Astronomical observations that are made by Earth-based telescopes are limited by the atmosphere, which distorts images and attenuates portions of the electromagnetic spectrum. The ionosphere reflects long-wavelength emissions in the radio spectrum back into space, thus preventing them from reaching Earth-based detectors. Water in the atmosphere absorbs infrared radiation, clouds block visible light, and the upper atmosphere - particularly the ozone layer - absorbs most of the wavelengths that are shorter (more energetic) than visible light. In addition to the atmosphere, light and radio "pollution" from natural and manmade sources also interfere with observations. Because of these factors, virtually no segment of the electromagnetic spectrum is totally free from distortion or interference, and astronomical observations that are made at the Earth's surface are correspondingly limited.
Some of the undesirable atmospheric effects may be overcome by the use of distortion-correcting optics or by placing telescopes on aircraft or mountain-top locations that are above a significant portion of the Earth's atmosphere. Even with these improvements, however, there is still much to be gained by removing all the effects of Earth's atmosphere and light and radio pollution.
Was this article helpful?