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Increased Flexibility and Reliability for CubeSats through Distributed Telemetry and Control
Abstract
At the Laboratory for Rapid Space Missions, we develop CubeSat missions and ISS-based experiments with diverging requirements. Due to limited manpower and resources, we cannot develop new and specifically tailored software and hardware for each of these projects. Instead, we propose the use of a distributed approach with well-defined and statically checked components that can be reconfigured and reused for several missions. The DOSIS framework developed at the Technical University of Munich provides the features required for such a setup. We present the conceptual design of the framework and briefly introduce the first missions using the DOSIS hardware and software setup.
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This article reports the ongoing work on an environment for hardware-in-the-loop (HIL) and software-in-the-loop (SIL) tests of CubeSats and the benefits gained from using such an environment for low-cost satellite development. The satellite tested for these reported efforts was the MOVE-II CubeSat, developed at the Technical University of Munich since April 2015. The HIL environment has supported the development and verification of MOVE-II’s flight software and continues to aid the MOVE-II mission after its launch on 3 December 2018. The HIL environment allows the satellite to interact with a simulated space environment in real-time during on-ground tests. Simulated models are used to replace the satellite’s sensors and actuators, providing the interaction between the satellite and the HIL simulation. This approach allows for high hardware coverage and requires relatively low development effort and equipment cost compared to other simulation approaches. One key distinction from other simulation environments is the inclusion of the electrical domain of the satellite, which enables accurate power budget verification. The presented results include the verification of MOVE-II’s attitude determination and control algorithms, the verification of the power budget, and the training of the operator team with realistic simulated failures prior to launch. This report additionally presents how the simulation environment was used to analyze issues detected after launch and to verify the performance of new software developed to address the in-flight anomalies prior to software deployment.
MOVE-II (Munich Orbital Verification Experiment) is the second satellite of the Technical University of Munich's educational CubeSat program. On December 3, 2018, the satellite was launched on the SSO-A SmallSat Express from the Vandenberg Air Force Base. The following paper shows on-orbit results of the first eight months of operations. It includes analyses based on our own data as well as the open-source ground station network SatNOGS. Lessons learned from mission operations and recommendations for future educational missions are provided. The technical goals of the mission are verifying the satellite's bus and the qualification of a novel type of quadro-junction solar cells. Over 200 students have been developing and testing all components of the satellite since the beginning of the project in April 2015. During the course of the project, the students designed all necessary technology for a CubeSat bus, with the exception of the electrical power system and the on-board computer's hardware. Furthermore, the students developed ground station software as well as an operations interface from scratch. The technological achievements of the mission range from a linux-based onboard computer software over a magnetorquer-based attitude determination and control system to two novel transceivers for UHF/VHF and S-Band. A reusable mechanism, based on shape-memory-alloys, deployed the four solar panels, providing the necessary power. Only hours after the deployment, we received the first signals of the satellite. The commissioning of the ground station and the effects of an insufficient power budget of the tumbling satellite preoccupied us during the first month, as well as frequent watchdog resets. During the commissioning of the Attitude Determination and Control System (ADCS), a spin rate of 200 °/s was observed, although the actuators were not activated yet. Detailed analysis with the help of recordings provided by our own ground station as well as the SatNOGS ground station network revealed a slow increase of the spin rate since the launch. In the following weeks the spin rate further increased to over 500 °/s. Afterwards we were able to modify our ADCS actuation in a way to reduce the spin rate again. Currently MOVE-II is detumbled and we are moving towards regular scientific operation. After a presentation of the results, lessons learned from our mission operations are discussed. The paper discusses the measured values and analyzes the reasons for the observed behaviour. Also the changes made on MOVE-IIb, a slightly improved copy of MOVE-II, will be explained. The paper concludes with recommendations for designers of upcoming educational satellite missions, especially regarding resilience against negative power budgets.
The recent miniaturization of space components and electronics has allowed the design of smaller satellites which are considerably cheaper to build and launch than conventional satellites. This decrease in the total cost of a space mission has boosted a new growing market for small satellites and, as the number of small satellites keeps increasing, there is a raising demand for reusable software across nanosatellites. The NanoSat MO Framework provides a standard on-board software framework for nanosatellites based on the CCSDS MO framework, that facilitates not only the monitoring and control of the nanosatellite software applications, but also the interaction with the platform peripherals. This is achieved by using the CCSDS Mission Operations Monitor and Control services included in the MO service suite and by defining a set of new Platform services which shall also follow the MO services framework architecture. The paper describes the NanoSat MO Framework, the associated set of high-level components and possible end-to-end deployment scenarios including the reference implementation in ESA’s OPS-SAT mission. Moreover, defines an app in the context of the NanoSat MO Framework, as well as, how they can become portable software entities and be distributed among different platforms. The framework opens up many possibilities for future work and extensions due to its modular and flexible design approach which is not limited to the space segment but extends down to ground by providing all the building blocks for a complete and free end-to-end solution.
This paper presents the on-orbit results and the lessons learned from First-MOVE (Munich Orbital Verification Experiment), the first CubeSat mission of the Institute of Astronautics (LRT) at the Technische Universität München (TUM). The development of the satellite started as a student project in 2006. First-MOVE was launched on November 21st 2013. The student-designed and built satellite was operated for almost a month. On December 19th 2013 a major malfunction occurred, presumably due to an anomaly in the on-board data handling system (OBDH), which left the satellite in a mode where it is only transmitting continuous wave (CW) beacons. Although the short mission duration prevented several mission objectives from being achieved, the overall program can be considered a success, as it permitted more than 70 students hands-on experience and led to major in-house technology and spaceflight processing developments. The main aspects of a university-led satellite development, the results of the mission and both technical as well as educational lessons learned are described, including the management and planning of student projects as well as motivational and system engineering aspects. These aspects include planning the project around student's schedules rather than in a traditional, linear fashion, the careful selection and distribution of team members to subsystem teams and the deviation from traditional systems engineering process flows in order to retain student motivation. The importance of large milestone reviews and kick-off events as short term goals and as a means to recruit new team members are highlighted. Academic outreach programs included a one week summer school held in 2011 to recruit and train new students in a time-efficient setting in relevant technical aspects. The paper explains in more detail the technical lessons learned from the major satellite subsystems, both self-developed and purchased. The self-developed systems include, among others, the design of the solar-panel release mechanism, the unique CMOS latch-up protection system, the hard-command unit and the OBDH system. Although we can report a flawless function of all the purchased subsystems in-orbit, the detailed in-house system-level testing of these components is a major lessons learned of First-MOVE from the prospective of student education and system knowledge. Despite the existence of documentation, the time and knowledge needed for designing a test bed for the electric power system (EPS) and the subsequent testing was underestimated. Furthermore, from a testing prospective, the importance of integrated system-level testing and the need for longer, continuous operations test of the satellite are emphasized. On-orbit flight data, as well as educational lessons learned for efficient student involvement during mission operations are highlighted. An outlook to MOVE II, the follow-up satellite project of LRT, outlines how the lessons learned of the last generation students can be carried over and how they will influence future (student) satellite developments and spaceflight development processes at LRT.
Cosmic antimatter is an excellent probe for many astrophysical processes. The abundancies and energy spectra of antiparticles help to understand the creation and propagation mechanisms of cosmic ray particles in the universe. The flux of geomagnetically trapped antiprotons in Earth’s inner radiation belt can help to verify our models of the production of secondary cosmic ray parti- cles and their motion in Earth’s magnetic field. The Antiproton Flux in Space (AFIS) experiment will measure this flux using a novel CubeSat-sized particle detector. This active-target detector consists of 900 scintillating fibers read out by silicon photomultipliers and is sensitive to antipro- tons in the energy range below 100 MeV. It has a large geometrical acceptance of about 250 cm2 sr because of its isotropic acceptance for particles. The particle identification scheme for antiprotons relies on a combination of Bragg curve spectroscopy and the characteristics of the annihilation process. In order to verify the detection principle, a prototype detector with a reduced number of channels was tested at a stationary proton beam. Its energy resolution was found to be less than 1 MeV for stopping protons of about 50 MeV energy. We give an overview of the AFIS mission and explain the working principle of the detector. We also discuss the results from the beam test.
The INTEGRAL satellite extensively observed the black hole binary Cygnus X-1 from 2002 November to 2004 November during calibration, open time and core program (Galactic Plane Scan) observations. These data provide evidence for significant spectral variations over the period. In the framework of the accreting black hole phenomenology, the source was most of the time in the Hard State and occasionally switched to the so-called "Intermediate State". Using the results of the analysis performed on these data, we present and compare the spectral properties of the source over the whole energy range (5 keV - 1 MeV) covered by the high-energy instruments on board INTEGRAL, in both observed spectral states. Fe line and reflection component evolution occurs with spectral changes in the hard and soft components. The observed behaviour of Cygnus X-1 is consistent with the general picture of galactic black holes. Our results give clues to the physical changes that took place in the system (disc and corona) at almost constant luminosity during the spectral transitions and provide new measures of the spectral model parameters. In particular, during the Intermediate State of 2003 June, we observe in the Cygnus X-1 data a high-energy tail at several hundred keV in excess of the thermal Comptonization model which suggests the presence of an additional non-thermal component. Comment: accepted for publication in A&A, 13 pages, 9 figures (3 in colour)
The recent and significant enlargement of aerospace research at the Technical University of Munich presents a unique opportunity to forge synergistic and enduring ties within the aerospace community in Munich and beyond. By establishing a multi-institutional Space Missions Laboratory dedicated to a broad field of disciplines—ranging from astrophysics over Earth observation to planetary science—we aim to foster world-class interdisciplinary research in a collaborative environment.
Nanosatellites are often controlled by a monolithic
command and data handling system. The Distributed Operating
System Initiative for Satellites (DOSIS) framework enables controlling a satellite in a distributed and modular fashion. In this
paper we present our approach to inter-process communication
of software components in a network of micro controller unit
(MCU) based nodes. The DOSIS framework implements the
interfacing of software components using message-based communication. The framework aims to reduce constraints for locality of software components within the network. We show that
using DOSIS, timing constraints in the sub-millisecond range
can be fulfilled in a distributed setup using a shared Controller
Area Network (CAN) bus. The timing precision is reached by
reliably synchronizing the time within the network using only
the CAN bus. As an example of a network inside a nanosatellite,
we simulate a control loop with sensor, controller and actor, each
handled by a different MCU. We verify our results by running
worst-case scenarios in benchmarks on a three node test setup.
In this paper we present Cubed OS, a lightweight application framework for CubeSat flight software. CubedOS is written in SPARKand proved free of certain classes of runtime errors. It consists of a collection of interacting, concurrent modules that communicate via message passing over a microkernel based on Ada's Ravenscar tasking model. It provides core services such as, for example, communication protocol processing and publish/subscribe message handling. Application-specific modules can be added to provide both high level functions such as navigation and power management, as well as low level device drivers for mission-specific hardware.
This paper will describe the development and testing of a new ARM© Cortex©-M based microcontroller for high temperature electronic systems. High temperature and electrical overstresses can cause latch-up in CMOS devices that will interfere with normal device operation or destroy the device. For reliable operation in the downhole drilling environment it was necessary to immunize this device against latch-up using an innovation processing technique. HARDSIL® technology that allows reliable latch-up free operation at extreme temperatures will be described. Details on the qualification and testing of the product to ensure that it meets the challenging environment will also be discussed. This includes electrical testing and temperature cycling testing to ensure that the different package options for the silicon device are mechanically sound in a high temperature environment that exposes the silicon and packaging materials to thermal cycling. The ecosystem for the microcontroller will also be discussed – hardware and software development tools are required to optimize the use of the device in extreme temperature embedded systems. An ecosystem of components is also required to operate with the microcontroller in the high temperature harsh environment.
RODOS is a real-time embedded operating system designed for application domains demanding high dependability. The RODOS real-time kernel and middleware provide an integrated object-oriented framework to multitasking resource management and to the NetworkCentric communication infrastructure. The RODOS framework seeks to offer the simplest and smallest possible interface to user applications, while still providing all the required functionality and flexibility.
MOVE (Munich Orbital Verification Experiment) is a program of the Institute of Astronautics (LRT) at the Technische Universität
München (TUM), which aims on building pico-satellites with university students mainly for educational purposes. First-MOVE
shall create a robust platform as a starting point for sophisticated satellite missions of the institute in the future. In
the paper, the state of development is described, but emphasis is on the requirements for high reliability of the First-MOVE
satellite and how robustness drives the actual design of the satellite.
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