Integral gamma-ray telescope mission was a brilliant success

The European Space Agency’s (ESA) International Gamma-Ray Astrophysics Laboratory (Integral) was launched on October 17, 2002 from the Baikonur Cosmodrome in Kazakhstan. Its mission was to observe the extreme and ever-changing cosmos.

“For over two decades, Integral has shown us time and time again how important it is to look at the sky in gamma-ray light,” noted Jan-Uwe Ness, ESA’s Integral Project Scientist.

“Some of the bursts of light associated with extreme physical events in our Universe can only be fully understood if we catch the rays that come from the very core of the blasts: the gamma rays.”

Integral reveals cosmic mysteries

Unlike visible and radio light, which ground-based telescopes can observe, cosmic gamma rays must be captured in space. Earth’s atmosphere acts as a shield and protects us from these harmful rays.

“Integral has transformed our understanding of the dynamic, high-energy Universe and physics in extreme conditions,” added Prof. Carole Mundell, ESA Director of Science.

“That Integral’s spacecraft and instrumentation have performed so exquisitely well for so many years is testament to the quality of the technology developed by the European scientific community and space industry at the turn of the millennium, and the science and engineering teams at ESA who have operated this mission ever since. Congratulations to all our communities for their dedication and achievements,” Mundell enthused.

Integral helped explain powerful space explosions

Integral has played a key role in solving the mysteries of gamma-ray bursts (GRBs). These energetic flashes appear in the sky about once per day, often outshining all other gamma-ray sources combined.

Scientists now know that longer GRBs, which last several seconds, result from the collapse of massive stars into supernovae. Shorter bursts happen when neutron stars or black holes collide.

“What I find impressive about Integral are its unexpected discoveries,” remarks Jan-Uwe Ness.

“It turned out that Integral was ideal for tasks not at all foreseen when the mission was conceived. An example is its ability to track down the sources in the sky that generated some of the gravitational waves and ultrahigh-energy neutrinos caught by specialised instruments on the ground.”

When Integral launched, scientists were unsure whether gravitational waves could ever be directly detected. The first confirmed observation came 13 years later, in 2015, by the LIGO detectors in the U.S.

Discoveries that shaped astronomy

Integral’s breakthroughs continued. Just in the past two years, it captured the most powerful gamma-ray burst ever observed. The blast even affected Earth’s protective ozone layer.

“This GRB took place in a galaxy almost two billion light-years away – it is mind-boggling to think that Earth can be affected by an event that took place in a remote corner of the Universe, two billion years ago,” marveled Ness.

Recent discoveries also include a rare 0.1-second magnetar outburst, which emitted as much energy as the Sun produces in half a million years. Integral also found that thermonuclear explosions power jets in a neutron star.

A pioneering observatory

At the time of its launch, Integral was the most advanced gamma-ray observatory available. It was the first space-based observatory capable of observing celestial objects in gamma rays, X-rays, and visible light simultaneously.

Three features made Integral’s discoveries possible: its large field of view, its ability to capture detailed images and spectra at high energies, and its monitoring capability with X-ray and optical cameras. These elements helped pinpoint gamma-ray sources with unprecedented precision.

The final chapter

“After 2886 orbits and 22 years gazing into the depths of our cosmos, today Integral’s sensitive instruments will stop collecting scientific data. But the legacy of ESA’s gamma-ray observatory will serve scientists for many more years to come,” concluded Matthias Ehle, Integral’s Mission Manager at ESA.

 “The wealth of data collected over two decades will be stored at the Integral Science Legacy Archive. It will be essential for future research and to inspire a new generation of astronomers and engineers to develop exciting new missions.”

The scientists adjusted Integral’s orbit in 2015 so that it would gradually move into a position to ensure a safe re-entry into Earth’s atmosphere, in early 2029. This aligns with the ESA’s commitment to reducing space debris.

During the next four years, ESA engineers will monitor the spacecraft, even though its scientific operations will have ceased.

Integral’s mission may be ending, but its impact on high-energy astrophysics will endure for generations.

Information for this article was obtained from an ESA press release.

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