Akari (satellite)
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| Name | Akari |
| Mission type | Infrared astronomy |
| Operator | Japan Aerospace Exploration Agency |
| Spacecraft type | Infrared astronomical satellite |
| Manufacturer | Institute of Space and Astronautical Science, Mitsubishi Electric |
| Launch mass | 952 kg |
| Power | 500 W |
| Launch date | 2006-02-21 |
| Launch vehicle | M-V (rocket) |
| Launch site | Uchinoura Space Center |
| Orbit | Sun-synchronous orbit |
| Instruments | Infrared telescope, Far-Infrared Surveyor, Infrared Camera |
Akari (satellite) was a Japanese infrared astronomy satellite developed to perform an all-sky survey and pointed observations in the infrared spectrum. Funded and operated principally by the Japan Aerospace Exploration Agency and the Institute of Space and Astronautical Science, the mission combined cryogenic telescope technology, survey strategies, and international data sharing to follow on from missions such as IRAS, ISO, and contemporaneous efforts like Spitzer Space Telescope. Akari provided catalogs and maps used by researchers at institutions including NASA, European Space Agency, and universities worldwide.
Overview
Akari was designed as a dedicated infrared observatory, carrying a cooled telescope and focal-plane instruments to map the sky from near- to far-infrared wavelengths. The mission built on heritage from Infrared Astronomical Satellite (IRAS), Infrared Space Observatory (ISO), and technologies advanced by ISAS and industrial partners such as Mitsubishi Electric. Operated from a sun-synchronous polar orbit, Akari executed a full-sky survey and targeted observations to study objects ranging from solar system bodies like asteroids and comets to extragalactic targets such as starburst galaxys and active galactic nucleuses.
Mission Objectives
Primary objectives included completing an all-sky infrared survey with improved sensitivity and spatial resolution compared to IRAS, characterizing the spectral energy distributions of sources identified by Two Micron All Sky Survey and Wide-field Infrared Survey Explorer, and enabling follow-up studies by facilities like Subaru Telescope, Atacama Large Millimeter Array, and Hubble Space Telescope. Scientific goals targeted the lifecycle of interstellar medium components, the formation of protostars in molecular clouds such as Orion Nebula and Taurus Molecular Cloud, the population statistics of main belt asteroids and near-Earth objects, and the infrared properties of luminous infrared galaxys and quasars.
Spacecraft and Instruments
The Akari spacecraft carried a 68.5 cm cooled telescope and two primary instruments: the Far-Infrared Surveyor and the Infrared Camera. The Far-Infrared Surveyor provided photometric bands for studies of cold dust in regions like Perseus molecular cloud and Taurus molecular cloud, while the Infrared Camera delivered imaging and spectroscopic capabilities for targets such as protoplanetary disks and young stellar objects. Cryogenic cooling used superfluid helium, following techniques established by missions including ISO and Spitzer Space Telescope, and the payload interfaced with onboard systems developed by Institute of Space and Astronautical Science engineers and contractors from Mitsubishi Electric.
Launch and Operations
Akari was launched on 2006-02-21 by an M-V (rocket) from Uchinoura Space Center into a sun-synchronous orbit optimized for an all-sky survey. Mission operations were conducted by teams at JAXA and ISAS with scheduling for survey passes and pointed observations coordinated with observatories including Subaru Telescope, Keck Observatory, Very Large Telescope, and Green Bank Telescope for multiwavelength campaigns. After the depletion of cryogen, Akari continued limited operations in a warm phase, similar to Spitzer Space Telescope and WISE strategies, before completing its primary mission timeline.
Science Results and Discoveries
Akari delivered improved sky maps and source catalogs that refined flux measurements for millions of infrared sources, complementing databases from IRAS, 2MASS, and WISE. The mission produced new catalogs of asteroids, contributed to understanding the size distribution and albedo of main belt asteroid populations, and detected dust emission from cometary comae and Kuiper belt objects. In galactic astronomy, Akari clarified the spectral energy distributions of star-forming regions and unveiled populations of cold dense cores in molecular clouds like Perseus molecular cloud and Ophiuchus. Extragalactic results included measurements of infrared luminosities for luminous infrared galaxys and constraints on dust-obscured star formation histories in galaxy clusters and active galactic nucleus hosts.
International Collaboration and Management
The mission involved international collaborations with organizations such as NASA, European Space Agency, and research institutions across United States, United Kingdom, France, Germany, Australia, and South Korea. Data products were distributed to the scientific community via archives maintained by ISAS and partner data centers used by researchers at Harvard–Smithsonian Center for Astrophysics, Max Planck Institute for Astronomy, and national observatories. Management combined project oversight from JAXA and ISAS with scientific advisory inputs from working groups including experts affiliated with University of Tokyo, Kyoto University, and international consortia.
Legacy and Impact
Akari's all-sky infrared catalogs and maps became foundational resources for follow-up missions and surveys such as Herschel Space Observatory, ALMA, and ground-based facilities conducting multiwavelength studies. The mission advanced cryogenic telescope practice and survey methodologies used in subsequent projects, influenced target selection for programs at Subaru Telescope and Keck Observatory, and contributed to long-term datasets employed by researchers at institutions like Smithsonian Astrophysical Observatory and National Astronomical Observatory of Japan. Akari remains cited in studies of star formation, circumstellar disk evolution, and small-body populations, securing its role in the lineage from IRAS to modern infrared astronomy missions.
Category:Japanese space probes Category:Infrared telescopes Category:2006 in spaceflight