Overview (The Solar System)
Ground-based telescopes have a long history of advancing various areas of Astronomy research. Starting in the 1960’s, large ground-based telescopes (which, for the purposes of this discussion, are those telescopes situated in advantageous locations on Earth’s surface and having apertures larger than 250 centimeters) were used to explore and further study objects in our solar system. For example, in the 1950’s, the Martian atmosphere was believed to be thin, and, based on the intensity and polarization of Martian reflected light, Martian surface pressure was determined to be only 5 to 10 percent of that on Earth. Designers of preliminary Martian landers used this value when deciding whether a descent to the Martian surface should be effected by balloon, glider, or downward-pointing rocket engine. Also, the presence of this much atmosphere suggested that Martian life might exist, as there would be enough air to breathe (if free oxygen were present) and enough protection from ultraviolet light and extreme temperature changes.
However, a University of California scientist, Hyron Spinrad, using ground-based telescopes, found evidence that the correct value might be very different. When he was able to obtain good high-dispersion spectra using the Lick Observatory’s 3-meter telescope in the early 1960’s, Spinrad concluded that the true value for the Martian surface pressure must be only about 5 millibars. This is only 0.5...
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Knowledge Gained (The Solar System)
In the past, ground-based telescopes have helped scientists learn more about our solar system. Among the most important ways are the following: gathering of basic data on planetary celestial mechanics; discovery and orbit determination of comets and asteroids; mapping of galactic X-ray and infrared sources; discovery of quasars and radio galaxies; detection of cosmic background radiation; and the search for extrasolar planets.
In order to determine the continuously changing orbits of the planets well enough to make interplanetary spaceflight possible, it is important to map planetary positions very accurately. Laser ranging of the Moon, for example, allows astronomers with large ground-based telescopes to measure its distance to within a few centimeters. Radar-ranging measurements of the planets, especially Venus, Mercury, and Mars, have led to very precise determinations of their positions.
Spacecraft exploration of comets depends on ground-based telescopes, to discover comets in the first place and then to monitor them in their somewhat unpredictable paths near the Sun and Earth. Exploration of asteroids by Spacecraft similarly depends on ground-based telescopes for tactical support.
Most of the cosmic objects found at X-ray and infrared wavelengths by orbiting detectors would be unexplained were it not possible to study them at other wavelengths from the ground. For example, two of the objects thought to be...
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Context (The Solar System)
Astronomy seeks a better understanding of cosmology. Ground-based telescopes have provided the basic list of objects and phenomena (including quasars, radio galaxies, and cosmic background radiation) that allow astronomers to penetrate to the edge of the universe and the beginning of time. New generations of ground-based telescopes are designed to push farther into deep space and to determine the true story of how the universe came about. They study distant galaxies, stars, and planetary systems to learn about the formation and evolution of our own solar system.
Despite the advent of space-based observatories, ground-based observations will continue to play a major role in astronomy so long as the risks and costs associated with space-based telescopes continue to be high. Ground-based observations will therefore continue to provide data and images complementary to space-based observations, which together will aid astronomers in understanding the nature and evolution of the physical universe.
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Further Reading (The Solar System)
Anderson, Geoff. The Telescope: Its History, Technology, and Future. Princeton, N.J.: Princeton University Press, 2007. Anderson does a good job of summarizing the history of telescopes from their earliest days to those currently under construction. Intended to give the general reader the basics behind telescope design and a notion of current advancements in the field.
Brunier, Serge, and Anne-Marie Lagrange. Great Observatories of the World. Buffalo, N.Y.: Firefly Books, 2005. A photographic tour of fifty-six of the world’s most impressive observatories. Decribes how telescopes work, as well as new advances in ground-based telescopes and the higher-resolution photographs they produce. For the general reader.
Kenyon, Ian. The Light Fantastic: A Modern Introduction to Classical and Quantum Optics. New York: Oxford University Press, 2008. An introductory work on optics aimed at advanced undergraduate and first-year graduate students. Also gives the reader practical examples and real-world applications. Includes a separate chapter on telescopes.
Kirby-Smith, Henry T. U.S. Observatories: A Directory and Travel Guide. New York: Van Nostrand Reinhold, 1976. A complete description of U.S. observatories, with some history and an account of the types of research and the equipment available. Notes on public availability for some are included. Suitable for general readers....
(The entire section is 466 words.)