The Herschel Space Observatory (aka Herschel) is the next major astronomical observatory in the ESA science program. Herschel is currently planned to be launched in 2008, and will offer three years of routine science operations for the astronomical community, commencing approximately six months after the launch.

Herschel will target the far infrared and submillimetre universe and is intended to be a facility for the entire astronomical community. Approximately two thirds of the Herschel time available for conducting astronomical observations is open time, which will be allocated to the community through a traditional competitive proposal process.

A major fraction of the total observing time will be dedicated to so-called Key Programs. These programs should have the following characteristics:

• exploit unique Herschel capabilities to address (an) important scientific issue(s) in a comprehensive manner,
• require a large amount of observing time to be used in a uniform and coherent fashion, and
• produce a resulting well characterized dataset of high archival value.

It is clear that the scientific motivation for an observing programme needing a particularly large amount of observing time has to be particularly high and well motivated. The resulting dataset should be likely to be used by a broad community for a number of investigations of high scientific merit.

The Announcement of Opportunity (AO) for Key Program observing proposals is to be issued on 1 February 2007, and the deadline of the Open Time Key Program proposal submission is set for 25 October 2007. The reserved observations of the Guaranteed Time Key Programs will be officially communicated on 5 July 2007, but the preliminary program contents will be broadly known and communicated by the time of the workshop.