Herschel is an ESA cornerstone observatory for the far infrared and submillimetre, covering roughly the 55-671 µm spectral range. Herschel has a 3.5 m diameter passively cooled low emissivity telescope, and a payload of three scientific instruments called HIFI, PACS, and SPIRE.

The instrument complement can perform imaging photometry in six broad bands, low- to medium resolution imaging spectroscopy, and very high resolution heterodyne spectroscopy across most of the Herschel spectral range. The instrument focal plane units are cryogenically cooled using a superfluid helium cryostat which gives the mission a finite lifetime.

More information about Herschel and its instruments can be found on the HSC website in general (see below) and in the five observers' manuals in the AO documentation package in particular.