Problems of antenna measurement in the terahertz frequency range

A new generation of scientific instruments is under consideration at millimetre and submillimetre wavelengths which include both earth observation and scientific missions. In the current generation of earth observation studies, there are millimetre and submillimetre limbsounding instruments (for example, MASTER and SOPRANO). Astronomy missions are also projected in which the frequency range may extend to above 3 THz. Because of the high gain and high frequency of these instruments, testing and proving the antennas and their associated feed systems present problems which require special attention. A study funded by ESTEC is currently under way to examine possible measurement techniques and to recommend a cost-effective solution. This paper sets out the measurement requirements and highlights the accuracy required of any facility finally implemented. The problem areas identified to date are listed