This week engineers at the Japan Aerospace Exploration Agency (JAXA) ended the mission of Akari, an orbiting observatory that scanned the entire sky at far-infrared wavelengths. The shutdown command was sent on November 24th, according to a brief JAXA statement. But operations effectively ended last May, when an electrical malfunction prevented detectors and circuits from getting enough power each time the spacecraft passed through Earth’s shadow.
Not to worry, though: by then this little-known workhorse (known as Astro F during development) had long completed its intended mission. After launch in February 2006, the orbiting observatory began scanning the entire sky from 1.7 to 180 microns, using a telescope with a 26-inch (65-cm) aperture and detectors chilled by liquid helium to within 11° F (6 K) of absolute zero. JAXA got assistance from the European Space Agency, which provided tracking and data-processing support in exchange for 10% of the observing time during the latter stages of the mission.
Far- and mid-infrared observations ended when the cryogenic coolant ran out in August 2007, but by then Akari (meaning “light” in Japanese) had scanned 94% of the celestial sphere.
It was the first good look at the sky in the far infrared — a spectral region utterly invisible to telescopes on the ground — since the Infrared Astronomical Satellite had made its sweeps more than two decades earlier. Akari also probed much longer wavelengths than did its contemporary, NASA’s Wide-field Infrared Survey Explorer, which likewise ceased operations this year.
Along the way Akari provided views of more than 5,000 individual sources, and targeted observations at short infrared wavelengths continued even after 2007. For example, three years ago astronomers released dramatic new details of the shock wave created by Betelgeuse as this red supergiant plows through an interstellar flow that originates in Orion's Belt.
More recently a team led by Toshio Matsumoto (Seoul National University) found brightness fluctuations across broad swaths of sky at 2.4, 3.2, and 4.1 microns that they attribute to clustering of the first stars, which formed 300 million years after the Big Bang. Their research appears in November 1st’s Astrophysical Journal, but you’ll find a nice summary here.
Click here to check out more of the mission’s highlights.