The "Herschel Space Observatory" - the mission formerly known as FIRST - will perform photometry and spectroscopy in the 60-670 µm range. It will have a radiatively cooled telescope and carry a science payload complement of three instruments housed inside a superfluid helium cryostat. It will be operated as an observatory for a minimum of three years following launch and transit into a an orbit around the Lagrangian point L2 in the year 2007.

In April 2003 we submitted an application for an ESA fund to cover our participation in the Herschel project. We offered 8 man-years of effort for contribution to the pre-flight and in-flight calibration of the Photometer Array Camera and Spectrometer (PACS) instrument. The major tasks would be design of calibration procedures; analysis of test results; selection of celestial standards; and contribution to the establishment of the in-flight calibration plan. The planned start date of the project is September 2004.

A short Herschel mission overview

The `Herschel Space Observatory' (formerly known as FIRST) is the fourth cornerstone mission in the European Space Agency (ESA) science programme. It will perform imaging photometry and spectroscopy in the far infrared and submillimetre part of the spectrum, covering approximately the 60-670 µm range.

Herschel is the only space facility dedicated to the submillimetre and far infrared part of the spectrum. Its vantage point in space provides several decisive advantages, including a low and stable background and full access to this part of the spectrum.

Herschel has the potential of discovering the earliest epoch proto-galaxies, revealing the cosmologically evolving AGN-starburst symbiosis, and unraveling the mechanisms involved in the formation of stars and planetary system bodies. The key science objectives emphasise specifically the formation of stars and galaxies, and the interrelation between the two, but also includes the physics of the interstellar medium, astrochemistry, and solar system studies.

Herschel will carry a 3.5 metre diameter passively cooled telescope. The science payload complement - two cameras/medium resolution spectrometers (PACS and SPIRE) and a very high resolution heterodyne spectrometer (HIFI) - will be housed in a superfluid helium cryostat.

Herschel will be placed in a transfer trajectory towards its operational orbit around the Earth-Sun L2 point by an Ariane 5 (shared with Planck) in early 2007. Once operational FIRST will offer a minimum of 3 years of routine observations; roughly 2/3 of the available observing time is open to the general astronomical community through a standard competitive proposal procedure.

Herschel Science Instruments

The Herschel science payload has been conceived and optimised with the prime science goals in mind, but in addition it offers a wide range of capabilities for the `general' observer. It consists of three instruments selected on the basis of the response to an Announcement of Opportunity (AO) issued in October 1997. The Principal Investigators (PIs) and the instruments selected were:

• The Photodetector Array Camera and Spectrometer (PACS) instrument will be built by a consortium led by A. Poglitsch, MPE, Garching, Germany.
  
• The Spectral and Photometric Imaging REceiver (SPIRE) instrument will be built by a consortium led by M. Griffin, QMW, London, UK.
  
• The Heterodyne Instrument for the Far Infrared (HIFI) instrument will be built by a consortium led by Th. de Graauw, SRON, Groningen, The Netherlands.

The PI consortia provide the instruments to ESA under their own funding, in return for guaranteed observing time. The scientific payload complement was selected by the ESA Science Programme Committee in May 1998 and approved in February 1999.