基于Cubesat平台的874 GHz冰云探测仪设计

冰云探测对气候预测有重要价值,但因冰云粒子的影响,传统气象观测方法很难有效观测气候。太赫兹波的信号带宽较宽、波束较窄,在冰云探测上比使用微波毫米波更具优势。太赫兹冰云探测仪作为被动接收设备,具有体积小、功耗小的特点,与成本低、研发周期短、可以实现组网观测的Cubesat卫星平台有较高的契合度。以冰云探测为背景,分析太赫兹冰云探测仪系统指标,设计874GHz接收机系统的链路。在确保接收机系统性能的同时注重简化链路,减少体积功耗,以适应Cubesat平台,并结合工程经验在链路设计时采取预留增益余量、加入隔离器增强匹配等措施保证工程上的可实现性。最后对接收机链路进行ADS仿真,仿真结果能够满足冰云探测仪对接收机指标的需求。

The alternative of CubeSat-based advanced infrared and microwave sounders for high impact weather forecasting

The advanced infrared(IR) and microwave(MW) sounding systems have been providing atmospheric sounding information critical for nowcasting and improving weather forecasts through data assimilation in numerical weather prediction. In recent years, advanced IR and MW sounder systems are being proposed to be onboard CubeSats that are much more cost efficient than traditional satellite systems. An impact study using a regional Observing System Simulation Experiment on a local severe storm(LSS) was carried out to evaluate the alternative of using advanced MW and IR sounders for high-impact weather forecasting in mitigating the potential data gap of the Advanced Technology Microwave Sounder(ATMS) and the Cross-track Infrared Sounder(CrIS) on the Suomi-NPP(SNPP) or Joint Polar Satellite System(JPSS). It was found that either MicroMAS-2 or the CubeSat Infrared Atmospheric Sounder(CIRAS) on a single CubeSat was able to provide a positive impact on the LSS forecast, and more CubeSats with increased data coverage yielded larger positive impacts.MicroMAS-2 has the potential to mitigate the loss of ATMS, and CIRAS the loss of CrIS, on SNPP or JPSS, especially when multiple CubeSats are launched. There are several approximations and limitations to the present study, but these represent efficiencies appropriate to the principal goal of the study — gauging the relative values of these sensors.

Compact CubeSat Gamma-ray detector for GRID mission

Gamma-Ray Integrated Detectors(GRID)mis-sion is a student project designed to use multiple gamma-ray detectors carried by nanosatellites(CubeSats),forming a full-time all-sky gamma-ray detection network that monitors the transient gamma-ray sky in the multi-mes-senger astronomy era.A compact CubeSat gamma-ray detector,including its hardware and firmware,was designed and implemented for the mission.The detector employs four Gd 2 Al 2 Ga 3 O 12:Ce(GAGG:Ce)scintillators coupled with four silicon photomultiplier(SiPM)arrays to achieve a high gamma-ray detection efficiency between 10 keV and 2 MeV with low power and small dimensions.The first detector designed by the undergraduate student team onboard a commercial CubeSat was launched into a Sun-synchronous orbit on October 29,2018.The detector was in a normal observation state and accumulated data for approximately one month after on-orbit functional and performance tests,which were conducted in 2019.

An Orbit Determination Using SGP4 Propagator and Doppler Shifts for CubeSats

The two line elements(TLEs),released by the North American Aerospace Defense Command(NORAD),are chosen for CubeSats' mission operators.Unfortunately,they have errors and other accompanied problems,which cause large deviations in the in-track component.When a TLE value is available at a certain epoch,the dominant error is the angular error.It is proposed to correct the angular error by solving-for the mean argument of latitude at the desired epoch.A batch least squares technique and range rate measurements are used for the correction process.With the assistance of satellite tool kit(STK)software and Matlab,a simulation to verify the orbit determination(OD)technique is implemented.This paper provides an angular correction low cost OD method and presents a complete analysis for various test cases.This approach maintains high accuracy in cross-track and radial and makes great improvement in in-track at the same time,but it is exclusive for circular orbits.When it is applied to an elliptical orbit,the error will be unacceptable.Therefore,the angular error is corrected using the longitude of periapsis which totally mitigates the error at the epoch under consideration.For inclinations less than 20 o,the mean longitude is preferred for the angular correction as it provides more accuracy compared with the mean argument of latitude.

CubeSat通信子系统综述

CubeSat是由加州理工学院和斯坦福大学提出的一种纳卫星标准。CubeSat具有体积小、发展周期短、成本低等特点,近几年得到飞速发展。本文针对目前的CubeSat通信系统进行了系统性的综述与总结,并简要介绍了通信子系统的框架。最后结合人们对通信速率、通讯时间的需求分析,给出了未来的发展方向以及如今的研究状况。

Low Profile UHF Antenna Design for Low Earth-Observation CubeSats

This paper reveals a new design of UHF CubeSat antenna based on a modified Planar Inverted F Antenna(PIFA)for CubeSat communication.The design utilizes a CubeSat face as the ground plane.There is a gap of 5 mm beneath the radiating element that facilitates the design providing with space for solar panels.The prototype is fabricated using Aluminum metal sheet and measured.The antenna achieved resonance at 419 MHz.Response of the antenna has been investigated after placing a solar panel.Lossy properties of solar panels made the resonance shift about 20 MHz.This design addresses the frequency shifting issue after placing the antenna with the CubeSat body.This phenomenon has been analyzed considering a typical 1U and 2U CubeSat body with the antenna.The antenna achieved a positive realized gain of 0.7 dB and approximately 78%of efficiency at the resonant frequency with providing 85%of open space for solar irradiance onto the solar panel.

Advanced Space Laser Communication Technology on CubeSats

The free space optical communication plays an important role in space-terrestrial integrated network due to its advantages including great improvement of data rate performance,low cost,security enhancement when compared with conventional radio frequency(RF) technology.Meanwhile,CubeSats become popular in low earth orbit(LEO) network because of the low cost,fast response and the possibility of constituting constellations and formations to execute missions that a single large satellite cannot do.However,it is a difficult task to build an optical communication link between the CubeSats.In this paper,the cuttingedge laser technology progress on the CubeSats is reviewed.The characters of laser link on the CubeSat and the key techniques in the laser communication terminal(LCT) design are demonstrated.

CubeSat结构热控案

CubeSat以体积小、成本低、研制周期短等优点受到越来越广泛的关注,但CubeSat的高度集成化、模块化设计对结构热控提出了更高的要求,而且宇宙中的辐射也会对立方体卫星造成影响。本文在参考国外高校对CubeSat的结构热控和辐射防护方案基础上,对结构热控与辐射防护方案进行分析与讨论,给出更理想的方案。

CubeSat Autonomous Orbit Determination Based on Magnetometer and Sun Sensor Data

CubeSats have evolved from purely educational tools to a standard platform for technology demonstration,scientific instrumentation and application in less than a decade.They open the door to new challenges and interplanetary missions which lead to the direct realization of autonomous orbit determination(AOD)which has been investigated before with different integrated sensors combined with various filters.Mostly these studies were carried out for larger satellites with more accurate sensors.Magnetometer and sun sensor combined with extended Kalman filter(EKF)are chosen to complete AOD task considering their light weight.For the purpose of AOD and the computational cost requirements imposed on CubeSats,it is important to develop and apply low cost on-board models.In this perspective,a magnetic model based on a table look up is proposed to generate the reference magnetic field with a low computational burden.In current article the simulations through Matlab and Satellites Tool Kit(STK)especially focus on the accuracy of the AOD system provided by this model.For analysis three EKFs are carried out with different calculation models and data types.The system based on the proposed model is fully autonomous,low-cost and has moderate-accuracy required by most CubeSats missions.The AOD system can be applied as main or backup system depending on the space missions′demands.

Science Missions Using CubeSats

As the role of missions and experiments carried out in outer space becomes more and more essential in our understanding of many earthly problems,such as resource management,environmental problems,and disaster management,as well as space science questions,thanks to their lower cost and faster development process CubeSats can benefit humanity and therefore,young scientists and engineers have been motivated to research and develop new CubeSat missions.Not very long after their inception,CubeSats have evolved to become accepted platforms for scientific and commercial applications.The last couple of years showed that they are a feasible tool for conducting scientific experiments,not only in the Earth orbit but also in the interplanetary space.For many countries,a CubeSat mission could prompt the community and young teams around the world to build the national capacity to launch and operate national space missions.This paper presents an overview of the key scientific and engineering gateways opened up to the younger scientific community by the advent and adaptation of new technology into CubeSat missions.The role of cooperation and the opportunities for capacity-building and education are also explored.Thus,the present article also aims to provide useful recommendations to scientists,early-career researchers,engineers,students,and anyone who intends to explore the potential and opportunities offered by CubeSats and CubeSats-based missions.

利用CubeSat自由漂移群提高南极通信网络覆盖

我国目前在南极已建有四座科考站,由于地势偏远,环境恶劣,南极地区的通信基础设施薄弱。本文讨论利用Cube Sat自由漂移群来提高南极通信网络覆盖,利用STK软件对Cube Sat星群进行仿真发现,构建规模为10颗的Cube Sat星群即可对四座科考站进行较好的覆盖,为南极通信网络建设提供一种可靠的选择。

Qualification and validation test methodology of the open-source CubeSat FloripaSat-I

The FloripaSat-I project consists of an initiative from the Federal University of Santa Catarina(UFSC),in Brazil,to train students to design,test and integrate innovative space systems.The group just developed its first open-source CubeSat,the FloripaSat-I,which aims to empower students to develop space systems through a practical approach,where they have full control of the design and test of a real spacecraft.The project has already gone through all the stages of a CubeSat mission prior to the launching and operation stages.A prototype of the satellite,as well the engineering models 1 and 2(EM-I and EM-II)were built.The expertise provided by the engineering models allows the development of a functional flight model(FM).This paper presents the validation and qualification tests that pass various FloripaSat-I models,from the engineering model to the flight model.All stages of the project are described,the tests performed in each phase,as well as the lessons learned.Thus,this paper serves as a guidance for other university teams that want to test their own CubeSats,as well as teams that want to use the open-source hardware and software left as heritage by this project.

CubeSat系统结构与应用研究

文章对CubeSat的系统结构及应用现状做了综合性的介绍和讨论。CubeSat具有成本低、体积小、重量轻、入轨快、研制周期短、功能扩展性强等优点,是近几年来航天器领域的研究热点,发展迅速。文章对CubeSat的星务计算系统、姿态控制系统、电源系统、热控系统和通信系统进行了有体系的归纳总结。结合现阶段CubeSat在观测任务、分布式空间组网、新技术演示验证等方面的应用,给出了对于CubeSat未来发展方向的讨论。

CubeSat太阳电池阵研究进展

立方体卫星属于微小卫星,其具有成本低、周期短等特点,因此得受到广泛应用。主要针对立方体卫星太阳能电池阵,分别从太阳电池、太阳电池基板、锁紧分离机构、太阳电池阵展开机构4个不同组成部分研究进展进行阐述,并对立方体太阳电池阵技术的发展趋势进行展望。

一种立方星模块化电源系统的设计与在轨试验

立方星实用化发展对其电源系统提出了更高的要求,传统立方星电源的功率容量和扩展能力已难以满足遥感、通信等立方星应用的需求。该文针对此问题提出一种模块化电源系统的设计与研制方法:系统对外采用统一的结构、信息和功率接口,实现与卫星平台的松耦合;内部设计多种标准化的模块单元,通过模块数量的配置和堆叠结构,实现功率容量和配电通道灵活扩充,从而快速满足多样化任务立方星的供电需求。以中国青少年科普卫星八一03星为例,开展电源系统设计方法的验证与工程实现,研制周期缩短至两个月。在轨试验表明,所设计的模块化电源系统工作稳定可靠,能够适应百瓦量级以内不同载荷任务立方星的功率需求。

青藏高原河流网络高分CubeSat遥感监测

河流网络是地表水循环的重要组成部分,如何实现河流网络动态监测已成为河流遥感研究的热点。近年来,以PlanetScope为代表的CubeSat小卫星已具备了米级空间分辨率、1 d重访周期的优势,这为河流网络高时空分辨率动态监测提供了可能。本文以青藏高原长江源区的通天河流域(227 km^(2))为研究区,选取2017-05—2017-105期3 m空间分辨率CubeSat遥感影像,增强河流横纵剖面特征自动化提取了河流网络,研究了通天河流域河流网络动态变化,对比分析了3 m CubeSat与30 m Landsat 8、10 m Sentinel-2所提取的河流网络,以及5种现有水体数据集(GRWL,GSW,FROM-GLC 2017,OpenStreetMap,HydroSHEDS)。研究结果表明:(1)研究区内河流网络5月水系密度较低(0.38 km^(-1)),7—8月河流网络进入丰水期,水系密度显著增加至0.61 km^(-1),9月河流网络进入平水期,水系密度趋于平稳(0.53 km^(-1)),随后迅速退化并于10月开始冻结,水系密度迅速降低至0.37 km^(-1);(2)采用高空间分辨率CubeSat所提取的河流网络能够识别更多细小河流(河宽3—30 m),CubeSat所提取的河流总长分别为Landsat 8、Sentinel-2所提取河流总长的1.6倍和1.3倍;(3)CubeSat所提取的河流网络水系密度高于现有水体数据集(2.9—12.4倍),弥补了现有水体数据集无法反映细小河流的不足。

一种模块组装6U立方星的总体设计与在轨验证方法

从立方星实用化角度出发,提出了一种模块组装6U立方星的总体设计方法。首先,通过立方星结构布局的优化设计,将立方星平台部分和载荷部分分别布局于6U立方星的左右侧,实现了卫星平台和有效载荷的松耦合设计。其次,针对立方星星上和地面站资源有限的约束,提出了利用UHF/VHF+X频段的测控数传一体化方法,实现了立方星测控数传的模块化设计,解决了能源和体积约束条件下立方星大容量数据传输难题。再次,针对6U立方星模块组装的要求,分别提出了电源分系统、姿控分系统、离轨帆分系统的模块化设计方法。最后,以中国青少年科普卫星BY-03星为例,将紫外相机、计算光谱相机通过标准化接口设计,从而实现了卫星平台与载荷的模块化快速组装与集成测试。在轨试验结果验证了所提出的模块组装6U立方星设计方法能够适应多种有效载荷任务需求,并满足立方星快速研制与测试的需求。

Electronics system for the cosmic X-ray polarization detector

This study presents an electronics system for cosmic X-ray polarization detection(CXPD).The CXPD was designed as a high-sensitivity soft X-ray polarimeter with a measurement energy range of 2-10 keV carried by a CubeSat.A stable and functionally complete electronics system under power and space constraints is a key challenge.The complete CXPD electronics system(CXPDES)comprises hardware and firmware.CXPDES adopts a three-layer electronic board structure based on functionality and available space.Two gas pixel detectors(GPDs)were placed on the top layer board,and CXPDES provided the GPDs with voltages up to-4000 V.Each GPD signal was digitized,compressed,encoded,and stored before being transmitted to the ground.The CXPDES provided stable and high-speed communication based on a scheme that separated command and data transmission,and it supports the CXPDES in-orbit upgrade.In addition,environmental monitors,silicon photomultiplier(SiPM)triggers,power management,GPDs configuration,and mode switches were included in the overall operating logic of the CXPDES.The results obtained by testing the CXPDES showed that it satisfied all the requirements of CXPD.The CXPDES provides design experience and technological readiness for future large-area X-ray polarimetry missions.

立方星SMA直线作动解锁机构的优化设计

为实现在空间、功耗严苛约束下立方星太阳板的可靠解锁,研制了一种形状记忆合金(SMA)丝直线作动解锁机构。采用弹簧-SMA结构,依靠弹簧力锁紧,通过SMA丝加热产生回复应力驱动拔销运动实现解锁。建立了机构的数学模型,并通过仿真得到SMA解锁机构的行程、解锁时间、功率与合金丝直径、工作电压的描述关系。以解锁时间和功率的整体评价最优为目标,采用粒子群优化算法对合金丝的直径和工作电压进行优化设计,得到直径0.5 mm的SMA解锁机构在1.2 V驱动电压下具有最佳工作特性。最后对优化结果开展实验分析,表明作动机构的解锁时间为3.2 s,功率为3.55 W,拔销行程为1.8 mm,与仿真一致。所研制的解锁机构可靠性高,工作特性一致,具有较好的适应性,已通过各项环境实验并成功在轨应用。

立方星阻力帆气动特性的DSMC模拟

立方星的大量发射将加剧近地轨道的空间碎片问题。阻力帆技术利用气动阻力,可使得卫星被动离轨并进入大气层烧毁。离轨周期的计算需要对稀薄气动特性做出精确预测。本文采用NNW-DSMC软件,对立方星阻力帆离轨装置在不同高度下的稀薄绕流流场进行数值模拟,分析了气动特性的变化规律。结果表明,NNW-DSMC的计算结果与文献结果吻合良好(阻力系数与参考结果的相对误差小于1%,最大热流的相对误差在6%以内),进一步验证了其计算精度和可靠性。将碰撞松弛数设置为温度的函数后,转动和振动温度降低,平动温度升高,流场总温度也增加了约10%。为增加模拟的保真度,应将松弛碰撞数设置为温度的函数。本文结果可为后续的立方星离轨动力学分析提供支撑。