Application of fixed delay Michelson interferometer for Radial Velocity measurement

Fixed Delay Michelson Interferometer (FDMI) also called Wide-Angle Michelson Interferometer (WAMI) is different from conventional Michelson interferometer. Its fixed delay is not only useful to widen the field of view, but also improve the accuracy of RV measurement. So it's widely known that works well on upper atmospheric wind study by measuring the Doppler shift of single emission lines. On the other hand, a new technique called External Dispersed Interferometry (EDI) can efficiently overcome the fundamental limitation of narrow bandpass of interferometer by combination between FDMI and post-disperser. The related instruments have been successfully used in the exoplanet exploration field. In this paper, the FDMI concept and its application in these two fields are reviewed, and a major astronomical project in China, which is developing a multi-object exoplanet survey system (MESS) based on FDMI, is introduced.