AKARI (ASTRO-F) was an infrared astronomy satellite developed by Japan Aerospace Exploration Agency, in cooperation with institutes of Europe and Korea. It was launched on 21 February 2006, at 21:28 UTC (06:28, 22 February JST) by M-V rocket into Earth Sun-synchronous orbit. After its launch it was named AKARI (明かり), which means light in Japanese. Earlier on, the project was known as IRIS (InfraRed Imaging Surveyor). Its primary mission was to survey the entire sky in near-, mid- and far-infrared, through its 68.5 cm aperture telescope.

Technical design

Its designed lifespan, of far- and mid-infrared sensors, was 550 days, limited by its liquid helium coolant. Its telescope mirror was made of silicon carbide to save weight. The budget for the satellite was ¥13,4 billion (~US$110 million).

History

By mid-August 2006, AKARI finished around 50 per cent of the all sky survey. By early November 2006, first (phase-1) all-sky survey finished. Second (phase-2) all-sky survey started on 10 November 2006. Due to the malfunction of Sun sensor after the launch, ejection of telescope aperture lid was delayed, resulting in the coolant lifespan estimate being shortened to about 500 days from launch. However, after JAXA estimated the remaining helium during early March 2007, observation time was extended at least until 9 September. On 11 July 2007, JAXA informed that 90 per cent of the sky was scanned twice. Also around 3,500 selected targets have been observed so far. On 26 August 2007, liquid-Helium coolant depleted, which means the completion of far- and mid-infrared observation. More than 96 per cent of the sky was scanned and more than 5,000 pointed observations were done. British and Japanese project team members were awarded a Daiwa Adrian Prize in 2004, by the Daiwa Anglo-Japanese Foundation in recognition of their collaboration. During December 2007, JAXA performed orbit correction manoeuvres to bring AKARI back into its ideal orbit. This was necessary because the boiled off helium led to an increase in altitude. If this had continued, the energy supply would have been cut off.

2008–2010

A limited observation 'warm' programme continued with just NIR.

End of mission

In May 2011, AKARI suffered a major electrical failure and the batteries could not take full charge from the solar panels. As a result, its science instruments were rendered inoperable when the satellite was in the Earth's shadow. The operation of satellite was terminated officially on 24 November 2011. The satellite reentered the atmosphere on 11 April 2023 at 04:44 UTC.

Results

The AKARI All-Sky Survey Point Source Catalogues was released on 30 March 2010. Astronomy and Astrophysics, Vol. 514 (May 2010) was a feature issue of AKARI's results.