Japanese infrared space observatory goes into orbit
BY STEPHEN CLARK
Posted: February 21, 2006
The ASTRO-F observatory lifted off at 2128 GMT (6:28 a.m. local time Wednesday). The spacecraft was flown into orbit using a three-stage solid-fueled M-5 rocket that launched from the Uchinoura Space Center near Kagoshima, Japan, on the southern tip of Kyushu Island.
The 2,100-pound, twelve-foot tall satellite was deployed from the third stage of the M-5 booster just eight-and-a-half minutes after its speedy pre-dawn blastoff. Early indications are that the craft was placed in the planned initial 98-degree inclination Sun-synchronous orbit around Earth with a maximum altitude of about 455 miles and a low point of 189 miles. ASTRO-F will later use an apogee kick motor to circularize its orbit.
Renamed "Akari" after its on-orbit delivery, the ASTRO-F observatory will spend an anticipated one-and-a-half years performing an all-sky survey at infrared wavelengths. Akari, which means "light," will attempt to build upon work done by the Infrared Astronomical Satellite over 20 years ago.
That mission - led by the United States, United Kingdom, and the Netherlands - carried out the first comprehensive infrared survey, allowing scientists to create a group of detailed atlases including many of the targets detected by IRAS.
ASTRO-F will attempt to improve upon the results obtained by IRAS by at least one order of magnitude, and officials expect an upgrade in resolution will also paint a better picture of the Universe for astronomers.
Plans are to split the ASTRO-F mission into three distinct phases after the two-month checkout period is completed. The first phase will concentrate on accomplishing the all-sky survey during the first six months of the operations. Following will be another ten months of primarily targeted pointing observations of specific areas of interest as determined by a team of scientists from around the world.
The lifetime of the prime mission is determined by the availability of liquid helium stored in a cryostat aboard the satellite. The nearly 45 gallons of cryogenics are necessary to chill the 27-inch aperture telescope and science instruments to near absolute zero at six degrees Kelvin (-450 degrees Fahrenheit). Calculations show the helium will last for around 550 days before being exhausted.
The super-cold temperatures are needed to increase the sensitivity of the observatory's instruments to detect miniscule disparities in light emissions across the sky. Mechanical coolers are also carried aboard ASTRO-F to continue limited observations using the near-infrared camera for up to five years.
ASTRO-F will also look through thick veils of cosmic dust that hide newborn stars from Earth-based telescopes that rely on visible wavelengths. The study of elusive brown dwarf stars are also on the laundry list of scientific aims for the mission. Such objects are not massive enough to begin fusion to be officially classified as a true star, and ASTRO-F scientists hope to be able to pin down accurate masses and numbers for brown dwarves in our galaxy.
Another goal of the mission is to find forming extra-solar planetary systems by detecting infrared radiation from dust disks surrounding stars within 1,000 light years of Earth. Also, up to 50 new comets will be detected by ASTRO-F, scientists say.
Two additional secondary payloads were also trucked into space by the M-5 rocket. However, the outcome was not immediately announced for either project.
A tiny CubeSat known as CUTE-1.7 is supposed to work in orbit for several months before being manually disposed. The diminutive eight-pound satellite carries amateur radio equipment, and is being used as a training tool for students at the Tokyo Institute of Technology.
CUTE-1.7 utilizes a handheld personal digital assistant as the principal on-board computer, and carries three small magnetic torque devices for three-axis attitude control. At the end of its mission, the nanosatellite will deploy a 300-foot electrically charged tether to for a de-orbit test.
Another apparatus catching a ride to space aboard the M-5 rocket was a deployment test mechanism containing a solar sail made of aluminized polymer film that was supposed to deploy a maximum diameter of around 35 feet beginning just over eighteen minutes after liftoff. Two cameras positioned near the device would capture images of the critical unfurling of the solar sail for downlink to the ground. The experiment is a follow-up to a sub-orbital test conducted in 2004.
The launch was the second successful orbital mission for Japan in four days after Saturday's flight of the larger H-2A rocket that carried the multi-purpose MTSAT-2 satellite into space. Three out of five space launches thus far in 2006 have originated from Japan.