Herschel Space Observatory - Instrumentation

Instrumentation

The mission involves the first space observatory to cover the full far infrared and submillimetre waveband. At 3.5 meters wide, its telescope incorporates the largest mirror (made not from glass but from sintered silicon carbide) ever deployed in space. The mirror was ground and polished by Opteon Ltd. in Tuorla Observatory, Finland. The light is focused onto three instruments with detectors kept at temperatures below 2 K (−271 °C). The instruments are cooled with liquid helium, boiling away in a near vacuum at a temperature of approximately 1.4 K (−272 °C). The 2,000-litre supply of helium on board the spacecraft will limit its operational lifetime; nonetheless, it is expected to be operational for at least 3 years.

Herschel carries three detectors:

PACS (Photodetecting Array Camera and Spectrometer)

An imaging camera and low-resolution spectrometer covering wavelengths from 55 to 210 micrometres. The spectrometer has a spectral resolution between R=1000 and R=5000 and is able to detect signals as weak as −63 dB. It operates as an integral field spectrograph, combining spatial and spectral resolution. The imaging camera can image simultaneously in two bands (either 60–85/85–130 micrometres and 130–210 micrometres) with a detection limit of a few millijanskys.

SPIRE (Spectral and Photometric Imaging Receiver)

An imaging camera and low-resolution spectrometer covering 194 to 672 micrometre wavelength. The spectrometer has a resolution between R=40 and R=1000 at a wavelength of 250 micrometres and is able to image point sources with brightnesses around 100 millijanskys (mJy) and extended sources with brightnesses of around 500 mJy. The imaging camera has three bands, centered at 250, 350 and 500 micrometres, each with 139, 88 and 43 pixels respectively. It should be able to detect point sources with brightness above 2 mJy and between 4 and 9 mJy for extended sources. A prototype of the SPIRE imaging camera flew on the BLAST high-altitude balloon. NASA's Jet Propulsion Laboratory in Pasadena, Calif., developed and built the "spider web" bolometers for this instrument, which is 40 times more sensitive than previous versions. The Herschel-SPIRE instrument was built by an international consortium comprising more than 18 institutes from eight countries, of which Cardiff University was the lead institute.

HIFI (Heterodyne Instrument for the Far Infrared)

A heterodyne detector which is able to electronically separate radiation of different wavelengths, giving a spectral resolution as high as R=107. The spectrometer can be operated within two wavelength bands, from 157 to 212 micrometres and from 240 to 625 micrometres. SRON Netherlands Institute for Space Research has led the entire process of designing, constructing and testing HIFI. The HIFI Instrument Control Center, also under the leadership of SRON, is responsible for obtaining and analysing the data.

NASA developed and built the mixers, local oscillator chains and power amplifiers for this instrument.