The Herschel science payload comprises three instruments which have been conceived and optimised with the prime science goals in mind. The instruments offer a wide range of capabilities to cater for a wide and diverse range of observing programs. The instruments were selected from 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 is provided a consortium led by A. Poglitsch, MPE, Garching, Germany.
• The Spectral and Photometric Imaging REceiver (SPIRE) instrument is provided by a consortium led by M. Griffin, Cardiff University, UK.
• The Heterodyne Instrument for the Far Infrared (HIFI) instrument is provided by a consortium led by F. Helmich, SRON, Groningen, The Netherlands.

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

PACS is a camera and low to medium resolution spectrometer for wavelengths in the range 55-210 µm. It employs four detector arrays, two bolometer arrays and two Ge:Ga photoconductor arrays. The bolometer arrays are dedicated for wideband photometry, while the photoconductor arrays are to be employed exclusively for spectroscopy with a resolution of a few thousand. PACS can be operated either as an imaging photometer, or as an integral field line spectrometer.

• PACS factsheet (PDF 325kb)
• The Photodetector Array Camera and Spectrometer (PACS) for the Herschel Space Observatory presentation (pdf 5.7Mb) from SPIE June 2008, Marseille, France, and a preprint of the paper (pdf 3.2Mb), published in Proc SPIE 7010

SPIRE is a camera and low to medium resolution spectrometer complementing PACS for wavelengths in the range 194-672 µm. It comprises an imaging photometer and a Fourier Transform Spectrometer (FTS), both of which use bolometer detector arrays. There are a total of five arrays, three dedicated for photometry and two for spectroscopy.

• SPIRE factsheet (PDF 2.1Mb)
• Herschel-SPIRE: Design, Ground Test Results, and Predicted Performance presentation (pdf 3.0Mb) from SPIE June 2008, Marseille, France, and a preprint of the paper (pdf 0.64Mb) published in Proc SPIE 7010

HIFI is a very high resolution heterodyne spectrometer covering the 490-1250 GHz and 1410-1910 GHz bands. It utilises low noise detection using superconductor-insulator-superconductor (SIS) and hot electron bolometer (HEB) mixers, together with acousto-optical and autocorrelation spectrometers. HIFI is not an imaging instrument, it observes a single pixel on the sky at a time.

• HIFI factsheet (PDF 321kb)
• The Herschel Heterodyne Instrument for the Far Infrared (HIFI): Instrument and Pre-launch Testing presentation (pdf 3.8Mb) from SPIE June 2008, Marseille, France, and a preprint of the paper (pdf 1.3Mb) published in Proc SPIE 7010

Detailed information is available describing the use of the Herschel observatory and its instruments in the form observers' manuals, observing planning tools, and presentations provided in various workshops.

• The Herschel observing manuals are available under the 'Herschel Observing' Documentation. These manuals provide very detailed information in the form of observers' manuals for Herschel as an observatory, its three instruments, and the SPIRE/PACS parallel mode.
• The Herschel observing planning tool - HSpot - and its User guide are available from the 'Herschel Observing' Tools page.
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• Material presented in the Herschel observation planning workshop held at ESAC on 20-21 September 2007 and the Herschel Open Time Key Program Workshop held in ESTEC on 20-21 February 2007, can also be helpful but it must be remembered that this material represents that status at the time.

See Useful links