The development of a small spacecraft attitude determination and control subsystem is described. This subsystem is part of The Space Flight Laboratory's Generic Nanosatellite Bus. With a 20cm3 body, the bus has an attitude determination and control subsystem capable of full three-axis stabilization and control enabling more advanced missions previously only possible with bulkier and more power-consuming attitude control hardware. Specific contributions to the Space Flight Lab's attitude control hardware are emphasised. Particularly, the full development of a 32g three-axis nanosatellite rate sensing unit is described. This includes embedded software development, skew calibration, hardware modeling and qualification testing for the unit. Development work on a three-axis boom-mounted magnetometer is also detailed. A full hardware design is also described for a new microsatellite-sized rate sensor. Larger and more powerful than the nanosatellite rate sensors, the design ensures a low noise, low drift architecture to improve attitude determination on future microsatellite missions.

Contributions to two missions are presented. The first is a demonstration mission called CanX-7 that uses a 4 square metre drag sail to de-orbit a 3.5 kg satellite. In order to estimate the effectiveness of the drag sail, a novel method is developed that takes into account the time-varying nature of the projected drag area. The Space Flight Laboratory designed drag sail is shown to be sufficient to de-orbit the CanX-7 spacecraft within the 25 year requirement. The Antarctic Broadband demonstrator spacecraft is a 20 cm cubical nanosatellite that will demonstrate the feasibility of a Ka-band link between the research community in Antarctica and stakeholders in Australia. In support of this mission, a passive thermal control subsystem is designed that will keep all the components within their operational temperature limits at all times throughout the mission.

The development of a small spacecraft attitude determination and control subsystem is described. This subsystem is part of The Space Flight Laboratory's Generic Nanosatellite Bus. With a 20cm3 body, the bus has an attitude determination and control subsystem capable of full three-axis stabilization and control enabling more advanced missions previously only possible with bulkier and more power-consuming attitude control hardware. Specific contributions to the Space Flight Lab's attitude control hardware are emphasised. Particularly, the full development of a 32g three-axis nanosatellite rate sensing unit is described. This includes embedded software development, skew calibration, hardware modeling and qualification testing for the unit. Development work on a three-axis boom-mounted magnetometer is also detailed. A full hardware design is also described for a new microsatellite-sized rate sensor. Larger and more powerful than the nanosatellite rate sensors, the design ensures a low noise, low drift architecture to improve attitude determination on future microsatellite missions.

Contributions to two missions are presented. The first is a demonstration mission called CanX-7 that uses a 4 square metre drag sail to de-orbit a 3.5 kg satellite. In order to estimate the effectiveness of the drag sail, a novel method is developed that takes into account the time-varying nature of the projected drag area. The Space Flight Laboratory designed drag sail is shown to be sufficient to de-orbit the CanX-7 spacecraft within the 25 year requirement. The Antarctic Broadband demonstrator spacecraft is a 20 cm cubical nanosatellite that will demonstrate the feasibility of a Ka-band link between the research community in Antarctica and stakeholders in Australia. In support of this mission, a passive thermal control subsystem is designed that will keep all the components within their operational temperature limits at all times throughout the mission.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The ability of satellites to actively control their attitude has changed the way we live. Navigation systems, satellite television, and weather forecasting, for example, all rely on satellites which are able to determine and control their attitude accurately. This project was aimed at designing and analysing an attitude determination and control system (ADCS) for a 20 kg Earth observation satellite by means of simulation. A realistic simulation toolset, which includes the space environment, sensor, and actuator models, was created using MATLAB and Simulink. An ADCS hardware suite was selected for the satellite based on a given set of pointing and stability requirements, as well as current trends in the small satellite industry. The hardware suite consists of among others a star tracker and three reaction wheels. A variety of estimators and controllers were investigated, after which an application specific ADCS state machine was defined. The state machine included a Safe Mode for de-tumbling, a Nominal Mode for normal operation, a Forward Motion Compensation (FMC) Imaging Mode for Earth observation, and a Target Tracking Mode for ground station tracking. Simulation results indicated that de-tumbling, coarse and fine sun tracking, FMC factor 4 imaging, and target tracking were successfully implemented. Lastly, the satellite’s pointing error and stability were determined to be less than 70 arcseconds and 7 arcseconds per second respectively, both values well within the given requirements. / AFRIKAANSE OPSOMMING: Satelliete se vermoë om hul oriëntasie aktief te beheer, het die manier waarop ons lewe, verander. Navigasiestelsels, satelliettelevisie en weervoorspelling, byvoorbeeld, maak staat op satelliete wat hul oriëntasie akkuraat kan bepaal en beheer. Die mikpunt van hierdie projek was die ontwerp en analise van ’n oriëntasiebepaling- en -beheerstelsel (ADCS) vir ’n 20 kg aardwaarnemingsatelliet deur middel van simulasie. ’n Realistiese simulasieopstelling, wat modelle van die ruimteomgewing, sensore en aktueerders insluit, was ontwikkel deur gebruik te maak van MATLAB en Simulink. ’n ADCS hardewarestel was gekies vir die satelliet op grond van ’n stel rig- en stabiliteitsvereistes, sowel as die huidige tendense in die klein-satellietbedryf. Die hardewarestel bestaan onder andere uit ’n stervolger en drie reaksiewiele. Nadat verskeie afskatters en beheerders ondersoek was, was ’n toepassingspesifieke ADCS toestandmasjien gedefinieer. Die toestandmasjien het ’n Veilige Modus vir onttuimelling, ’n Nominale Modus vir normale operasie, ’n Vorentoe-bewegingskompensering (FMC) Beeldskandeermodus vir aardwaarneming en ’n Teikenvolgmodus vir grondstasie volging ingesluit. Simulasieresultate het aangedui dat onttuimeling, growwe- en fyn sonvolging, FMC faktor 4 beeldskandering en teikenvolging suksesvol geïmplementeer was. Laastens was die satelliet se rigfout en stabiliteit bepaal as minder as 70 boogsekondes en 7 boogsekondes per sekonde onderskeidelik, albei waardes gemaklik binne die vereistes.

The Generic Nanosatellite Bus (GNB) is a spacecraft platform designed to accommodate the integration of diverse payloads in a common housing of supporting components. The development of the GNB at the Space Flight Laboratory (SFL) under the Canadian Advanced Nanospace eXperiment (CanX) program provides accelerated access to space while reducing non-recurring engineering (NRE) costs. The work presented herein details the development of the attitude determination and control subsystem (ADCS) of the GNB. Specific work on magnetorquer coil assembly, integration, and testing (AIT) and reaction wheel testing is included. The embedded software development and unit-level testing of the GNB sun sensors are discussed. The characterization of the AeroAstro star tracker is also a major focus, with procedures and results presented here. Hardware models were developed and incorporated into SFL's in-house high-fidelity attitude dynamics and control simulation environment. This work focuses on specific contributions to the CanX-3, CanX-4&5, and AISSat-1 nanosatellite missions.

The Generic Nanosatellite Bus (GNB) is a spacecraft platform designed to accommodate the integration of diverse payloads in a common housing of supporting components. The development of the GNB at the Space Flight Laboratory (SFL) under the Canadian Advanced Nanospace eXperiment (CanX) program provides accelerated access to space while reducing non-recurring engineering (NRE) costs. The work presented herein details the development of the attitude determination and control subsystem (ADCS) of the GNB. Specific work on magnetorquer coil assembly, integration, and testing (AIT) and reaction wheel testing is included. The embedded software development and unit-level testing of the GNB sun sensors are discussed. The characterization of the AeroAstro star tracker is also a major focus, with procedures and results presented here. Hardware models were developed and incorporated into SFL's in-house high-fidelity attitude dynamics and control simulation environment. This work focuses on specific contributions to the CanX-3, CanX-4&5, and AISSat-1 nanosatellite missions.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006. / An analysis of the attitude determination and control system required for a small geostationary satellite is performed in this thesis. A three axis quaternion feedback reaction wheel control system is the primary control system used to meet the stringent accuracy requirements. A momentum bias controller is also evaluated to provide redundancy and to extend actuator life. Momentum dumping is preformed by magnetic torque rods using a crossproduct controller. Performance of three axis thruster control is also evaluated. A full state Extended Kalman filter is used to determine attitude and body angular rates during normal operation whereas a Multiplicative Extended Kalman Filter is used during attitude manoeuvres. An analytical orbit control study is also performed to calculate the propellant required to perform station-keeping, for a specific sub-satellite location over a ten year period. Finally an investigation on the effects caused by thruster misalignment, on satellite attitude is also performed.

The analysis, verification and emulation of attitude control hardware for nanosatellite spacecraft is described. The overall focus is on hardware that pertains to a multitude of missions currently under development at the University of Toronto Institute for Aerospace Studies - Space Flight Laboratory. The requirements for these missions push the boundaries of what is currently the accepted performance level of attitude control hardware. These new performance envelopes demand new acceptance test methods which must verify the performance of the attitude control hardware. In particular, reaction wheel and hysteresis rod actuators are the focus. Results of acceptance testing are further employed in post spacecraft integration for hardware emulation. This provides for a reduced mission cost as a function of reduced spare hardware. The overall approach provides a method of acceptance testing to new performance envelopes with the benefit of cost reduction with hardware emulation for simulations during post integration.

The analysis, verification and emulation of attitude control hardware for nanosatellite spacecraft is described. The overall focus is on hardware that pertains to a multitude of missions currently under development at the University of Toronto Institute for Aerospace Studies - Space Flight Laboratory. The requirements for these missions push the boundaries of what is currently the accepted performance level of attitude control hardware. These new performance envelopes demand new acceptance test methods which must verify the performance of the attitude control hardware. In particular, reaction wheel and hysteresis rod actuators are the focus. Results of acceptance testing are further employed in post spacecraft integration for hardware emulation. This provides for a reduced mission cost as a function of reduced spare hardware. The overall approach provides a method of acceptance testing to new performance envelopes with the benefit of cost reduction with hardware emulation for simulations during post integration.