Imaging fourier transform spectroscopy

Fourier transform spectroscopy (FTS) is now well established as a powerful diagnostic tool in far-infrared and submillimetre spectroscopic applications. The high throughput of an FTS is of particular importance in this energy starved region of the electromagnetic spectrum. It has been recognized for many years that an FTS can be readily modified for imaging spectroscopic applications by simply placing a detector array at one of its outputs. The development of array detectors operating at optical wavelengths, which has been driven in part by the consumer market, has been impressive. Similar advances in the development of array detectors have occurred at longer wavelengths, with cost increasing monotonically with wavelength. In particular, recent advances in the production of large format, TES detector arrays (e.g. SCUBA-2) presents a new opportunity for imaging spectroscopic applications at submillimetre wavelengths. The underlying principles of imaging Fourier transform spectroscopy (iFTS) are reviewed, and the challenges facing this field discussed with respect to two iFTS systems (SPIRE and FTS-2) that have been developed for submillimetre astronomical applications.