HerMES is the Herschel Multi-tiered Extragalactic Survey, an astronomical project to study the evolution of galaxies in the distant Universe.It is the largest project on ESA's Herschel Space Observatory (900 hours). You will find more information about it on the HerMES website.
The project is carried out by a large team, made up primarily of people who built one of the
instruments on Herschel called
The locus of the HerMES fields is shown on the map below (click to enlarge).
The HerMES survey has a hierarchical structure containing 7 levels with increasing area but shallower coverage from very deep observations of clusters through levels 1-6 covering a total 70 square degrees.
You will find the list and position of currently released datasets on the download page.
The instrument used for the HerMES observations, SPIRE (Spectral and Photometric Imaging Receiver) instrument contains a three-band imaging photometer operating at 250µm, 360µm and 520µm, and an imaging Fourier Transform Spectrometer (FTS) covering 200-670µm.