**N. J. Elton**

Light deflection and polarisation rotation in gravitational fields

*1988 (supervisor: A. M. Cruise)*

This thesis is broadly divided into two parts linked by the common theme of the behaviour of electromagnetic radiation in gravitational fields.

A review of gravitational waves is presented containing background information useful in subsequent chapters. The effects of plane gravitational waves on various properties of electromagnetic radiation are investigated using geometric optics and the concept of parallel propagation and it is shown how the gravitational wave can produce a rotation of the plane of polarisation, deflection of the light ray, fluctuations in intensity and a redshift. The order of magnitude of these effects is estimated for a range of potential sources of gravitational waves.

The calculation is repeated using a realistic model for the gravitational waveforms for a particular class of sources (binary interactions). A numerical integration scheme is described and the basic results presented and compared with the plane wave formalism. The time behaviour of the various effects of the gravitational wave is also investigated.

Finally in Part One the effects of gravitational radiation on the properties of extended beams of photons are considered and the net polarisation rotation and intensity change calculated for some specific geometries. A model of a massive black hole accretion system is considered in some detail as a possible candidate for producing measurable effects.

In Part Two a description is given of the HIPPARCOS astrometric satellite together with an overview of the data reduction. Two specific data reduction tasks are considered in some detail and a simulation of the satellite's star observation strategy is described.

The final chapter briefly reviews solar system light deflection and the use of HIPPARCOS in testing the predictions of general relativity. An alternative scheme for extracting the relativistic content of the HIPPARCOS data is presented and evaluated.