Editing INTEGRAL (section)

==Instruments==
Four instruments with large fields-of-view are co-aligned on this platform, to study targets across such a wide energy range of almost two orders of magnitude in energy (other astronomy instruments in X-rays or optical cover much smaller ranges of factors of a few at most).  Imaging is achieved by [[coded aperture|coded masks]] casting a shadowgram onto pixelised cameras; the tungsten masks were provided by the University of Valencia, Spain.

The INTEGRAL imager, '''IBIS''' (Imager on-Board the INTEGRAL Satellite) observes from 15 [[keV]] (hard X-rays) to 10 [[MeV]] (gamma rays).  Angular resolution is 12 arcmin, enabling a bright source to be located to better than 1 arcmin.  A 95 x 95 mask of rectangular [[tungsten]] tiles sits 3.2 meters above the detectors.  The detector system contains a forward plane of 128 x 128 Cadmium-Telluride tiles (ISGRI- Integral Soft Gamma-Ray Imager), backed by a 64 x 64 plane of Caesium-Iodide tiles (PICsIT- Pixellated Caesium-Iodide Telescope).  ISGRI is sensitive up to 1 MeV, while PICsIT extends to 10 MeV.  Both are surrounded by passive shields of tungsten and lead. IBIS was provided by PI institutes in Rome/Italy and Paris/France.

[[File:HURA_hexagonal_coded_aperture_mask_principle.svg|thumb|Simplified principle of operation of a HURA hexagonal coded aperture mask used in SPI]]
The spectrometer aboard INTEGRAL is '''SPI''', the SPectrometer of INTEGRAL. It was conceived and assembled by the French Space Agency [[CNES]], with PI institutes in Toulouse/France and Garching/Germany. It observes radiation between 20 [[keV]] and 8 [[MeV]].  SPI has a [[coded mask]] of hexagonal [[tungsten]] tiles, above a detector plane of 19 [[germanium]] crystals (also packed hexagonally).  The high energy resolution of 2 keV at 1 MeV is capable to resolve all candidate gamma-ray lines. The Ge crystals are actively cooled with a mechanical system of Stirling coolers to about 80K.

IBIS and SPI use active detectors to detect and veto charged particles that lead to background radiation.  The SPI '''ACS''' (AntiCoincidence Shield) consists of a BGO scintillator blocks surrounding the camera and aperture, detecting all charged particles, and photons exceeding an energy of about 75 keV, that would hit the instrument from directions different from the aperture.  A thin layer of plastic [[scintillator]] behind the tungsten tiles serves as additional charged-particle detector within the aperture.

The large effective area of the ACS turned out to be useful as an instrument in its own right.  Its all-sky coverage and sensitivity make it a natural [[gamma-ray burst]] detector, and a valued component of the [[InterPlanetary Network|IPN]] (InterPlanetary Network).

Dual '''JEM-X''' units provide additional information on sources at soft and hard X-rays, from 3 to 35 keV.  Aside from broadening the spectral coverage, imaging is more precise due to the shorter wavelength.  Detectors are gas scintillators ([[xenon]] plus [[methane]]) in a microstrip layout, below a mask of hexagonal tiles.

INTEGRAL includes an Optical Monitor ('''OMC''') instrument, sensitive from 500 to 580 [[nanometer|nm]]. It acts as both a framing aid, and can note the activity and state of some brighter targets, e.g. it had been useful to monitor supernova light over months from SN2014J.

The spacecraft also includes a radiation monitor, INTEGRAL Radiation Environment Monitor ('''IREM'''), to note the orbital background for calibration purposes.  IREM has an electron and a proton channel, though radiation up to [[cosmic rays]] can be sensed.  Should the background exceed a preset threshold, IREM can shut down the instruments.