% for the emitted thermal radiances. 相似文献