* Astronomy

The Japanese X-ray observatory Astro-E2 will blast off on Wednesday 0330 GMT onboard an M5 rocket from Uchinoura Space Centre in Kagoshima, near Japan's southern tip.



The Japanese X-ray observatory will carry the coldest instrument ever to fly in space. The instrument is designed to study some of the most energetic phenomena in the universe.
It will orbit at an altitude of 560 kilometres, studying X-rays emitted from black holes in the process of devouring hot gas, exploding stars, and clouds of gas heated to millions of degrees by other violent events.

The mission's instrumentation was originally proposed for launch on NASA's Chandra X-ray Observatory in 1999. But budget problems prevented the instruments from being included in that mission. Japan and the US next tried to launch the instruments aboard a mission called Astro-E in 2000. But the first stage of its M5 rocket failed before the satellite could reach orbit.

"It went into the drink and we were extraordinarily depressed" - Richard Mushotzky, a team member at NASA`s Goddard Space Flight Centre in Greenbelt, Maryland, US.
But the team used the delays to improve the mission, which will now launch with twice its original ability to resolve X-ray energies.

It will do accomplish this using a different approach from the two main X-ray telescopes already in space, Chandra and Europe's XMM-Newton. These study incoming X-ray light by effectively splitting it through a prism. Astro-E2 will instead measure how much a detector's temperature changes every time a photon hits it.
This sensitive task requires Astro-E2`s main instrument, the X-Ray Spectrometer (XRS), to be cooled to just 0.06 degrees above absolute zero. This will allow it to detect extremely small changes in photon energies - representing a 10-fold improvement in sensitivity compared to existing detectors.

"It`s interesting that we have to fly this thing so cold to look at things that are so hot" - Richard Mushotzky.

To keep the device cold, three layers insulate it from the relative warmth of space, which is 2.7 degrees above absolute zero (2.7 Kelvin). Liquid helium at 1.3 K provides the innermost layer around the refrigerator holding the XRS. A layer of solid neon at 10 K blankets that, followed by a layer of insulation that wraps around the entire setup like a thermos.

This insulation is expected to keep the XRS cold enough to function for two to three years. But the mission's other instruments - including four CCD cameras and a high-energy X-ray detector - will continue to measure X-ray energies for at least a further two years.

Astro-E2 launch is scheduled for 12:30 pm JST (Japan Standard Time) on July 6, 2005 (0330 GMT). As of 7 pm JST on July 5, they are go for launch, although the weather is currently not favourable.
Launch window extends from July 6 through July 15, and again from July 22 through August 2.