ESA Integral manoeuvres to improve future observations

Credit: ESA

ESA’s Integral observatory is able to detect gamma-ray bursts, the most energetic phenomena in the Universe.

Since 2002, ESA’s Integral spacecraft has been observing some of the most violent events in the Universe, including gamma-ray bursts and black holes.

While it still has years of life ahead, its fuel will certainly run out one day.

Integral, one of ESA’s longest-serving and most successful space observatories, has begun a series of four thruster burns carefully designed to balance its scientific life with a safe reentry in 2029.

That seems far off, but detailed planning and teamwork now will ensure that the satellite’s eventual entry into the atmosphere will meet the Agency’s guidelines for minimising space debris.

Making these disposal manoeuvres so early will also minimises fuel usage, allowing ESA to exploit the valuable satellite’s lifetime to the fullest.

This is the first time that a spacecraft’s orbit is being adjusted, after 12 years in space, to achieve a safe reentry 15 years in the future, while maximising valuable science return for the subsequent seven to eight years.

“Our four burns will use about half of the estimated 96 kg of fuel available,” says Richard Southworth, spacecraft operations manager at ESA’s Space Operations Centre, ESOC, in Darmstadt, Germany.

“This will influence how Integral’s orbit evolves, so that even after we run out of propellant we will still have a safe reentry in February 2029 as a result of natural orbit decay.

“No further manoeuvres are required between now and then and Integral can continue to operate.”

Debris Mitigation
The latest ESA debris guidelines require that a satellite must be disposed of in such a way that it poses no risk to other satellites in protected orbital regions for more than 25 years.

Although Integral’s early launch date, in 2002, means it is not required to stick to the guidelines, they were followed for planning the disposal.

“We have done a great deal of modelling for Integral’s reentry in 2029,” says Klaus Merz of ESA’s Space Debris Office.

“We’re confident that this month’s manoeuvres will put it on track for a future safe reentry at latitudes in the far south, reducing risk far below guideline levels.”

Without these firings, the fuel supply would run out in perhaps 12–16 more years, after other essentials such as power end Integral's working life, but the satellite would not reenter for up to 200 years, which would present a hazard to other missions.

ESA Integral catches dead star exploding in a Type 1a Supernova

Astronomers studying SN2014J, a Type Ia supernova discovered in January 2014, have found proof that this type of supernova is caused by a white dwarf star reigniting and exploding.

This finding was made by using ESA’s Integral observatory to detect gamma rays from the radioactive elements created during the explosion.

This sequence of artist's impressions shows some of the steps leading up to and following the explosion.

A white dwarf, a star that contain up to 1.4 times the mass of the Sun squeezed into a volume about the same size as the Earth, leeches matter from a companion star (image 1).

The Integral measurements suggest that a belt of gas from the companion star builds up around the equator of the white dwarf (image 2). 

This belt detonates (image 3) and triggers the internal explosion that becomes the supernova (image 4). 

Material from the explosion expands (image 5) and eventually becomes transparent to gamma rays (image 6).

Astronomers using ESA’s Integral gamma-ray observatory have demonstrated beyond doubt that dead stars known as white dwarfs can reignite and explode as supernovae.

The finding came after the unique signature of gamma rays from the radioactive elements created in one of these explosions was captured for the first time.

The explosions in question are known as Type Ia supernovae, long suspected to be the result of a white dwarf star blowing up because of a disruptive interaction with a companion star.

However, astronomers have lacked definitive evidence that a white dwarf was involved until now.

The ‘smoking gun’ in this case was evidence for radioactive nuclei being created by fusion during the thermonuclear explosion of the white dwarf star.

“Integral has all the capabilities to detect the signature of this fusion, but we had to wait for more than ten years for a once-in-a-lifetime opportunity to catch a nearby supernova,” says Eugene Churazov, from the Space Research Institute (IKI) in Moscow, Russia and the Max Planck Institute for Astrophysics,in Garching, Germany.

Although Type Ia supernovae are expected to occur frequently across the Universe they are rare occurrences in any one galaxy, with typical rates of one every few hundred years.

ESA INTEGRAL: reveals new facets of the Vela pulsar wind nebula

This image shows the Vela pulsar wind nebula as observed with ESA's INTEGRAL observatory (blue pixellated image) and with other high-energy astronomical facilities (coloured contours).

The INTEGRAL image shows emission detected at hard X-ray energies, between 18 and 40 keV, with the IBIS imager on board INTEGRAL, after subtraction of the point-like source corresponding to the inner nebula.

The contours show soft X-ray emission detected by the German ROSAT telescope between 0.5 and 2 keV (green) and by the Birmingham Spacelab 2 telescope between 2.5 and 12 keV (cyan), and very-high energy gamma-ray emission detected with the H.E.S.S. Telescopes above 1 TeV (magenta).

The Vela pulsar wind nebula is a cloud of highly energetic electrons and positrons that are injected by the pulsar into its surroundings and radiate across the electromagnetic spectrum. The location of the Vela pulsar is marked with a cross.

The image measures roughly two degrees on the horizontal side. North is up and East is to the left. Copyright: ESA/INTEGRAL/IBIS-ISGRI/F. Mattana et al./ROSAT/H.E.S.S. /Spacelab 2.

ESA INTEGRAL deciphers diffuse signature of cosmic-ray electrons

This image shows the entire sky at hard X-ray energies, between 50 and 100 keV, as observed with the Spectrometer on board INTEGRAL (SPI). The image is based on six years worth of data collected with this instrument.

The two main contributions to the emission at these energies are clearly visible: point sources, galactic and extragalactic alike, and diffuse emission. 

Point sources are scattered across the sky, albeit mainly concentrated along the Galactic Plane; the diffuse emission also traces the Galactic Plane and is fainter, at these energies, than the emission arising from point sources.

To study the diffuse emission in great detail and to break it down into the individual physical processes that contribute to it, astronomers need to carefully scrutinise the data and remove the contamination due to point sources. Credits: ESA/INTEGRAL/SPI.

ESA Integral: Challenges physics beyond Einstein

Integral’s IBIS instrument captured the gamma-ray burst (GRB) of 19 December 2004 that Philippe Laurent and colleagues have now analysed in detail.

It was so bright that Integral could also measure its polarisation, allowing Laurent and colleagues to look for differences in the signal from different energies.

The GRB shown here, on 25 November 2002, was the first captured using such a powerful gamma-ray camera as Integral’s. When they occur, GRBs shine as brightly as hundreds of galaxies each containing billions of stars.

Credits: ESA/SPI Team/ECF

INTEGRAL Completes The Deepest All-Sky Survey In Hard X-Rays

This image shows a map of the Galactic Bulge region, reconstructed from data collected over seven years, from 2003 to 2010, with IBIS/ISGRI on board INTEGRAL, and covering the 17-60 keV energy band. The overlaid green contours are isophotes of the 4.9 micron surface brightness of the Galaxy as seen by COBE/DIRBE, revealing the bulge/disc structure of the inner galaxy.

The near-infrared brightness of the Galaxy traces also the hard X-ray Galactic Ridge emission.