典型卫星轨道的位移损伤剂量计算与分析

位移损伤剂量是评估电子元器件在轨发生位移损伤导致性能退化的重要参数。文章首先给出了位移损伤剂量的等效原理和计算方法,即用位移损伤等效注量来表征卫星轨道带电粒子导致的位移损伤剂量;之后分别采用3种不同的太阳质子注量模型,计算了典型大椭圆轨道的位移损伤等效注量,并结合计算结果对不同模型的特点和适用性进行了分析;其后针对4种典型卫星轨道,计算了不同飞行寿命期内的位移损伤等效注量,发现不同轨道的位移损伤剂量有较大差异,并结合空间带电粒子辐射环境分布特点及卫星轨道参数等分析了差异的产生原因;最后,分析不同的太阳质子注量预估方法对位移损伤剂量计算结果的影响,总结了不同轨道、不同飞行寿命情况下卫星经受的带电粒子辐射环境的严酷程度。研究结果可为卫星内部元器件位移损伤效应防护工作提供参考。     

Capabilities of Kinematically Regular Satellite Systems with Symmetry Groups of the Second Type in the Problem of Continuous Single Coverage of the Earth

The problem of a continuous single coverage of the Earth by systems of satellites in circular orbits of equal radii is considered. The results of calculating the characteristics of kinematically regular systems consisting of 6 to 60 satellites and possessing symmetry groups of the second type are presented. It is shown that, when the number of satellites varies from 20 to 38 inclusive, the best systems of this class surpass all currently known systems with respect to their characteristics.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 3, 2005, pp. 215–223.Original Russian Text Copyright © 2005 by Mozhaev.     

翼伞归航准则及测风原理探讨

翼伞作为一种新型气动力减速器日渐受到空间回收技术重视。文中给出了具有非比例自动归航控制的翼伞系统的归航准则(考虑到风的影响)以及利用GPS测量数据计算风场的公式。     

High-Precision Space Astrometry of Gamma-Ray Bursts: II. Relativistic Corrections in Converting the Time Scales

A technique for the determination of cosmic gamma-ray burst coordinates by measuring the time lag between gamma-ray burst signals on different spacecraft in the near-Sun orbits is developed. On the basis of the well-known relativistic time transformation between barycentric, geocentric, and instrumental coordinate frames of reference, the time corrections for specific spacecraft systems are calculated. Among various relativistic corrections, those are determined that are significant for the method in question.     

Optimization of the trajectory of the spacecraft insertion into the system of heliocentric orbits

The possibility of the spacecraft insertion into the system of operational heliocentric orbits has been analyzed. It has been proposed to use a system of several operational heliocentric orbits. On each orbit, the spacecraft makes one or more revolutions around the Sun. These orbits are characterized by a relatively small perihelion radius and relatively high inclination, which allows one to investigate the polar regions of the Sun. The transition of the spacecraft from one orbit to another has been performed using an unpowered gravity assist maneuver near Venus and does not require the cruise propulsion operation. Each maneuver transfers the spacecraft into the sequence of operational heliocentric orbits. We have analyzed several systems of operational heliocentric orbits into which the spacecraft can be inserted by means of the considered transportation system with electric propulsion (EP). The mass of the spacecraft delivered to these systems of operational orbits has been estimated.     

Calculation and Study of Limited Orbits around the <Emphasis Type="Italic">L</Emphasis><Subscript>2</Subscript> Libration Point of the Sun–Earth System

A procedure has been proposed for calculating limited orbits around the L₂ libration points of the Sun–Earth system. The motion of a spacecraft in the vicinity of the libration point has been considered a superposition of three components, i.e., decreasing (stable), increasing (unstable), and limited. The proposed procedure makes it possible to correct the state vector of the spacecraft so as to neutralize the unstable component of the motion. Using this procedure, the calculation of orbits around various types of libration points has been carried out and the dependence on the orbit type on the initial conditions has been studied.     

A new universal equation for the time of transfer between two points of the central gravitational field

The paper presents the derivation of two new equations for calculating the time of transfer between two points of the central gravitational field: for hyperbolic orbits and the universal equation for elliptical and hyperbolic orbits. In the paper we have used as an independent variable, instead of the linear elements (semimajor axis, focal parameter of orbit or a chord connecting the ends of boundary radii of transfer), the angular parameter—the angle between the radius vector of an initial point of transfer and the vector of initial velocity of transfer. Paper’s material is a continuation of that presented in the “Space research“ Journal, vol. 2, March–April, 2009.     

邻近近圆轨道两个飞行器的最优交会

邻近近圆轨道上两个飞行器的相对运动可以用线性化Ｃ—Ｗ方程描述。本文利用线性化Ｃ—Ｗ方程研究了常推力作用下两个飞行器的固定时间最省燃料交会问题，给出了最优推力作用的开关函数和最优推力方向的计算方法。     

A vector method for synthesis of orbits and the structure of satellite constellations for multiswath periodic coverage of the Earth

Single satellites and multisatellite constellations for the periodic coverage of the Earth are considered. The main feature is the use of several cameras with different swath widths. A vector method is proposed which makes it possible to find orbits minimizing the periodicities of coverage of a given area of Earth uniformly for all swaths. Their number is not limited, but the relative dimensions should satisfy the Fibonacci series or some new numerical sequences. The results apply to constellations of any number of satellites. Formulas were derived for calculating their structure, i.e., relative position in the constellation. Examples of orbits and the structure of constellations for the Earth’s multiswath coverage are presented.     

Controlling the motion of a spacecraft when approaching a large object of space debris

The problem of calculating the parameters of maneuvering a spacecraft as it approaches a large object of space debris (LOSD) in close near-circular noncoplanar orbits has been considered. In [1–4], the results of analyzing the problem of the flyby of the separated LOSD groups have been presented. It has been assumed that a collector spacecraft approaches the LOSD and captures it or it is inserted into the nozzle of a small spacecraft that has a proper propulsion system (PS). However, in these papers, the flight from one object to another was only analyzed and the problem of approaching to LOSD with a given accuracy was not considered. This paper is a supplement to the cycle of papers [1–4]. It is assumed that, the final stage of approaching the LOSD is implemented by maneuvering in many orbits (up to several dozens) with low-thrust engines, but the PS operating time is fairly small compared with the orbit period in order to make it possible to use impulse approximation in the calculations.