Satellite

The Herschel satellite was about 7 metres high and 4.3 metres wide, and had a launch mass of about 3.25 tons. The industrial partnership who build the spacecraft was headed by Alcatel in Cannes, France and included Astrium in Friedrichshafen, Germany, and Thales Alenia Space in Turin, Italy.

The Herschel and Planck satellites were developed together under a common engineering project. They were both placed in orbit in one launch in 2009, using an Ariane 5 launcher. Herschel’s transfer to the L2 Lagrange point lasted approximately 4 months. The mission was planned to last at least 3 years.

Credit ESA / AOES Medialab ; background : Hubble Space Telescope, NASA/ ESA/ STScI

Herschel’s operating wavelengths range from 60 µm to 670 µm, performing both spectroscopy and photometry.
On-board equipment includes:

A Ritchey-Chrétien telescope with a 3.5 m primary mirror, cooled to about 80 K, to detect far-infrared and sub-millimetre wavelengths. The telescope was built for ESA by Astrium.
A service module, which contains the supports systems (power supply, attitude control, communications) as well as the instruments’ electronics.
A superfluid helium cryostat (at 2 K), based on technology previously used successfully on the ISO mission, containing the cold components of the three instruments:

PACS (Photoconductor Array Camera and Spectrometer) made up of an imaging photometer with two spider web bolometer arrays cooled to 300 mK (60 to 130 µm for blue and 130 to 210 µm for red) as well as a spectrometer comprising two Ge/Ga photoconductor arrays for 57 to 210 µm wavelengths.
SPIRE (Spectral and Photometric Imaging REcevier) also contains two elements: an imaging photometer observing three bands simultaneously at 250 µm (three 32x32, 300 mK bolometer arrays), 350 µm (242 mK), and 500 µm (162 mK) covering a 4x4’ field of view; and a mid-resolution (between 10 and 1,000) Fourier transform spectrometer detecting wavelengths ranging from 200 to 300 µm at 162 mK and from 300 to 670 µm at 122 mK using two 300 mK spider web bolometer arrays covering a 2x2’ field of view.
HIFI (Heterodyne Instrument for Far-Infrared) includes 5 dual-polarity SIS mixers, operating in a 480-1250 GHz frequency band, two single-polarity HEB mixers operating in a 1410-1910 GHz frequency band, and 1 acousto-optical spectrometer (AOS) as well as parallel auto-correlation spectrometers on 4 GHz.