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.

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.

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.

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.

Attitude Regulation With Bounded Control in the Presence of Large Disturbances With Bounded Moving Average

The attitude regulation problem with bounded control for a class of satellites in the presence of large disturbances,with bounded moving average,is solved using a Lyapunov-like design.The analysis and design approaches are introduced in the case in which the underlying system is an integrator and are then applied to the satellite attitude regulation problem.The performance of the resulting closed-loop systems are studied in detail and it is shown that trajectories are ultimately bounded despite the effect of the persistent disturbance.Simulation results on a model of a small satellite subject to large,but bounded in moving average,disturbances are presented.

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.

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.

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。

A Pathway to Small Satellite Market Growth

The United States is experiencing a renaissance in interest in space due to the advent of new lowercost small spacecraft. New launch entrants, such as Interorbital Systems, promise to lower launch cost levels. Many developers also benefit from free-to-developer launch services from NASA or the ESA. Unfortunately, existing commercial off the shelf (COTS) CubeSat hardware is priced based on amortization of design costs across low-sales volume. A lack of trained staff in any one of the numerous disciplines required for spacecraft design or other resources required for in-house development restricts entry into the small satellite industry to those who can afford expensive COTS hardware or pay for significant design expenses. With entry-level satellite hardware still priced in the six-figure range, limited market growth is expected even as the average CubeSat launch cost continues to decline. A new archetype could lower barriers to entry for building small satellites. A free, public-domain architecture for building a small satellite could allow low-cost, in-house satellite development. Under this paradigm, the expenses for initiating a small satellite program are limited to component and launch vehicle costs. The proposed framework allows for broad access to small satellite hardware, greatly increasing the size of the small satellite developer community. In the context of the small satellite market, freely offering plans to construct an entry-level satellite will court new non-traditional actors into building space hardware for launch on commercial and government small satellite launchers. The low-cost, high flight rate possible with the next generation of launch systems affords operators the freedom to experiment and innovate in a risktolerant environment. Successfully demonstrating products and services utilizing low-risk, publicdomain plans will stimulate demand for mature and more capable flight systems in the retail marketplace. If technical schools, community colleges, universities, small businesses and even amateurs can enter into the small satellite ecosystem, at an affordable entrance price, a positive spiral of increasing demand and decreasing cost may be created over time. A free, public domain satellite architecture may, thus, open the door to sustained growth and commercial opportunity for the small satellite industry.

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。

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。

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.

Risk Analysis Comparison between the Mission NANOSATC-BR1 and NANOSATC-BR2

The goal of this work is to perform the risks analysis of the mission NANOSATC-BR1 and NANOSATC-BR2 and then compare them linearly. The NANOSATC-BR1 and NANOSATC-BR2 are the first and the second satellite, respectively. They belonged to the project NANOSATC-BR-development of CubeSats, which is performed in the facilities built by the partnership between the National Institute of Space Research and the Technological Center from Federal University of Santa Maria. The project focuses on the development of a scientific instrumentation and, simultaneously, the design development, construction, qualification and launch of a national scientific nanosatellite, in a cube shape with 100 mm of edge and near to 1.33 kg of mass, per unit （U）. The risk analysis was held to identify and minimize the project＇s risks of failure, due to its complexity, assuring the mission success, preventing extra pays and rework. The software, CubeSat Mission Design Software Tool for Risk Estimating, which uses statistical regression methods, was used. So, we were capable to measure the project＇s most critical steps assuring its success. The NANOSATC-BR1 was launched in June 19 and it is orbiting the Earth in a nominal regime and the NANOSATC-BR2 has been scheduled to be launched in 2016.

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。

An atmosphere-breathing propulsion system using inductively coupled plasma source

CubeSats have attracted more research interest recently due to their lower cost and shorter production time.A promising technology for CubeSat application is atmosphere-breathing electric propulsion,which can capture the atmospheric particles as propulsion propellant to maintain longterm mission at very low Earth orbit.This paper designs an atmosphere-breathing electric propulsion system for a 3 U CubeSat,which consists of an intake device and an electric thruster based on the inductively coupled plasma.The capture performance of intake device is optimized considering both particles capture efficiency and compression ratio.The plasma source is also analyzed by experiment and simulation.Then,the thrust performance is also estimated when taking into account the intake performance.The results show that it is feasible to use atmosphere-breathing electric propulsion technology for CubeSats to compensate for aerodynamic drag at lower Earth orbit.

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。

A brief review of alternative propellants and requirements for pulsed plasma thrusters in micropropulsion applications

Technological miniaturization has enabled the development of small satellites weighing as little as 1 kg.Unfortunately,there is still a lack of suitable efficient micropropulsion systems at these scales.The pulsed plasma thruster is a structurally simple form of electric propulsion.This simplicity also makes it ideally suited for miniaturization.Its history can be traced back to applications in satellites that are much larger than micro/nano-satellites.The vast majority of modern pulsed plasma thrusters use solid polytetrafluoroethylene(PTFE)as a propellant.Unfortunately,at lower discharge energy levels such as those necessitated by the power limitations of micro/nano-satellites,PTFE has a tendency to exhibit carbon deposition,which can ultimately lead to thruster failure.In this new era of small satellites,it is important to consider alternative propellants in the miniaturization of pulsed plasma thrusters.This brief review discusses the needs and limitations of small satellites and alternative propellants that may be able to meet these needs.Such propellants may be able to offer advantages such as a longer thruster lifetime,a higher specific impulse,or a higher thrust-topower ratio.This would enable the development of different types of pulsed plasma thrusters that can be tailored towards specific mission requirements.