Investigation of CSAC Driven One-Way Ranging Performance for CubeSat Navigation
Investigation of CSAC Driven One-Way Ranging Performance for CubeSat Navigation
复制标题
CSAC 驱动的 CubeSat 导航单向测距性能研究
DOI：
--
复制
发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Jill Suebert
中科院分区：
文献类型：
--
作者：
Margaret M. Rybak;P. Axelrad;Jill Suebert
目前的双向卫星跟踪方法不足以支持对深空小型卫星飞行任务日益增长的兴趣。为了满足使立方体卫星如此吸引人的低成本和最小资源分配，必须开发减少地面通信要求的导航方法。一种有前途的方法是使用稳定的机载定时参考来实现单向地面上行链路测距能力。芯片级原子钟（CSAC）是一个稳定的振荡器，满足立方体卫星上使用的尺寸，重量和功率要求。麦克斯韦，一个科罗拉多大学博尔德立方体卫星使命，提供了一个机会，飞行测试CSAC驱动的单向测距。这项工作提出了一个初步的模拟的使命，建模预期的低地球轨道确定（OD）的性能使用CSAC驱动的辐射测量。热变化对CSAC行为的影响被特别考虑，并在随机时钟和热变化的存在下的OD性能进行评估。结果表明，使用动态模型补偿算法比状态噪声补偿算法更有效地减轻热时钟效应，为一秒和三十秒的数据速率。这种低地球轨道模拟和最终的麦克斯韦CSAC飞行为证明立方体卫星使用单向测距导航的可行性迈出了第一步。美国宇航局已经确定了使用立方体卫星进行深空探测的潜在科学效益。传统的深空任务依赖于双向的地球跟踪，为此，地面站必须一次将其通信能力专用于一个航天器。这种跟踪所需的时间和资源对于低成本的小型卫星飞行任务来说是不可行的。美国宇航局一直在探索单向跟踪，以消除与地球进行这种耗时的双向传输交换的需要。在这种有利的配置中，地面站可以同时上行到其视场内的所有卫星，并且卫星可以独立地执行轨迹估计。然而，该方法需要稳定的机载定时，以消除对恒定的基于地面的定时相关性的需要。为了满足这种计时要求，NASA的喷气推进实验室（JPL）开发了高稳定性的深空原子钟（DSAC）。DSAC被设计成在相对较小的卫星上飞行，使它们能够使用单向测距信号来自主测量距离并估计其轨迹。美国宇航局的一项技术演示使命（TDM）将于2018年发射，它将对地球轨道上的DSAC运行进行为期一年的监测。该TDM旨在证明DSAC的稳定性足以产生低于10米（3-sigma）的深空轨迹分辨率，与当前的双向跟踪方法相匹配。初步模拟，使用预期的DSAC稳定性能和典型的深空跟踪制度，已显示地球OD恢复到亚米级。一个火星轨道器模拟，使用DSAC驱动的单向跟踪，产生的轨道分辨率约为5米，使用X波段多普勒和1米，使用Ka波段多普勒跟踪。芯片级原子钟（CSAC）的占地面积比DSAC小得多，但代价是稳定性性能大幅下降。研究CSAC级稳定性是否能够提供立方体卫星使命导航所需的性能，需要进行模拟研究和飞行试验。科罗拉多大学博尔德分校的麦克斯韦计划于2021年发射低地球轨道（LEO）立方体卫星使命，为进行基于CSAC的单向测距的类似飞行测试提供了机会。这项使命由空军大学纳米卫星计划支持，重点是展示下一代通信能力。CSAC将被集成到麦克斯韦通信系统中，以证明其支持测距的潜在效用。CSAC将驱动X波段下行链路信号的生成，并将在地面上进行辐射测量。这种下行链路而不是上行链路配置允许对基本CSAC驱动的单向测距概念进行早期测试，同时保持在主要麦克斯韦使命的约束范围内。从下行链路数据形成地面上的观测消除了开发机载系统来处理上行链路地面信号的需要。这种上行链路配置超出了使命的范围，
Current two-way satellite tracking methods are insufficient to support the growing interest in deep space small satellite missions. To meet the low cost and minimal resource allocations that make CubeSats so appealing, navigation methods must be developed that reduce ground communication requirements. One promising approach is the use of a stable onboard timing reference to enable one-way ground uplink ranging capabilities. The Chip Scale Atomic Clock (CSAC) is a stable oscillator that meets the size, weight, and power requirements for use on CubeSats. Maxwell, a University of Colorado Boulder CubeSat mission, provides the opportunity for a flight test of CSAC-driven one-way ranging. This work presents a preliminary simulation of the mission, modeling the expected LEO orbit determination (OD) performance using CSAC-driven radiometric measurements. The effect of thermal variations on the CSAC behavior are specifically considered, and the OD performance in the presence of both stochastic clock and thermal variations is evaluated. It is shown that the use of a Dynamic Model Compensation algorithm is more effective than a State Noise Compensation algorithm in mitigating the thermal clock effects, for both one second and thirty second data rates. This LEO simulation and eventual Maxwell CSAC flight provide the first steps towards demonstrating the feasibility of CubeSat navigation using one-way ranging. INTRODUCTION NASA has identified the potential scientific benefit of using CubeSats for deep space exploration. Conventional deep space missions rely on two-way Earth based tracking, for which ground stations must dedicate their communication capabilities to one spacecraft at a time. The time and resources required for such tracking is not feasible for low-cost, small satellite missions. NASA has been exploring one-way tracking to eliminate the need for such time-consuming two-way transmission exchanges with Earth. In this favorable configuration ground stations can uplink to all satellites within their field of view at the same time, and the satellites can perform trajectory estimation independently. However, this method requires stable onboard timing to eliminate the need for constant ground based timing correlation. To address this timekeeping requirement, NASA’s Jet Propulsion Laboratory (JPL) has developed the highlystable Deep Space Atomic Clock (DSAC). DSAC is designed to be flown on relatively small satellites, enabling them to use one-way ranging signals to autonomously measure range and estimate their trajectories. A NASA Technology Demonstration Mission (TDM), to launch in 2018, will monitor the operation of a DSAC in Earth orbit for one year. This TDM seeks to demonstrate DSAC stability sufficient to yield deep space trajectory resolution below 10 meters (3-sigma), matching that of current two-way tracking methods. Preliminary simulations, using the expected DSAC stability performance and a typical deep space tracking regime, have shown Earth OD recovery to submeter levels. A Mars orbiter simulation, using DSAC driven one-way tracking, yielded orbit resolution to approximately 5 meters using X-band Doppler and 1 meter using Ka-Band Doppler tracking. The Chip Scale Atomic Clock (CSAC) has a significantly smaller footprint than DSAC, but at the cost of substantially degraded stability performance. Investigating if CSAC-level stability can provide the performance necessary for CubeSat mission navigation, requires both simulation studies and flight experiments. Maxwell, a University of Colorado Boulder low Earth orbit (LEO) CubeSat mission, with planned launch in 2021, provides the opportunity to conduct a similar flight test of CSAC-based one-way ranging. This mission, supported by the Air Force University Nanosat Program, is focused on demonstrating next generation communication capabilities. A CSAC will be integrated into the Maxwell communications system to demonstrate its potential utility to support ranging. The CSAC will drive the generation of the X-band downlink signal, from which radiometric measurements will be made on the ground. This downlink rather than uplink configuration, allows for an early test of the basic CSAC-driven oneway ranging concept, while remaining within the constraints of the primary Maxwell mission. Forming the observations on the ground from the downlinked data removes the need to develop an onboard system to process an uplinked ground signal. Such an uplink configuration is beyond the scope of the mission and