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).
|Mission type||Infrared telescope|
|Mission duration||5 years, 9 months|
|Launch mass||952 kg (2,099 lb)|
|Dimensions||5.5 m × 1.9 m × 3.2 m (18.0 ft × 6.2 ft × 10.5 ft)|
|Start of mission|
|Launch date||21:28, 21 February 2006 (UTC)|
|Rocket||M-V, mission M-V-8|
|Launch site||M-V Pad, Uchinoura Space Center|
|End of mission|
|Deactivated||24 November 2011|
|Semi-major axis||6,884 km (4,278 mi)|
|Perigee altitude||423.9 km (263.4 mi)|
|Apogee altitude||602.3 km (374.3 mi)|
|Argument of perigee||124.2012 degrees|
|Mean anomaly||354.1441 degrees|
|Mean motion||15.1995622 rev/day|
|Epoch||9 July 2015, 13:43:21 UTC|
|Diameter||0.67 m (2.2 ft)|
|Focal length||4.2 m (14 ft)|
|Wavelengths||1.7 to 180 µm (Infrared)|
|FIS: Far-Infrared Surveyor|
IRC: Infra-Red Camera
By mid-August 2006, Akari finished around 50 percent 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 percent 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 percent of the sky was scanned and more than 5,000 pointed observations were done.
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 would have continued energy supply would have been cut off.
A limited observation 'warm' programme continued with just NIR.
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.