THE SPIRE INSTRUMENT FOR HERSCHEL

SPIRE, the Spectral and Photometric Imaging Receiver, will be a bolometer instrument for ESA’s Herschel satellite. Its main scientific goals are deep extragalactic and galactic imaging surveys and spectroscopy of star-forming regions in own and nearby galaxies. The SPIRE detectors are feedhorn-coupled NTD “spider-web” bolometers. The instrument comprises a three-band imaging photometer covering the 250-500 µm range, and an imaging Fourier Transform Spectrometer (FTS) covering 200-670 µm. The photometer has a field of view of 4 x 8 arcminutes which is observed simultaneously at 250, 350 and 500 µm, with dichroic beam dividers separating the three spectral bands. Its angular resolution is determined by the telescope diffraction limit, with FWHM beam widths of approximately 17, 24 and 35 arcseconds at 250, 350 and 500 µm, respectively. An internal beam steering mirror can be used for spatial modulation of the telescope beam, and observations can also be made by scanning the telescope without chopping, providing better sensitivity for source confusion-limited deep surveys. The FTS has a field of view of 2.6 arcminutes and an adjustable spectral resolution of 0.04 - 2 cm �1 (λ/∆λ = 20 - 1000 at 250 µm). It