Artist's view of Integral

Gamma rays are even more powerful than the X-rays used in medical and dental examinations. Fortunately, the Earth's atmosphere protects us from this dangerous cosmic radiation. However, this also means that gamma rays from deep space can only be detected by satellites.

Integral is a truly international mission with the participation of various ESA member states plus the United States, Russia, the Czech Republic and Poland. The four instruments are exploited by teams led by scientists in Italy, France, Germany, Denmark and Spain. A Russian Proton rocket placed the spacecraft into orbit, while ESA and NASA ground stations stay in touch from Earth.

The Mission Operations Centre (MOC) is located at ESOC, Darmstadt, Germany; the Science Operations Centre (SOC) at ESAC in Spain; and Switzerland hosts the Integral Science Data Centre (ISDC).

	Launch of Integral on 17 Oct 2002 from Baikonur onboard a Proton launcher

The satellite was placed in a 66-hour high elliptical orbit with an apogee of 153 000 km, a perigee of 690 km, and an inclination of 51.6°. The satellite was acquired, as planned, 1 hour and 32 minutes after lift-off from ESA's Villafranca station and 3 minutes later from the Redu station.

Launch and Early Operations Phase - LEOP

LEOP included raising the orbit perigee from 690 to 9000 km and lasted, as planned, for six orbits. It involved five perigee-raising propulsion burns at apogee 3, 4, and 5, and an apogee adjustment manoeuvre at perigee 6 to adjust the geo-synchronicity of the orbit to 72 hours. During the LEOP, the instruments were switched on and checked out.

Commissioning Phase

The commissioning phase of the mission started on 4 November 2002 and lasted until 17 December when the mission entered officially its routine phase. During commissioning, calibration of the spacecraft platform took place, the main instrument's high-voltage power was switched on, and scientists and principal investigators (PIs) at the MOC measured initial instrument performance before moving to the ISDC to assist with in-flight calibration of the instruments.

Routine science operations began, as planned, at the end of 2002. The performance of the ground and space segments continues to be excellent, and exceed the original mission specifications.

Extended Mission

Integral is now in the second mission extension, and the currently planned end of mission is December 2012. The long mission duration is possible because all elements of flight hardware and software are still operating nominally - all consumables, such as fuel, etc., still have ample reserves. The continuing excellent performance and minimal degradation of the payload instruments make mission extensions highly worthwhile in terms of science return.

During this phase, Integral will face a number of challenges. In particular, the orbit is evolving such that the perigee altitude is decreasing. This change in orbit means that Integral will pass through the inner (proton) Van Allen belts every three days; it is not known how Integral will cope with such a harsh environment.

	Redu facilities

	DSN antenna at NASA Goldstone, California

Goldstone is operated by NASA's Jet Propulsion Laboratory (JPL) and its antennas have also been used as radio telescopes for scientific studies focused on mapping quasars and other celestial radio sources; the radar mapping of planets, the Moon, comets and asteroids; and spotting comets and asteroids.

This mission uses SCOS-2000

The MOC at ESOC is responsible for the operation of the spacecraft and instruments, for ensuring the spacecraft safety and health, for the maintenance of the satellite's on-board software, for the provision of flight dynamics support including determination and control of the satellite's orbit and attitude and for provision of all telemetry and auxiliary data to the ISDC.
 
 

	Integral ground segment diagram

Integral operations are executed using an automated timeline. The timeline is generated on a revolution-by-revolution basis, i.e. one timeline covers the period from perigee passage to the next perigee passage, which is approximately three days.

The MOC maintains the on-board software and the operational database and is responsible for the short- and long-term archiving of the telemetry, telecommands and auxiliary data. The archive is consolidated (filling of data gaps) with the satellite playback telemetry received from the ground stations when required. In addition to the real-time link to the ISDC that provides the majority of the TM data within seconds, the consolidated data are put on CDs and provided offline to ensure data completeness.

The main payload consists of the Spectrometer on Integral (SPI) and Imager on board Integral (IBIS).

These are complemented by two monitor instruments in the X-ray (JEM-X) and optical ranges (OMC), co-aligned with the main instruments, and a radiation monitor for real-time measurement of the radiation environment and safeguarding of the instruments.
 
 

The payload, designed and built by European scientific institutes, provides the science community with an unprecedented combination of imaging and fine spectroscopy over a very wide range of wavelengths from gamma ray to optical.
 
 
Last update: 8 January 2010