The AKARI MISSION

AKARI is a 68.5cm telescope cooled down to 6K, and will observe in the wavelength range from 1.7 (near-infrared) to 180 (far-infrared) µm.The AKARI mission is an ambitious plan to make an all-sky survey with better sensitivity, spatial resolution and wider wavelength coverage than IRAS. Besides the survey, pointed observations will also be possible. They will concentrate mainly on two high-visibility regions, the North Ecliptic Polar (NEP) region and the Large Magellanic Cloud (LMC). In addition, the so called Mission Program led by the the AKARI project team members, and Open Time Proposals will also make use of this observing mode.
AKARI is equipped with two scientific instruments, FIS & IRC.


Orbit and Observing modes

The orbit of AKARI is a Sun-synchronous polar orbit along the twilight zone. The nominal altitude is 700 km, corresponding to an orbital period of ~100 min. Observations by AKARI will be carried out either in survey mode or pointed mode.


 

In the survey mode, the satellite is operated such that the telescope scans the sky with a constant speed (3.6 arcmin/sec), spinning around the Sun-pointed axis once every orbit, and pointing the telescope towards the opposite direction to the Earth.
In the pointed mode, the telescope can point at an area of the sky for up to 10 minutes, with the total cost of 30 minutes including manoeuvre operation. Fine control of the observing position in pointed mode is possible. Observations are defined by a set of Astronomical Observation Templates. (AOT).


Mission Schedule

The mission lifetime of AKARI, expected to be 550 days, is divided into a performance verification (PV) phase and three observation phases:

  • [Phase 0 (PV Phase)] The first two months after the launch are assigned to the PV phase. In this period, the spacecraft system and the focal-plane instruments are checked out, and the initial calibration of the focal-plane instruments will be carried out.
  • [Phase 1] Approximately the first half year by which time AKARI will have scanned the entire sky is called Phase 1. In this period, the Large Area Survey Programmes, namely the All-Sky Survey and the NEP / LMC pointing surveys will be carried out with the highest priority.
  • [Phase 2] This phase will continue until all liquid Helium evaporates. Many pointed observations belonging to Mission Programmes and Open Time proposals will be performed as well as supplemental scan observations to complete the All-Sky Survey. Since Phase 2 is expected to last for 10 months, about 2/3 of the sky area will be observed at least twice in this phase.
  • [Phase 3] After the boil-off of liquid Helium, the mechanical coolers will keep the temperature low enough to observe with the IRC/NIR camera. Phase 3, where only the IRC/NIR camera is operated, will continue until any on-board instrument (NIR camera itself, mechanical cooler etc.) ceases to function.

Click here for a short overview of the AKARI mission.