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STUDENT FEATURES
NASA's Great Observatories

03.11.04

cover of NASA's Great Observatories publication
NASA's Great Observatories has model plans
Why are space observatories important? The answer concerns twinkling stars in the night sky. To reach telescopes on Earth, light from distant objects has to penetrate Earth's atmosphere. Although the sky may look clear, the gases that make up our atmosphere cause problems for astronomers. These gases absorb the majority of radiation emanating from celestial bodies so that it never reaches the astronomer's telescope. Radiation that does make it to the surface is distorted by pockets of warm and cool air, causing the twinkling effect. In spite of advanced computer enhancement, the images finally seen by astronomers are incomplete.

Observatories located in space collect data free from the distortion of Earth's atmosphere. Space observatories contain advanced, highly sensitive instruments, such as telescopes (the Hubble Space Telescope and the Chandra X-ray Observatory) and detectors (the Compton Gamma Ray Observatory and Chandra X-ray Observatory), that allow scientists to study radiation from neighboring planets and galaxies billions of light years away. By analyzing the spectrum of radiation emitted or absorbed by an object, scientists can determine the temperature, chemical composition, and motion of an object. The light from these distant celestial bodies may take billions of years to reach the observatories, so scientists can actually look into the past and learn what was happening in the universe when it was young. The data that these observatories gather help scientists determine how stars and galaxies are formed and provide insights into the origin and evolution of the universe.

NASA, in conjunction with other countries' space agencies, commercial companies, and the international community, has built observatories such as the Hubble Space Telescope, the Compton Gamma Ray Observatory, and the Chandra X-ray Observatory to find the answers to numerous questions about the universe. With the capabilities the Space Shuttle provides, scientist now have the means for deploying these observatories from the Shuttle's cargo bay directly into orbit.

black and white drawing of the Hubble Space Telescope
Hubble Space Telescope
Hubble Space Telescope
NASA's Hubble Space Telescope, the first of the great observatories, was deployed from the Space Shuttle Discovery into Earth orbit in April 1990. It is a product of two decades of research and development by 10,000 scientists and engineers at various NASA Centers, private companies, universities, and the European Space Agency. The purpose of the Hubble, the most complex and sensitive optical telescope ever made, is to study the cosmos from low-Earth orbit for 15 years or more.



black and white drawing of Compton Observatory
Compton Gamma Ray Observatory
Compton Gamma Ray Observatory
The Compton Gamma Ray Observatory (CGRO) is the second of the great observatory series of four spacecraft NASA plans to launch. Launched in 1991, the CGRO is a complex spacecraft fitted with four different gamma-ray detectors, each of which concentrates on different but overlapping energy ranges. The instruments are the largest of their kind that have ever flown in space; each instrument weighs about 6 tons, and three of them are about the size of a subcompact car. Size is important because gamma rays can only be detected when they interact with matter. The bigger the masses of the detectors, the greater the number of gamma rays they can detect. (Note: The Compton Gamma Ray Observatory was de-orbited on June 4, 2000. Pieces of the observatory that survived re-entry landed in the Pacific Ocean southeast of Hawaii.)



black and white drawing of the Chandra Observatory
Chandra X-Ray Observatory
Chandra X-Ray Observatory
NASA's Chandra X-ray Observatory (CXO) is the most sophisticated x-ray observatory ever built. It observes x-rays from high-energy regions of the universe, such as hot gas in the remnants of exploded stars. This observatory has three major parts: (1) the x-ray telescope, whose mirrors will focus x-rays from celestial objects; (2) science instruments, which record the x-rays so that x-ray images can be produced and analyzed; and (3) the spacecraft, which provides the environment necessary for the telescope and the instruments to work.



Spitzer Space Telescope
The Spitzer Space Telescope (formerly SIRTF, the Space Infrared Telescope Facility) was launched into space by a Delta rocket from Cape Canaveral, Florida on 25 August 2003. During its 2.5-year mission, Spitzer will obtain images and spectra by detecting the infrared energy, or heat, radiated by objects in space between wavelengths of 3 and 180 microns (1 micron is one-millionth of a meter). Most of this infrared radiation is blocked by the Earth's atmosphere and cannot be observed from the ground.

To learn more, please visit NASA's Great Observatories.




Excerpted from http://spacelink.nasa.gov/products/NASAs.Great.Observatories.Kit/NASA.Great.Observatories.pdf and http://sirtf.caltech.edu/index.shtml
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Editor: Shelley Canright
NASA Official: Brian Dunbar
Last Updated: December 9, 2007
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