INTEGRAL (INTErnational Gamma Ray Astrophysics Laboratory) was a European (ESA) astrophysics satellite. The four-ton (with fuel) cylindrical (5 m height and 3.7 m diameter) satellite was equipped with two tons of instruments to monitor gamma rays, x-rays, and visible light--the gamma ray emitters being of primary interest.

The satellite was equipped with the following instruments:

• SPI (SPectrometer on Integral) was a gamma ray spectrometer with a "coded mask" front-plate consisting of 64 transparent and 63 opaque small hexagons arranged in a complex pattern. The shadow provided by the plate was unique to each direction of arrival. Behind this plate at 1.7 m was an array of 19 cryogenic (85° K) germanium detectors of total area 500 cm2, to measure the energy of the incoming photons in the range 20 keV-8 MeV at an accuracy of 0.2% of their energies. The instrument allowed a celestial gamma source to be located at an accuracy of 2° within the field of view of 16°. Most of the mass of the 1.3-ton instrument was intended to shield the detectors from stray radiation. J.-P. Roques of CSER, Toulouse, France and V. Schoenfelder of MPE, Garching, Germany were the Principal Investigators.

• IBIS was a gamma ray imaging telescope providing images in the composite energy range of 15 keV-10 MeV. It consisted of a coded mask front-plate backed up by two layers of pixels. The first layer had 16,384 Cd-Te pixels; immediately behind this was a thicker layer of 4,096 Cs-I pixels to monitor the more energetic photons. It rejected stray contamination by heavy shielding on the sides and bottom. The image resolution was 30 arc-seconds. (Principal Investigators: P. Ubertini, IAS, Rome, Italy; F. Lebrun, CE-Saclay, France; and G. DiCocco, ITESRE, Bologna, Italy.)

• JEM-X (Joint European Monitor, X-rays) provided images in the 3-35 keV energy range, at a resolution of three arc-min. This too had a coded mask front-plate backed with a 3.2 m by a detection plane. The detector was a pair of xenon-methane gas chambers, backed up by a 1,000-cm2 grid of position sensing wires which collect the accelerated and cascading photoelectrons. (Principal Investigator: Niels Lund, DSRI, Copenhagen, Denmark.)

• OMC (Optical Monitoring Camera) was intended to image the gamma ray sources in visible light from sources with a magnitude as weak as 19.7. It was a refractor telescope with a 5-cm lens, imaging onto an array of CCDs kept at -80° C. The field of view was 5° x 5° and the resolution was 18 arc-seconds. (Principal Investigator: M. Mas-Hesse, LAEFF-INTA, Madrid, Spain)

Associated Launch Vehicle: Proton 8K82K / 17S40.

• 2002 October 17 - Integral - Launch Site: Baikonur. Launch Vehicle: Proton. Mass: 4,100 kg (9,000 lb). Perigee: 9,283 km (5,768 mi). Apogee: 153,435 km (95,339 mi). Inclination: 53.40 deg. Period: 4,310.60 min.

  INTEGRAL (INTErnational Gamma Ray Astrophysics Laboratory) was a European (ESA) astrophysics satellite. The orbit had a very high apogee to escape magnetospheric radiation.