FUNDAMENTALS OF SPACE SYSTEMS
Credits: 12
Learning objectives
Part 1 - Navigation (6 credits)
The concept of navigation. Fixing vs. deduced reckoning. Different classes of navigation. Time and space reference frames. Reporting navigation solution: fundamentals of cartography and geodesy. Navigation in real time vs. trajectography. Navigation as an element of the Guidance-Control-Navigation loop. Effects of navigation accuracy on system performance.
Navigation instruments. Characteristics and metrological properties of the sensors. Basics of probability and statistics.
Improving the navigation solution. Filtering techniques. Linear and Extended Kalman Filter. Unscented Kalman Filter. Particle Filter. Integrated navigation.
Satellite-based navigation. From TRANSIT (Doppler-count) to time-of-arrival systems. Pseudorange, linearized solution, effects of geometry, expected budget error. GPS, GLONASS, Galileo and Beidou systems: similarities and differences. Differential navigation and augmentation systems. GPS experiments with lab’s test bed.
Inertial Navigation. Stable platforms and strap-down architectures. Accelerometers and gyroscopes. MEMS. Optical gyros. Attitude reconstruction. Mechanizations. Instability. Experiments with lab’s test bed.
Visual-based navigation. Feature recognition and Hough transform techniques. Experiments with lab’s test bed.
Terrestrial applications: road vehicles and railways. Navigation and telematics. Marine applications: typical solutions in extreme weather and berthing. Aeronautical applications: from classical ground-based RF aiding (LORAN, VOR, DME, ILS) to satellite-based techniques. Procedural vs. free route navigation.
Space applications. Launchers’ navigation systems. Orbit determination in LEO and GEO. GNSS-based attitude determination. Tracking deep-space probes. The case for lunar missions.
Part 2 - Attitude determination and control of space vehicles (6 credits)
The course aims at providing students with the tools necessary to address the study of the subsystem attitude control of a spacecraft . In particular , the main objective is to provide the elements for the definition of the control system according to the requirements of the mission. The content of the Course is the following. Review of attitude dynamics and kinematics. Elements of Control Theory and Estimation. Control systems, continuous-time and discrete time ; Sequential estimation of the state ; Estimate batch status ; Kalman filter in the presence of white and colored noise. Sensors and Actuators: Sun and Earth sensors, Star sensors. Gyroscopes and magnetometers ; Characterization of the noise of the sensors ; Wheels of inertia ; Reaction wheels ; Jet engines ; Magnetic actuators ( magnetorquer ) . Control Moment Gyro ( CMG ) . Characterization of disorders of the actuators. Methods for attitude determination: Deterministic methods ; Statistical method ; Estimation methods based on quaternion and Rodrigues parameters; Techniques of data fusion. Technical digital multi-rate. Attitude Control Subsystem: attitude control architectures; Techniques to control linear and nonlinear systems ; Analysis of the closed loop system , Sensors and Actuators modeling. Characterization of the disturbance torques of the space environment . Notes on Control of Flexible Space Vehicles, Problem of spillover in the control system ; Attitude control and vibration .