The attitude determination and control subsystem is used to control the orientation of a satellite. The first task of the subsystem is to estimate the current attitude (or orientation) of the satellite using a number of different estimator algorithms, each employing a unique combination of sensor measurements. These sensors include magnetometers, sun sensors, nadir (or Earth) sensors, and star trackers. Thereafter the attitude controllers command reaction wheels, control moment gyroscopes (CMGs) or magnetic torquers to control the satellite’s attitude to a certain desired orientation.
The aim of this project is to design, build, and test an horizon sensor that can determine the attitude of a CubeSat. This will form part of the ACDS system of the satellite. The sensor will estimate the satellite’s attitude by searching for the horizon with the use of an infrared camera, and determine the attitude accordingly. An infrared camera will be used – instead of a normal camera – to ensure constant attitude estimation, even when in eclipse. A normal camera needs visible light to function of which there is almost none in eclipse, while the infrared camera will be able to see the warm Earth distinctly against cold space.
The aim is to develop a conceptual satellite that combines the scalability and stability of a spinning sail with the agility of a 3-axis stabilized sail. A tri-spin satellite is proposed making use of a spinning sail and a momentum countering system (MCS) rotating relative to the satellite body. The MCS reduces the angular momentum bias increasing the manoeuvrability of the satellite. Induced oscillations in the non-rigid elements due to attitude changes are investigated. A complete attitude determination and control system (ADCS) for such a satellite in an earth-centred orbit is proposed and simulated. The simulation reveals that the tri-spin concept is viable.
Accurate on-board position knowledge is crucial for most satellite missions. As a GPS module constantly operating can cripple the power budget of a nanosatellite, most missions make use of propagators to estimate position. The power budget can be significantly lightened by having the GPS module activate for only a small segment of each orbit. On-board propagators are limited by imperfect disturbance force models (like aerodynamic drag), as well as the on-board computer capability shortcomings. This project entails the development of a propagator method, based on either existing analytical (SGP4) or numerical techniques, which correctly updates its state and disturbance force models by using GPS measurements for only a short segment of the satellite’s orbit.
Attitude Determination and Control System (ADCS) is the most critical subsystem of a Satellite and is responsible for the basic payload and bus operations of the mission .This research work includes the design of a complete ADCS for a 12-U Nanosatellite based on the ADCS hardware developed at Electronics System Laboratory (ESL).The scope of this work also includes the Hardware design for Magnetic and Reaction Wheels Control Electronics. Moreover, a complete integrated ADCS is to be tested on an air bearing table placed inside the Helmholtz Cage System with a Sun Simulator. Attitude is to be determined from the Magnetic Field and Sun direction vectors and several Magnetic and Reaction Wheel Controllers are to be tested in Hardware in the Loop Environment.