星下点

基于OpenGL的卫星星下点轨迹可视化仿真

Visual Simulation of the Track of Sub-Satellite Point by Using OpenGL

位于类GPS卫星星座时，与中轨道探测器探测星下点基本相同，不会影响光辐射辐照度的探测和爆炸当量的确定。

Detection of the irradiance and the power would not be effected when the detector on the ISGO or similar GPS constellation .

计算了到达探测器靶面上目标和背景的光谱辐照度。位于类GPS卫星星座时，与中轨道探测器探测星下点基本相同，不会影响光辐射辐照度的探测和爆炸当量的确定。

The target and background irradiance that can arrive at the detector 's target plane were computed . Detection of the irradiance and the power would not be effected when the detector on the ISGO or similar GPS constellation .

针对J2项摄动的LEO卫星与地面站通信链路，提出一种由偏近点角的超越方程计算时间窗口的新方法，采用以大圆近似星下点轨迹的方法求解此方程。

A transcendental equation about the eccentric anomaly is proposed to compute the time windows between the J2 perturbed LEO satellite and the ground station , and this equation is solved by using the great circle to locally approximate the ground trace .

其中着重讨论了脉冲重复频率（PRF）的选择、它与多普勒带宽的关系、发射干扰与星下点干扰的影响、距离模型、方位模型、地面测绘带宽、数据传输速率等问题。

The most important factors in the design are related with the selection of Pulse Repeating Frequency ( PRF ), Doppler bandwidth , transmit and nadir interference restriction , range and azimuth ambiguity , ground swath , data transfer rate etc.

根据GEO卫星的线性化状态转移方程，通过设定地面跟踪网坐标和卫星星下点经度计算叠加矩阵，由观测弧长和采样间隔直接计算定轨精度评定公式中的主要部分。

The superposition matrix was computed by setting coordinate of ground tracking net and satellite ground longitude according to the linear state transfer equation of GEO satellite . The main part of the evaluation equation for orbit determination accuracy was calculated by observation arc and sampling interval .

首先给出考虑J2摄动项时近地轨道卫星的轨道模型、星下点计算方法和覆盖判断准则，在此基础上给出一种近地回归轨道的迭代设计方法。

The orbit models , the calculation methods of sub satellite and the coverage judgement which take into account the J 2 perturbations are given first , and then an iterating methods of designing satellite orbit with repeat ground trace is proposed .

用同样的约束回归算法对AMSU偏离星下点的观测视场作了临边订正，对于通道4~14（频率52.8~57.29GHz）的大气探测通道，使其最大偏差由-15~5K减小为±0.9K。

By the same algorithm a limb adjustment is made off the sub-satellite point in the fields of view . For atmospheric sounding channels 4 ~ 14 ( frequencies of 52.8 ~ 57.29 GHz ) the maximum deviation is thereby decreased to ± 0.9 K from - 15 ~ 5 K.

结果表明，当采用近星下点的AMSU-A亮温资料样本时，该算法模型具有较高的反演精度，在100hPa以下，温度均方根偏差为0.4K，100hPa及以上的均方根偏差为1.0K。

Results show that when AMSU samples at the sub-satellite point are adopted , the constrained regression algorithm yields higher retrieval accuracy with the root-mean-square error of ( 0.4 K ) ( 1.0 K ) below ( at and above ) 100 hPa .

星下点轨迹为∞字形同步卫星轨道的实现及应用

Design and application of synchronous orbit with ground track of "∞"

继而给出星下点最小凸球面多边形的判定算法；

An algorithm of determining the minimum convex spherical polygon is presented .

一类由星下点反算卫星近圆回归轨道的方法

Calculation Method of a Kind of Near-round Repeating Satellite Orbit Using Nadir Points

该套软件根据卫星轨道调整前后的轨道参数特点和轨道调整后的星下点轨迹要求，确定机动时间，将调整轨道半长轴与微调星下点轨迹结合起来，在最短时间内完成轨道调整任务。

The software determines maneuver time by considering the adjustment of semi-major axis and ground track .

算法利用大圆弧近似可视窗口内的星下点轨迹获得可见性结果。

The great circle arc is used to approximate the sub-satellite track within the visibility window .

使用等距墨卡托投影，将卫星的星下点轨迹绘制在地球平面图上。

The track of sub-satellite points are drawn on the ichnography of the earth with the projection of Mercator .

作为星下点分布的一维量度，星间角距可由参照轨道要素解析地表达。

The mean angular separation can be formulated by reference orbital elements as a one-dimensioned measure of subpoints distribution .

轨道维持的任务是将卫星的星下点轨迹保持在设计的参考轨迹附近。

The ground tracks of satellites required for mission should be maintained close to those of reference orbits over the lifetime of satellites .

实现了在全球卫星影像地图上卫星的星下点轨迹的绘制和显示，以及覆盖区域的显示；

Realize the render and display of subastral point tracks on the global satellite images . Also include the display of satellite coverage ;

阐述了基本轨道应用分析理论，包括星下点轨迹计算、可见性分析、覆盖评估和轨道寿命估算。

Expatiated on the application theory of basic orbit , including subastral point calculation , visibility analysis , coverage evaluating and spacecraft life-span estimate .

分析结果表明：用实测星下点统计计算得到的卫星东西漂移加速度和卫星同步半径与理论计算有较好的一致性。

The analysis has shown that the results got both from theoretical calculation and analysis of the data from TT & C equipment are well consistent .

扫描偏差是临边测量相对于星下点测量的系统偏差，统计显示该种偏差具有一定的纬度依赖性，所以订正时按每10度的纬度带分别进行订正。

Scan bias is a relative bias between limb and nadir measurements and corrected for each latitude band of 10 degrees due to its statistically latitudinal dependency .

提出了一类近圆回归轨道的设计方法，解决当飞行任务对星下点有要求时，近圆回归轨道的设计问题。

A method of nearly-round repeating orbit designing is proposed . It 's aimed to resolve the question of orbit designing with the restriction of a specific satellite ground trace .

以轨道半径和轨道倾角为未知量依据星下点轨迹要求条件构建了非线性方程组，但直接求解过于复杂，采取迭代的方法解决。

Non-linear equations are ( constructed ) with the restriction of the satellite ground trace to resolve the unknown semi-axis and inclination , but it 's too complicated to be resolved directly .

太阳同步轨道的主要特点是卫星在任一时刻其星下点的阳光条件基本相同，这对卫星上对地仪器的工作是非常有利的。

The distinct trait of sun synchronic orbit satellite is that there will be the same sun conditions in the subpoint of the satellite wherever the satellite is , it benefits the earth reference equipments .

轨道偏离赤道平面的同步卫星，其星下点（或视位置）的口漂移轨迹址对称于静止位置的8字形。

When the geostationary satellite orbit deviates from equatorial plane , the day-drift trace of it 's sub-satellite point ( or apparent place ) is a " 8 " - shape pattern symmetrical about the stationary position .

植被指数基本上不依赖于卫星观测角，但观测区处在星下点附近时测得的植被指数值要比远离星下点时大一些。

Vegetation index is generally independent of the satellite observing angles , but for the same region , the vegetation indexes derived when the region is near the sub-satellite point are a little higher than those derived when the region is far from the sub-satellite point .

快速算法通过分析中继卫星与客户星通信链路的几何特性建立了三类可视球冠模型，采用以大圆近似星下点轨迹的方法计算时间窗口。

In the fast algorithm , the models of three types of visibility spherical caps are established by analyzing the communication links between the relay satellites and the user satellites . By using the circle locally approximation to the ground trace , the time windows are estimated .