An ESA spacecraft launched 2009 May carrying a 3.5-m telescope for imaging and spectroscopy at far-infrared and submillimetre wavelengths, from 55 to 672 μm, a part of the spectrum not previously covered. It is stationed at the L2 Lagrangian point, 1.5 million km from Earth in the direction away from the Sun. It carries three instruments: HIFI (Heterodyne Instrument for the Far Infrared), a very-high-resolution heterodyne spectrometer; PACS (Photodetector Array Camera and Spectrometer), an imaging photometer and medium-resolution grating spectrometer; and SPIRE (Spectral and Photometric Imaging Receiver), an imaging photometer and an imaging Fourier transform spectrometer. HSO is named after W. Herschel, the discoverer of infrared light, and his sister and co-worker Caroline. HSO was launched on the same rocket as Planck, another ESA scientific mission, but the two separated once in space and operate independently.
http://sci.esa.int/herschel ESA mission website.
Subjects: Astronomy and Astrophysics.