mountain profile Institute for Astronomy University of Hawaii

Despite a Difficult Start, the Akari Spacecraft Did Accomplish Its Mission

The Akari Infrared Space Telescope got off to a rocky start, but because of the hard work of astronomers and engineers, it was able to complete its main mission, an all-sky infrared survey. According to Dr. Tomotsugu Goto, a research fellow at IfA who worked on Akari (“light” in Japanese), it also helped rewrite the history of star formation throughout the cosmos.

“Nothing but troubles” is how Goto describes the beginning of the Akari mission, a joint venture of the Japanese Aerospace Exploration Agency and the European Space Agency. “The main mirror cracked during a vibration test, delaying the launch by a year. One of the detectors lost its sensitivity soon after we sealed the instrument.”

“I was at an antenna station in Chile to track the launch in 2006. Forty-five minutes after launch, I was excited to find the satellite in the expected orbit. Soon after, however, we lost the solar sensor, which delayed the start of the observations by three weeks, costing us four months of the precious liquid helium needed to keep the instruments sufficiently cool.”

Then there were problems with the data. “When I first looked at the far-infrared data from the satellite, it was all noise. After I removed the expected noise, there remained unexpected noise.” Thus began the hard work of the data reduction team, which included Goto, to separate the meaningful data from the electronic noise.

Despite all these troubles, Akari was able to finish its most important mission, the all-sky survey. The Akari All-Sky Catalogues, publicly released in March, are 3 to10 times more detailed and cover many more wavelengths (9 to160 millionths of a meter) than the catalogs of the Infrared Astronomical Satellite (IRAS), which surveyed the skies in the 1980s. According to Goto, “Akari’s catalogs will be a basis of infrared astronomy for decades to come.”

But there is more. A research team led by Goto used Akari’s data to discover the history of star formation in much more detail than was previously known. Infrared radiation can reveal star formation that is hidden by dust at visible wavelengths. Goto’s team found that the density of star formation throughout the cosmos was 20 times higher 10.6 billion years ago than it is now.

Akari is now dying. It has consumed all its liquid helium. Its detectors are losing sensitivity daily. “But at least Akari is dying after accomplishing its goal," said Goto. “I am delighted that the hard work by hundreds of astronomers and engineers has finally been rewarded.”

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