INTEGRAL (INTErnational Gamma Ray Astrophysics Laboratory) is a European (ESA) astrophysics satellite that was launched from Baikonur by a Proton-K rocket at 04:41 UT on 2002 October 17. The orbit of INTEGRAL has a very high apogee to escape magnetospheric radiation. The initial orbital parameters are period 66 hr, apogee 153,000 km, perigee 639 km, and inclination 51.7 deg.
The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) is a European Space Agency (ESA) mission designed to study celestial gamma-ray sources in the 15 keV to 10 MeV energy range. The primary INTEGRAL science payload consists of a gamma ray spectrometer (SPI) operating over 20 keV-8 MeV, a gamma ray imager (IBIS) operating over 15 keV-10 MeV, an X-ray monitor (JEM-X) operating in the 3-35 keV band, and an Optical Monitoring Camera (OMC) operating at 550 nm.
The spacecraft was launched on October 17, 2002 into a 66 hr., 639 x 153,000 km orbit at 51.7 degrees inclination. The mission is scheduled to last 2 years, and up to 5 years is possible. The spacecraft is three-axis stabilized with an absolute pointing error of 5 (y,z) to 15 (x) arcmin and an absolute measurement error of 1 (y,z) to 3 (x) arcmin. The spacecraft with solar panels stowed is roughly 3 x 4 x 5 m in size with a mass of about 4000 kg, 520 kg of that being hydrazine fuel. Science telemetry will be transmitted in S-band at 86 kbit/s to ground stations in Redu (Belgium) and Goldstone (US).
The four-ton (with fuel) cylindrical (5 m height and 3.7 m diameter) satellite is equipped with two tons of instruments to monitor gamma rays, x-rays, and visible light--the gamma ray emitters being of primary interest.
SPI (SPectrometer on Integral) is 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 is unique to each direction of arrival. Behind this plate at 1.7 m is an array of 19 cryogenic (85 deg K) germanium detectors of total area 500 cm2, to provide the energy of the incoming photons in the range 20 keV-8 MeV at an accuracy of 0.2% of their energies. A source can be located at an accuracy of 2 deg within the field of view of 16 deg. It is a massive, 1.3-ton instrument with most of the mass intended to shield away entry of stray radiation. J.-P. Roques of CSER, Toulouse, France and V. Schoenfelder of MPE, Garching, Germany are the Principal Investigators.
IBIS is a gamma ray imaging telescope to provide images in the composite energy range of 15 keV-10 MeV. It consists of a coded mask front-plate backed up by two layers of pixels. The first layer has 16,384 Cd-Te pixels; immediately behind this is a thicker layer of 4,096 Cs-I pixels to monitor the more energetic photons. It rejects stray contaminations by heavy shielding on the sides and bottom. The image resolution is 30 arc-seconds. (PIs: P. Ubertini, IAS, Rome, Italy; F. Lebrun, CE-Saclay, France; and G. DiCocco, ITESRE, Bologna, Italy.)
JEM-X (Joint European Monitor, X-rays) provides images in the 3-35 keV energy range, at a resolution of three arc-min. This too has a coded mask front-plate backed up at 3.2 m by a detection plane. The detector is 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. (PI: Niels Lund, DSRI, Copenhagen, Denmark.)
OMC (Optical Monitoring Camera) is intended to image the gamma ray sources in visible light from sources with a magnitude as weak as 19.7. It is a refractor telescope with a 5-cm lens, imaging onto an array of CCDs kept at -80 deg C. The field of view is 5 deg x 5 deg and the resolution is 18 arc-seconds. (PI: M. Mas-Hesse, LAEFF-INTA, Madrid, Spain)
Alternate Names
International Gamma-Ray Astrophysics Laboratory
Facts in Brief
Launch Date: 2002-10-17
Launch Vehicle: Proton-K
Launch Site: Tyuratam (Baikonur Cosmodrome), Kazakhstan
Mass: 3500.0 kg
Nominal Power: 690.0 W