Cubesat

This paper gives an overview of CNES activities in the field of very High Data Rate Telemetry (HDRT) for new very high resolution Earth observation satellites.

A CNES technological program 'OTOS' (former 'CXCI') was committed in 2011 to develop and demonstrate key technologies for a new generation of optical observation satellites system ('Pléiades' follow-on system), among them in particular an active telescope demonstrator.

A part of the program was allocated to HDRT developments:

- a 'DVB-S2 transmitter' and a 'DVB-S2 receiver' using CCSDS recommended standard 131.3 [1] (calling ETSI DVB-2 standard [2])

- an Antenna Pointing System (APS) based on an Antenna Pointing Mechanism (APM).

This paper presents the processes of developing a physical solution to the structural subsystem of the Brazilian Technological Institute of Aeronautics – ITA CubeSat, the AESP-14 Project. This work also shows static and modal structural analysis through computational methods, in order to predict the structural response to launch environment. The INPE’s capacities for manufacturing CubeSat main structures, are also discussed and proved through Reverse Engineering applied to a Commercial Off The Shelf - COTS structure. Results of analysis showed that in average launch environment levels, the structure developed reaches maximum stresses quite below used material’s limits. Natural frequencies found are also eligible to major piggy-back launch requirements.

During the mission design for the first Ecuadorian satellite, the NEE-01 PEGASUS, the need arose for having a robust power supply in order to charge our already large battery banks; Calculations showed that we will need no less than 40 of our solar cells. The engineering team of the Ecuadorian Civilian Space Agency began studying the design and development of a very thin, deployable, multipanel solar arrays, able to fold in no more than 6 millimeters height as our spacecraft was an 1U cubesat design and the P-POD restrictions allowed a maximum clearance of 6.5 millimeters. Once in orbit each array will deploy to 3 panels each, measuring 27 centimeters by 8 centimeters wide with a total of 57 solar cells for a maximum of 14.25 watts of power generation capability. The main challenge was to simplify the release and deployment mechanism in order to meet the 6 millimeter restriction in folded configuration, the solution was the use of a titanium scaffold coupled with memory shape alloys and the modulation of the tensile strength of space-grade polymers by creating geometries that will naturally provide the deployment force needed and the use of the sun's heat to activate the memory shape alloy component's transition that will provide the reminder of the deployment force needed to acquire final deployment geometry. The result was a device that uses no compound hinges for release and deploy that not only met the mission requirements but actually surpassed them; After much testing and trials they were own and successfully operated in NEE-01 PEGASUS and NEE-02 KRYSAOR, after more than 3 years in space, the arrays keep providing enough power to run the payload at full capacity. A new version of this array will flight in two upcoming U.S. cubesat mission in 2017 and 2018 and the upcoming twelve missions of this program. This paper will describe the development and testing of this array in the PEGASUS missions as well as the upgraded design for the new mission in 2017.

The aim of this report is to design and implement in Simulink the attitude determination and control system of a 6U CubeSat orbiting around the Earth in LEO environment and subjected to orbital perturbations of magnetic field, SRP, gravity gradient and atmospheric drag.
The mission is to detumble it and then point it towards the Sun.

This paper presents the system's architecture, the description of the adopted model, the
analysis of the control algorithms used and all the results obtained.

Swiss Federal Universities of Lausanne and Zurich have initiated a new 1U Cu- beSat project. The main objective of the CubETH is to demonstrate use of com- mercial GNSS receivers in space and test Precision Orbit Determination algo- rithms. One of the key driving requirements is to provide zenith pointing with a 20 degrees of precision and rotation rate less than 2 degree / second, in order to track GNSS constellation satellites. This paper will describe details of Attitude Determination and Control Subsystem (ADCS) based on magnetotorquers in or- der to satisfy the science requirements. We will discuss lessons learned from the ADCS implementation on the first Swiss nanosatellite SwissCube (in operation since 2009) and we present the flat shaped magnetotorquers (MTQs) designed in the laboratories of the Ecole Polytechinque Federale de Lausanne (EPFL) in Switzerland, detailing design, the test setup and t procedures performed.
We present theoretical calculations for the magnetotorquer parameters, simula- tions, details of manufacturing and results of testing done in the shielded room of the Ecole Poly-techinque Federale de Lausanne. Testing shows a 93% of match be-tween the 3D model and tests done with the magnetic probe on the new de-sign prepared for CubETH, where the design slightly changed from the previous shape of SwissCube.
The paper presents the description of the manufacturing and the process fol- lowed in order to highlight the encountered issues on the magnetotorquers fabri- cation. We address the process to select the proper materials and quantities for the manufacturing of flight and engineering models, ad-dressing the required characteristics for the material selected.

BeEagleSat uydusu ülkemizde üniversiteler, büyük sanayi ve KOBİ işbirliğinde, Avrupa Birliği QB50 projesi kapsamında geliştirilmekte olan iki birim bir küp uydudur. QB50 projesi ile ilk defa küp uydular birincil yük olarak uzaya erişim olanağı bulacaktır. Ayrıca, çok uluslu ve çok kurumlu bir yapılanma içerisinde uzay sistem geliştirme tecrübesi bulunan birçok büyük uzay kurumunun deneyiminin de kullanarak küp uydular kümesi geliştirme birikimi oluşturulmaktadır. Uyduların ana amacı henüz yeterince incelenmemiş termosfer tabakasında proje kapsamında geliştirilmekte olan duyargalar ile ortam ölçümleri yapılması, yapılan ölçümlerin dünya çapındaki yer istasyonları tarafından toplanması ve bilginin paylaşılmasıdır. Ölçülen veriler ile daha doğru termosfer modellemesi yapılması öngörülmektedir. BeEagleSat uydusu ortakları da QB50 projesinin uluslararası ortamı içerisinde dünya deneyimlerini kendi tecrübeleri ile birleştirmektedir. Uydunun yönelim kontrol ve duyarga sistemleri proje kapsamında QB50 konsorsiyumu tarafından sağlanmakta, ikinci ana yük ve diğer alt sistemler ise proje ekibi tarafından geliştirilmektedir.

For most satellite missions, it is essential to decrease the satellite angular velocity. The Β algorithm is a common algorithm to stabilize the spacecraft by using magnetorquers. Controlling the satellite using the magnetorquers is part of the attitude control subsystem detumbling mode. Due to the oscillating disturbances in the space environment, the required initial conditions needs analysis. As a consequence, the satellite stays in Β detumbling mode for the entire operation. In detumbling mode, the spacecraft oscillates around its spatial axes. The purpose of this paper is to extend the Β algorithm with a disturbances compensation module and to achieve a reduction of satellite's angular velocity. The developed algorithm could reduce satellite's angular velocity up to 10-11 degree. 1. Introduction The success of a space mission depends on sophisticated attitude control subsystem (ACS). As the ACS can only be activated if the spinning about the satellite's own axes remains within certain boundaries, uncontrolled oscillation should be minimized, even if a precisely determined orientation is not required for the particular mission. Due to the increasing importance of small and very small satellites such as CubeSat satellites, which are mainly operating in a low earth orbit (LEO) under a relatively strong earth magnetic field, the relevance of magnetic attitude control systems has also grown [1, 2]. This is pushed by magnetorquers' low prices, their space saving assembly, and the independence of propellant. Therefore, they are often the only actuators in CubeSat missions. They are integrated inside the solar panels to obtain the necessary electrical power [3]. The Β law, a purely magnetic control scheme, was originally proposed in [4]. Since then, this control law has been adopted as the primary detumbling solution in small satellites such as Pico Satellite Solar Cell Testbed-2 (PSSCT 2) [5] and T-SAT1 [6]. While the aforementioned studies present satisfactory detumbling performances, the initial conditions are difficult to estimate in real applications. The tuning factor, for instance, is generally chosen based on trial and error experiments. However, the initial factor chosen may not reject the oscillating disturbances effectively, and the control law may fail in case the disturbances change. Therefore, the satellite is not detumbled effectively. The aim of this work is to present a novel yet convenient Β algorithm to subside the effect of oscillating disturbances in the space environment. The study presents a solution to control the current by a pulse width modulation (PWM) signal and proposes a gain factor function to obtain the optimum torque to reject the disturbance. The method has been simulated and tested further on a CubeSat to validate the feasibility of the proposed scheme. The paper is organized as follows: the conventional and the novel Β algorithms are introduced followed by the description of the mission and the strategy. The validation procedure using the CubeSat and the obtained results are presented later followed by the simulation results. The conclusion describes the findings of the study.

This review research examined technical papers covering engineering topics related to small satellites. Papers were selected based on the use case or concept of the spacecraft they pertained to. Papers reviewed focused on niche use cases or concepts, defined for the purposes of this research as those use cases or concepts where no spacecraft filling that use case has ever been launched. From these niches, this review research examined the technical aspects of the use cases which have been explored and become understood, and isolated those which had not, especially those indicated in research papers as areas needing development in order to realize a functioning spacecraft. This review focused particularly on trade studies, mission planning analyses, and analyses of obvious required hardware for mission realization. Several major unsolved engineering problems associated with niche use cases were found, and the specifics of their engineering problems were enumerated where possible.

The NTNU Test Satellite (NUTS-1) is an educational CubeSat project aiming to launch a student designed and manufactured satellite. The project is one of three participants in the Nor-wegian CubeSat program ANSAT. The current primary goal is to have an engineering model ready by August of 2016. Communication with the ground segment will be in the VHF and UHF bands, allowing for full duplex transmission. The ground segment will be based upon a Software Defined Radio (SDR) to enable an easier and more flexible configuration. The SDR-platform used is the Ettus Research USRP, supported by a GNU Radio implementation on a computer. The link layer packet protocol implemented in the prototype is NGHam, a link protocol partly inspired by AX.25. In order to improve the link reliability, it features Reed Solomon codes for Forward Error Correction (FEC). This makes the data transmission more robust compared to i.e. AX.25, which does not implement FEC on the link layer directly. The required GNU Radio modules have been designed and implemented. An end-to-end communication between the USRP and the NUTS VHF module has been proved. A ground station based on traditional HAM radio equipment requires several bits of hardware, such as a radio, TNC or third part modems in order to enable packet transmission. By replacing this with a SDR setup the ground station will be more flexible; it will be easier to receive data from different satellites that might be using different link protocols and message formats. Utilising open source software, such as GNU Radio, gives radio amateurs around the world the opportunity to receive data from NUTS using cheap SDR hardware such as the RTLSDR USB dongles. Finally, as an SDR system can support a wide range of frequency bands, it will be easy for other project groups to implement support for their satellite mission using such an SDR based system. Support for other link protocols can easily be implemented. Messages received from the satellite(s) can easily be made available online.

Emerging technologies of CubeSat communication and navigation systems enable new approaches such as larger bandwidths, spectrum and security decrement and high speed communications. In order to create a vantage point, young professionals and students from the four corners of the earth had performed a comprehensive study at the 2014 Space Generation Congress in Toronto, Canada under "CubeSat Swarms Communication Networks and Policy Challenges" working group. While potential possibilities are endless for the structure of Cubesat networks, decisions made amongst the group were based on existing technologies and guidelines. Therefore, the working group discussed (1) short and long term technical challenges (2) policy requirements, (3) radio communication bandwidth limitations, (4) data collection and transmission regulations and (5) the standardization of the CubeSat communication system. Technical challenges for small satellite missions involve limitations of link budgets, the size of the deployable high gain antennas, optical and laser communication and the restriction of the link budget due to the interferences. In addition, policy issues have immaturities for frequency allocation and registration complimenting the short lifespan of CubeSats. The standardization of mission operations enables a space communication network architecture that of which is similar to the internet, incorporated into CubeSat Swarms. The group suggests a CubeSat network system architecture including inter-swarm and intra-swarm constellations, optical and laser communications and delay-tolerant networks (DTN). The proposed CubeSat communication network also consists of inter-swarm constellation communications along with intra-swarm constellations sustained through four different basic data links, a mother-daughter satellite framework, and net-neutrality throughout the network. In the meantime, policy regulation recommendations allow global communication by reducing data downlink time. Governments, as well as service providers, treat all data used online the same regardless of its origins, platform, and users. The standardization of the CubeSat network system was formed by operator expectations for high downlink speeds, equal priority for data transfers, and streamlined registrations. The simplified registration process for CubeSat-Swarms is more efficient by establishing new baseline legal framework, rules, and standards. This would help all users and operators in this sector, including entrepreneurs, licensing bodies, and end-users. Saving time for everyone while achieving maximum efficiency, utilization of the time and results are the end result of proposed system architecture by the working group.

DVB-S2 is a CCSDS telemetry standard, called adaptation standard in the CCSDS terminology, fully reusing the ETSI DVB-S2 mass-market telecommunication standard, thus providing the advantage of a wide diversity of very robust commercial mass market receivers, cheaper than the receivers dedicated to space telemetry links. CNES is currently upgrading with Syrlinks an existing X Band Transmitter for cube & nanosatellites (TRL 9) to use DVB-S2 CCSDS telemetry standard. The Variable Coding and Modulation (VCM) mode will provide up to 60% increase of the downloaded data compared to Constant Coding and Modulation (CCM), a link budget improvement of about 2 dB in QPSK for the same transmitted power and a better spectral efficiency.