ESA joins forces with Japan on new infrared sky surveyor

A high-capability new infrared satellite, ASTRO-F, was successfully launched last night by the Japan Aerospace Exploration Agency (JAXA). In a collaborative effort involving ESA and scientists across Europe, the spacecraft is now being prepared to start its mapping of the cosmos.

Orbiting the Earth, ASTRO-F (to be renamed Akari (light) now that it is in orbit) will make an unprecedented study of the sky in infrared light, to reveal the distant phenomena hidden from our eyes that tell the story of the formation and evolution processes taking place in the universe.

Prof. David Southwood, ESA’s Director of Science, said: “The successful launch of ASTRO-F(Akari) is a big step. A decade ago, our Infrared Space Observatory (ISO) opened up this field of astronomy, and the Japanese took part then. It is wonderful to be cooperating again with Japan in this discipline.”

“Our involvement with the Japanese in this programme responds to our long-term commitment in infrared astronomy, whose potential for discovery is huge. We are now off and rolling with ASTRO-F/Akari, but we are also working extremely hard towards the launch of the next-generation infrared telescope, ESA’s Herschel spacecraft, which will go up in the next two years,” he continued.

“This will still not be the end of the story. Infrared astronomy is also a fundamental part of the future vision for ESA’s space research, as outlined in the ‘Cosmic Vision 2015-2025’ programme. The truth is, subjects such as the formation of stars and exoplanets, or the evolution of the early universe, are themes at the very core of our programme.”

The mission

On 21 February, at 22:28 Central European Time, (22 February, 06:28 local time), a Japanese M-V rocket blasted off from the Uchinoura Space Centre, in the Kagoshima district of Japan, carrying the new infrared satellite into space.

In about two weeks’ time, ASTRO-F will be in polar orbit around the Earth at an altitude of 745 kilometres. From there, after two months of system check-outs and performance verification, it will survey the whole sky in about half a year, with much better sensitivity, spatial resolution and wider wavelength coverage than its only infrared surveyor predecessor, the Anglo-Dutch-US IRAS satellite (1983).

The all-sky survey will be followed by a ten-month phase during which thousands of selected astronomical targets will be observed in detail. This will enable scientists to look at these individual objects for a longer time, and thus with increased sensitivity, to conduct their spectral analysis.

This second phase will end with the depletion of the liquid helium needed to cool down the spacecraft telescope and its instruments to only a few degrees above absolute zero. ASTRO-F will then start its third operations phase and continue to make observations of selected celestial targets with its infrared camera only, in a few specific infrared wavelengths.

ESA’s involvement

Only two decades have passed since the birth of space-based infrared astronomy; since then, each decade has been marked by the launch of innovative infrared satellites that have revolutionised our very perception of the cosmos.

In fact, infrared satellites make possible the detection of cool objects, including planetary systems, interstellar dust and gas, or distant galaxies, all of which are most difficult to study in the visible part of the light spectrum. With infrared astronomy, it is also possible to study the birth of stars and galaxies, the ‘creation’ energy of which peaks in the infrared range.

The European Space Agency and Europe have a strong tradition in infrared astronomy, which is now being continued by the participation of the UK, the Netherlands and ESA in ASTRO-F. ESA is providing network support through its ground station in Kiruna (Sweden) for a few passes per day.

ESA is also providing expertise and support for the sky-survey data processing. This includes ‘pointing reconstruction’ – which means measuring exactly where the observed objects are in the sky, to help accelerate the production of sky catalogues and ultimately produce a census of the infrared universe.

In return, ESA has obtained ten percent of the observing opportunities during the second and third operational phases of the ASTRO-F mission, which is being allocated to European astronomers to perform their proposed observations.

“The cooperation offered to ESA by Japan in ASTRO-F will help keep up momentum for European astronomers as they build on their past work with ISO, and look forward to the launch of ESA’s Herschel infrared mission, in early 2008,” commented Prof. Southwood.

With the largest and most powerful space telescope to date (3.5 metres in diameter), Herschel will build on the ASTRO-F census of the infrared universe and on the legacy left by other satellites such as ESA’s ISO and NASA’s Spitzer. It will reveal the deepest secrets of galaxies and of star formation and evolution, while also studying the chemistry of the cold, hidden cosmos.