Detecting high energy radiation

• In operation
• Launched 17 October 2002
• Due to end 31 December 2012

INTEGRAL is the most sensitive gamma ray observatory ever launched and continues to change the way astronomers think of the cosmos. It is the first space observatory that can see visible light, X-rays and gamma rays at the same time.

Gamma rays are even more energetic than X-rays and much more penetrating. Fortunately, the Earth's atmosphere acts as a shield to protect us from any harmful effects of gamma rays. The downside of this is that we can only see them from space.

Gamma rays can also appear as brief explosions of radiation, known as gamma ray bursts. These short bursts create vast amounts of radiation but at the moment scientists don't know what is exploding. INTEGRAL and NASA’s Swift mission are helping us to understand these phenomena.

Thanks to INTEGRAL, we now know that more than 400 objects in space emit detectable gamma rays. After more than five years in space, INTEGRAL’s other achievements include the discovery of more than 100 ‘super-massive’ black holes and stars so deeply enveloped in dust and gas that other telescopes cannot see them. With more than 70% of the sky now observed by the spacecraft, astronomers have been able to construct a catalogue of celestial gamma ray sources.

Mission facts

• INTEGRAL employs much of the same spacecraft engineering as ESA's X-ray satellite XMM-Newton. This meant considerable amounts of money were saved in building the satellite.
  
  
• The satellite orbits Earth once every 72 hours. It spends most of its orbit at least 40,000 kms outside Earth's radiation belts. This reduces interference from background radiation.
  
  
• In November 2007, because the mission has been so successful, ESA’s Science Programme Committee unanimously approved an extension of the mission from 2010 to 2012.

Technology

Gamma rays from distant objects are relatively rare and difficult to observe. With their penetrating power they cannot be focused by conventional mirrors or lenses so special detectors and imaging systems had to be designed.

The four scientific instruments in INTEGRAL’s payload weigh a massive 2,000 kg. Two instruments are designed to both create images and measure the energy of gamma rays. Two other instruments provide simultaneous imaging of the same sky region in X-rays and optical light.

UK involvement

Researchers at the University of Southampton were among those who originally proposed the mission. They are also leading the compilation of the celestial gamma ray catalogue.