Space policy：Mercy mission
(The Economist Nov 2nd, 2006)
On October 31st America’s National Aeronautics and Space Administration (NASA) announced that it would further expand man’s knowledge of the universe by allowing astronomers to repair and upgrade the telescope that is named after him.
Since its launch in 1990 the Hubble space telescope has captured beautiful images of the universe. In its 16 years of operation it has found the first convincing evidence for the existence of black holes, made observations supporting the theory that the universe’s expansion is accelerating and confirmed that dark matter exists.
But the telescope is deteriorating. It has been in space for a long time. Dust and radiation are damaging its instruments. Without new batteries and new gyroscopes it would lose both the power and the ability to point in the right direction. It needs a service to extend its working life beyond the next two or three years.
A planned servicing mission was cancelled in January 2004 after the space shuttle Columbia was lost along with its crew of seven astronauts in 2003.
Now the administration has had a change of heart. Part of the reason is that it turned out to be impossible to put together the alternative—a robotic mission to repair Hubble—before the telescope started to crumble. So officials re-examined the possibility of a manned mission.
The mission offers the opportunity not only to repair the telescope but also to upgrade it. It will get a protective blanket and two new instruments are to be fitted. A “ cosmic origins spectrograph” will examine the structure and composition of the matter concentrated in the “cosmic web”. To do this, it will examine what happens to the beams coming from faint, distant quasars as they pass through the cosmic web. Absorption of this light should reveal the composition and specific location in space of the constituents of the cosmic web, illuminating both the large-scale structure of the universe and the progressive changes in chemical composition of matter as the universe has grown older.
A second instrument, a new wide-field camera, will extend Hubble’s capability to see deep into the universe. Using it, astronomers will observe young, hot stars that glow predominantly in the ultraviolet part of the spectrum. They will also be able to see the first stars and galaxies. These wonders can be seen only from space because water in the Earth’s atmosphere absorbs light at these wavelengths.
The proposed upgrades should keep Hubble going until 2012. Its replacement, the proposed James Webb space telescope, is supposed to be launched the following year. There would be no way to repair and upgrade this telescope, though—it would be placed in an inaccessible orbit around the so-called second Lagrangian point, where the Earth, the sun and the moon orbit one another while remaining in the same position relative to each other.
