Spring Semester

Components of Assessment	Method(s)	Percentage Weighting
Coursework	Assignment	20%
Examination	Written, closed-book, (2 hours).	80%

EEM.ssd Spacecraft System Design

To develop an understanding of the complexities of real satellite dynamics and practical methods to determine and control spacecraft motions.

By the end of the module, the student will

• have an appreciation of real satellite orbits and how to model them.
• be able to apply these models to problems of rendezvous in space and the use of GPS in Space navigation for LEO, with exploration of estimation techniques for attitude and orbit. 
• have a detailed understanding of attitude sensors and actuators and develop real world control algorithms used for attitude control.

Over view of Satellite Orbits: 

Review of Keplerian orbits and the most useful orbits for Earth orbiting satellites. Brief introduction to time and coordinate frames and the complexity of their definition.

Perturbation Effects in Real Orbits: 

Mean and osculating elements, the disturbing function and Lagrange’s equations. Long and short periodic variations and secular evolution. Atmospheric drag modelling. Effects of Solar radiation pressure.

Rendezvous in Space: 

Non-coplanar rendezvous – the International Space Station. Continuous thrust manoeuvres. Relative motion and Hill’s formulation. Epicycle description.- inclusion of perturbing influences. Guidance and optimisation of trajectories. Orbit control.

Principles of GPS Navigation: 

GPS network, triangulation solution, pseudoranges, carrier phase, dilution of precision, error sources (line bias, mulitpath, ionospheric delays). Predicting rise and set times and look angles. Alternatives – Glonass and Galileo.

Orbit Determination and Estimation Methods: 

linear least squares, weighted least squares, nonlinear least squares – probabilistic interpretation. Application to orbit determination with differential corrections. Batch filters and recursive filters. The Kalman filter.

Attitude Dynamics: 

Euler and the kinematic equations. Quaternions and the evolution equations. Control Moment Gyroscopes with emphasis on 2 wheel systems – the BilSat example.

Attitude Determination and Estimation: 

vector observations, Triad and Quest algorithms. Sensors: sun sensors, star cameras. Star trackers, horizon sensors, gyroscopes – the laser gyro, accelerometers.

Attitude Control: 

Actuators on a satellite: momentum and reaction wheels, gravity gradient booms, control moment gyroscopes, thrusters, magnetorquing. Advantages and limitations. Flexible structures and normal modes. Real world spacecraft attitude control – detumbling, Y-Thomson spin. Design of the control loop.

Teaching is by lectures and tutorials. Learning takes place through lectures, tutorials, exercises and coursework. 3 hours lectures/tutorials/examples classes per week for 12 weeks.

M. J. Sidi, Spacecraft Dynamics and Contorl, Cambridge Aerospace Series, 1997

D. Vallado Fundamentals of Astrodynamics & Applications, Kluwer, 2001.

O. Montenbruck and E. Gill Satellite Orbits: Models, Methods & Applications, Springer-Verlag, 2000.

15th August 2006