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首页> 外文期刊>Journal of Guidance, Control, and Dynamics >Extension of the Sun-Synchronous Orbit
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Extension of the Sun-Synchronous Orbit

机译：太阳同步轨道的扩展

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THROUGH careful consideration of the orbit perturbation forcendue to the oblate nature of the primary body a secular variationnof the ascending node angle of a near-polar orbit can be inducednwithout expulsion of propellant. Resultantly, the orbit perturbationsncan be used to maintain the orbit plane in, for example, a nearperpendicularn(or at any other angle) alignment to the sun linenthroughout the full year of the primary body; such orbits are normallyntermed sun-synchronous orbits [1,2]. Sun-synchronous orbits aboutnthe Earth are typically near-circular low Earth orbits (LEOs), with annaltitude of less than 1500 km. It is normal to design an LEO such thatnthe orbit period is synchronized with the rotation of the Earth’snsurface over a given period, such that a repeating ground track isnestablished. A repeating ground track, together with the nearconstantnillumination conditions of the ground track when observednfrom a sun-synchronous orbit, enables repeat observations of a targetnover an extended period under similar illumination conditions [1,2].nFor this reason, sun-synchronous orbits are extensively used by Earthnobservation (EO) platforms, currently including the EnvironmentalnSatellite (ENVISAT), the second European Remote Sensing satelliten(ERS-2), and many more.nBy definition, a given sun-synchronous orbit is a finite resourcensimilar to a geostationary orbit.Atypical characterizing parameter ofna sun-synchronous orbit is the mean local solar time (MLST) atndescending node, with a typical value of 1030 h. Note that ERS-1 andnERS-2 use an MLST at descending node of 1030 h u00025 min, whilenENVISAT uses a 1000 h u00025 min MLST at descending node [3].nFollowing selection of the MLSTat descending node and for a givenndesired repeat ground track, the orbit period and hence the semimajornaxis are fixed; thereafter, assuming a circular orbit is desired, it isnfound that only a single orbit inclination will enable a sunsynchronousnorbit [2]. As such, only a few spacecraft can populate angiven repeat-ground-track sun-synchronous orbit without compromise:nfor example, on the MLST at descending node. Indeed, annotable feature of ongoing studies by the ENVISAT Post LaunchnSupport Office is the desire to ensure sufficient propellant remains atnend of mission for reorbiting to a graveyard orbit to ensure that thenorbital slot is available for future missions [4].nAn extension to the sun-synchronous orbit is considered usingnan undefined, non-orientation-constrained, low-thrust propulsionnsystem. Initially, the low-thrust propulsion system will be considerednfor the free selection of orbit inclination and altitude while maintainingnthe sun-synchronous condition. Subsequently, the maintenancenof a given sun-synchronous repeat ground track will benconsidered, using the low-thrust propulsion system to enable the freenselection of orbit altitude. An analytical expression will be developednto describe these extensions before then validating the analyticalnexpressions within a numerical simulation of a spacecraft orbit.nFinally, an analysis will be presented on transfer and injectionntrajectories to these orbits
机译：通过仔细考虑轨道的摄动力，由于基体的扁圆特性，可以在不排出推进剂的情况下引起近极轨道的上升节角的长期变化。结果，在整个基体的整个一年中，轨道扰动都可以用来使轨道平面保持与太阳亚麻布的垂直（例如，垂直）（或成任何其他角度）。这样的轨道通常称为太阳同步轨道[1,2]。围绕地球的太阳同步轨道通常是近圆形的低地球轨道（LEO），年线小于1500公里。通常将LEO设计为使轨道周期与给定周期内地球表面的旋转同步，从而建立重复的地面轨迹。从太阳同步轨道观察时，重复的地面轨道以及近乎恒定的地面照明条件使得能够在类似的光照条件下长时间观察目标物[1,2]。n因此，太阳同步轨道是被地球观测（EO）平台广泛使用，目前包括“环境卫星”（ENVISAT），第二颗欧洲遥感卫星（ERS-2）等。根据定义，给定的太阳同步轨道是与地球同步轨道类似的有限资源太阳同步轨道的典型特征参数是平均本地太阳时间（MLST）上升节点，典型值为1030 h。请注意，ERS-1和nERS-2在1030 h u00025 min的下降节点上使用MLST，而nENVISAT在下降节点[3]处使用1000 h u00025 min的MLST。n在选择MLSTat下降节点和给定的重复地面轨迹时，轨道周期和半主轴是固定的；此后，假设需要一个圆形轨道，则发现只有一个轨道倾斜将启用太阳同步轨道[2]。这样一来，只有少数航天器可以毫不妥协地填充安格文复地轨道太阳同步轨道：例如，在降落节点的MLST上。确实，ENVISAT发射后支持办公室正在进行的研究的一个显着特点是希望确保在任务执行时仍留有足够的推进剂，以便重新进入墓地轨道以确保将来的任务可以使用轨道槽[4]。同步轨道被认为是使用一种未定义的，不受方向限制的低推力推进系统。最初，将考虑使用低推力推进系统自由选择轨道倾角和高度，同时保持太阳同步状态。随后，将考虑使用低推力推进系统对给定的太阳同步重复地面轨道进行维护，以自由选择轨道高度。在验证航天器轨道的数值模拟中的分析表达式之前，将开发一个解析表达式来描述这些扩展。最后，将对这些轨道的转移和注入轨迹进行分析。

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