| 1. |
- Browne Mwakyanjala, Moses, 1986-
(författare)
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A Software-Defined Baseband for Satellite Ground Operations : Feasibility and Design
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Satellite telemetry, tracking, and command (TT&C) is a crucial activity needed to maintainthe health of a spacecraft or sometimes to facilitate payload data download. TT&Cground operations are facilitated by a communication device known in the TT&C communityas a baseband. State-of-the-art baseband systems currently in the market haveseveral financial and technical limitations. Financial drawbacks include high capital expenditure,operational expenditure, maintenance costs, and high upgrade costs, whiletechnical limitations include both upgradability and scalability.This thesis presents the feasibility study of a software-defined baseband (SDB) as aviable alternative to existing basebands. The SDB considered here is implemented on aradio architecture that consists of a general-purpose processor for performing radio functionsand low-cost commercial-off-the-shelf, software-defined radio frontends for signalsampling. The research questions focus on the feasibility and design aspects of this SDB.This thesis approaches the design of the SDB with a software development cyclethat involves functional analysis (design), verification, and validation of the radio functionsconstituting the SDB system. The radio functions are the telemetry receiver andthe telecommand transmitter. Functional analysis is performed through functional flowblock diagrams. The verification process is performed through simulations that take intoaccount realistic channel impairments for missions operating in the S-band and characterizedby the Consultative Committee for Space Data Systems (CCSDS) as category Amissions (less than 2 million km). Validation is performed on a laboratory testbed andseveral orbiting satellites.Through the above software development cycle, the telemetry receiver and telecommandtransmitter are developed using the open-source GNU radio development kit. Modulationschemes, line codes, and filters along with CCSDS forward error correction codescommonly employed in TT&C communications are successfully designed, verified in simulations,and validated in a hardware testbed. The performance results from the validationtests demonstrate that it is feasible to implement the SDB TT&C radio functions on theadopted radio architecture.Finally, this thesis investigates in detail the novel concept of multiple spacecraft peraperture (MSPA) that enables communication with several spacecraft from a single antenna.It focuses on in-band interference and out-of-band emissions arising from radiatingmultiple telecommand links from a low-cost SDR frontend. An MSPA transceiver is successfullydeveloped and integrated into the SDB system. Validation tests show that itis feasible for the integrated MSPA transceiver to radiate two telecommand links whileconforming to spectral regulations.
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| 2. |
- Browne Mwakyanjala, Moses, et al.
(författare)
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Feasibility of using a software-defined baseband for multiple space per aperture (MSPA) ground operations
- 2022
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Ingår i: International Journal of Satellite Communications And Networking. - : John Wiley & Sons. - 1542-0973 .- 1542-0981. ; 40:2, s. 133-147
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the feasibility of performing multiple spacecraft per aperture (MSPA) ground operations by using a low-cost software-defined baseband (SDB). The SDB is a Consultative Committee for Space Data Systems (CCSDS)-compliant baseband that employs a personal computer for signal processing and a low-cost commercial-off-the-shelf RF front end for RF signal sampling. The SDB is customized to offer traditional telemetry, tracking, and command (TT&C) services for near-Earth missions operating in S band. The study starts by reviewing MSPA methods already studied by space agencies such as NASA and ESA before going to MSPA methods proposed in the latest CCSDS blue book on RF and modulation systems. The feasibility of operating the CCSDS-proposed multiple uplink carrier MSPA method using the SDB is assessed after evaluating in-band interference and out-of-band emissions from the uplink signals radiated by the low-cost RF front end employed by the SDB. Furthermore, we present a case study where the SDB is used in MSPA operations on a typical solid-state amplifier (SSPA) amplifier typically used in near-Earth missions.
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| 3. |
- Browne Mwakyanjala, Moses, et al.
(författare)
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Validation of a software-defined baseband system for satellite telemetry and telecommand
- 2021
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Ingår i: International Journal of Satellite Communications And Networking. - : John Wiley & Sons. - 1542-0973 .- 1542-0981. ; 39:6, s. 605-625
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the validation of a software-defined baseband (SDB) system for satellite telemetry and telecommand (TM/TC). The baseband system was developed using the open-source GNU Radio development kit. It runs on a personal computer connected to a commercial-off-the-shelf (CoTS) RF frontend. The validation process was performed by the use of a mission-qualified satellite emulator, a state-of-the-art baseband unit, and orbiting satellites. The baseband is designed to offer multimission support. Hence, it includes a suite of modulation schemes, line codes, matched filters, and Consultative Committee for Space Data Systems (CCSDS) forward error correction codes (convolutional, Reed–Solomon, concatenated, and low-density parity-check [LDPC]) typically employed in TM/TC missions. The figures of merit used for the validation of the TM receiver are bit error rate (BER) and frame error rate (FER). For the TC transmitter, the validated features are modulation index, power spectrum, and the physical layer operations procedures (PLOP).
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| 4. |
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| 5. |
- Cha, Jihyoung, 1988-, et al.
(författare)
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Performance Comparison of Control Strategies for a Variable-Thrust Solid-Propellant Rocket Motor
- 2022
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Ingår i: Aerospace. - : MDPI. - 2226-4310. ; 9:6
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with a performance comparison of the control algorithm for a variable-thrust solid-propellant rocket motor (VTSRM). To do this, we develop a simulation model of a VTSRM considering characteristic changes in the combustor and design control systems for pressure and thrust. We use three types of control algorithms for the pressure control: classical PID control, feedback linearization control, and fuzzy PID control, and two control algorithms for thrust control: classical PID control and fuzzy PID control. Finally, we compare the performance of each control system through a numerical simulation using step responses. Through this work, we check that feedback linearization is better in pressure control, and fuzzy PID control is more appropriate in thrust control. Especially using fuzzy PID control, we can get fast settling with a small undershoot even if the system is a nonminimum phase system.
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| 6. |
- de Oliviera, Élcio Jeronimo, et al.
(författare)
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Brazilian Suborbital Rockets for Hypersonic Flight Testing : A Review and a Market Perspective
- 2019
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Ingår i: IAC-19. - : International Astronautical Federation.
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Konferensbidrag (refereegranskat)abstract
- Hypersonic flight testing in real flight conditions is crucial to mature hypersonic technologies including scramjet engines, high-speed vehicles, high-temperature materials and autonomous flight control. Brazilian suborbital rockets made by Institute of Aeronautics and Space (IAE) have provided frequently to the hypersonic research community affordable access to high Mach number in endoatmospheric flight conditions. For instance, IAE provided hypersonic flight-testing capabilities for fundamental research and technological development of SHEFEX, HIFiRE, and ScramSpace programs by using the vehicles VS-30/Orion, VSB-30 and VS-40 in a total of eight launch missions (from 2005 to 2017). Future launches, among others, include flight testing of a scramjet engine in 2020 by using a hypersonic accelerator vehicle, based on the suborbital rocket VSB-30, under the Brazilian hypersonic research project 14-X. Especially, the ground-launched two-stage solid rocket VSB-30has demonstrated to be technically very suitable and reliable for hypersonic flight research and development at flight Mach number up to 7 into the stratosphere zone. This review paper gives both successes and failures cases studies of hypersonic flight testing already powered by IAE suborbital solid rockets, discusses about the current Brazilian suborbital rocket motors capabilities in terms of possible configurations and approaches to offer extreme hypersonic flight conditions including their flight dynamics, and addresses some commercial perspectives of utilizing them in hypersonic flight testing oriented by practical lessons learned from such cases studies.
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| 7. |
- Nieto Peroy, Cristóbal, et al.
(författare)
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A Concurrent Testing Facility Approach to Validate Small Satellite Combined Operations
- 2021
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Ingår i: Aerospace. - : MDPI. - 2226-4310. ; 8:12
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Tidskriftsartikel (refereegranskat)abstract
- Federated remote laboratories allow for the execution of experiments ex situ. The coordination of several laboratories can be used to perform concurrent experiments of combined space operations. However, the latency of the communications between facilities is critical to performing adequate real-time experiments. This paper presents an approach for conducting coordinated experiments between floating platforms at two remote laboratories. Two independently designed platforms, one at Luleå University of Technology and the other at La Sapienza University of Rome, were established for this purpose. A synchronization method based on the Simple Network Time Protocol was created, allowing the offset and delay between the agents to be measured.Both platforms exchange data about their measured time and pose through a UDP/IP protocol over the internet. This approach was validated with the execution of simulated operations. A first demonstrative experiment was also performed showing the possibility to realize leader/follower coordinated operations. The results of the simulations and experiments showed communication delays on the order of tens of milliseconds with no significant impact on the control performance. Consequently, the suggested protocol was proven to be adequate for conducting coordinated experiments in real time between remote laboratories.
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| 8. |
- Nieto-Peroy, Cristóbal, et al.
(författare)
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A hardware-in-the-loop simulation testbed for validation of small satellite technologies
- 2021
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Konferensbidrag (refereegranskat)abstract
- This paper presents the research that is being conducted with the hardware-in-the-loop simulation testbed laying at the Nano Satellite Lab at the Kiruna Space Campus of Luleå University of Technology. Particularly, a brief introduction to the frictionless platform and both robot manipulators that comprise such a testbed is given. Additionally, this paper summarizes the simulations that are currently performed on the testbed. Finally, the paper also discusses some future activities that are planned to be conducted to improve the way systems and components of small satellites are currently validated.
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| 9. |
- Nieto-Peroy, Cristóbal
(författare)
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Concurrent Engineering of Small Satellites using Hardware-in-the-loop Simulations
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The miniaturization of spacecraft has brough the possibility of conducting space missions to a vast portion of private enterprises and scientific institutions. The inaccessibility of modest developers to the resources that governmental agencies and primary contractors utilize to develop conventional satellites has not been an obstacle for them to apply different, more agile and risk-seeking approaches. However, the failure rate of Small Satellite missions has increased to a higher degree than the total number of missions, particularly if only CubeSats are considered.The research conducted in this thesis proposes an improvement to the development of space systems by focusing on the verification and validation processes. For that, the thesis revolves around two main areas. First, the thesis deals with the engineering methodology. The notions of concurrent engineering are generalized and combined with the test-driven development and behavior-driven development methodologies to perform the parallel, yet integrated, development of the various spacecraft subsystems that can be at different maturity levels. For example, these processes have been applied in-house to the development of onboard computers and telecommunication systems. The proposed methodology allows for the automation of the engineering workflow and the early detection and correction of defects in the system by frequently testing it along the process.Secondly, the research also deals with the development and utilization of a simulation environment that fits the proposed methodology. The thesis provides advancements on hardware-in-the-loop simulation techniques with a particular focus on frictionless platforms. Such a platform can perform, but is not limited to, dynamic simulations. Additionally, the thesis also provides the characterization of the platform to use it as a reference for comparison with other similar ones.All in all, the simulation environment has demonstrated to provide the versatility needed by the methodology. Such environment has served as a platform to develop different subsystems from the simulation of physical models to the testing of actual hardware prototypes. Two studies are provided as examples of such accomplishments, i.e., a study with the remote simulation of cooperative maneuvers and a different one with the development of flexible appendages for a spacecraft.
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| 10. |
- Nieto-Peroy, Cristóbal, et al.
(författare)
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Simulation of Spacecraft Formation Maneuvers by means of Floating Platforms
- 2021
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Ingår i: 2021 IEEE Aerospace Conference (50100). - : IEEE.
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Konferensbidrag (refereegranskat)abstract
- This article provides a proposal case for studying simulations of spacecraft formation maneuvers in a Hardware-in-the-Loop Simulation Testbed specifically devoted to nanosatellites. The design specifications of the setup to perform such simulations are given, as well as the methods and results of the preliminary characterization of the floating platform to be used. The intent is to create a corpus of tests to find the dynamic behavior in a frictionless simulation as part of a concurrent decentralized simulation between the NanoSat Lab in Luleå University of Technology and the Guidance and Navigation Lab at La Sapienza.
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