NASA - National Aeronautics and Space Administration

In the Beginning
Since the dawn of civilization, man was limited by his vision and imagination about his understanding of the universe. The telescope enhanced his vision and tempered his pride, as observations by Copernicus, Galileo and Kepler in the 16th and 17th centuries A.D. rebuffed the millennia-old conceit that the Earth is the center of the universe, spearheading the Scientific Revolution.

By the 18th century, the telescope would become the indispensable instrument for investigations of the cosmos. Bigger and better telescopes were built all over the world. Planets, stars, and nebulae which could not be seen by the naked eye were now being routinely noted and logged. Advances in spectroscopy, photography, and photometry increased telescope versatility, sensitivity, and discovery power.

Enter Edwin Hubble
By the turn of the 20th century, most astronomers believed that the observable universe consisted of one galaxy, our Milky Way Galaxy, an oasis of stars, dust, and gas in the vastness of space. However, in 1924, American astronomer Edwin Hubble used the 100-inch Hooker Telescope (see image below) on Mount Wilson near Los Angeles, California, to observe billions of other galaxies besides our own Milky Way, almost all moving away from each other. This suggested that the universe is expanding, unleashing a Pandora's box of seminal inquiries—such as the Big Bang theory—about the possible beginning and end of the universe—issues which are still being debated to this day.

Image left: American astronomer Edwin Hubble in 1924 - used the 100-inch Hooker Telescope. Image credit: NASA

Astronomers like Edwin Hubble (before and after his time), toiled long, frigid nights inside enormous dome-shaped "observatories" pointing their telescopes skyward, yearning for the best possible snapshot of the heavens. However they faced a major obstacle that stood between them and a clear view of the universe: the Earth's atmosphere. The Earth's atmosphere is a fluid, chaotic soup of gas and dust. It blurs visible light, causing stars to twinkle and making it difficult to see faint stars. It hinders or even totally absorbs other wavelengths of light, making observations of such wavelength ranges as infrared, ultraviolet, gamma rays and X-rays difficult or virtually impossible (it is also these properties which protect us from the harmful effect of these rays).

Observatories with the largest of telescopes in various continents have been perched upon mountain tops and away from distracting city lights, from Caucasus Mountains in Europe to the Australian outback, with varying levels of success. Adaptive optics and other image processing techniques have minimized - but not totally eliminated - the effects of the atmosphere.

A Telescope in Space?
In 1923, German scientist Hermann Oberth, one of the three fathers of modern rocketry (Oberth, Robert Goddard and Konstantin Tsiolkovsky), published "Die Rakete zu den Planetenraumen" ("The Rocket into Planetary Space"), which mentioned how a telescope could be propelled into Earth orbit by a rocket. In 1946, Princeton astrophysicist Lyman Spitzer wrote about the scientific benefits of a telescope in space, above Earth's turbulent atmosphere.

Image right: Image of an Optical Telescope assembly drawing. Image credit: NASA

Following the launch of the Soviet satellite Sputnik in 1957, the fledgling National Aeronautics and Space Administration (NASA) successfully launched two Orbital Astronomical Observatories (OAOs) into orbit. They made a number of ultraviolet observations and provided learning experiences for the manufacture and launch of future space observatories.

The LST - Large Space Telescope
Meanwhile, scientific, governmental, and industrial groups planned the next step beyond the OAO program. Spitzer gathered the support of other astronomers for a "large orbital telescope" and addressed the concerns of its critics. In 1969, the National Academy of Sciences gave its approval for the Large Space Telescope (LST) project, and the hearings and feasibility studies continued.

After Armstrong's "giant leap for mankind" on the moon in 1969, funding for NASA space programs began to dwindle, putting the LST program in jeopardy. LST planners had to design the telescope under budget constraints. A number of downsizing measures were weighed and considered: decrease the size of the primary mirror, the number of scientific instruments, the diameter of the Systems Support Module and the number of spare parts created and tests performed. In 1974, the LST Science Working Group recommended the space telescope carry a large complement of interchangeable instruments. They would have specifications to resolve at least one-tenth of an arcsecond, and have a wavelength range from ultraviolet through visible to infrared light.

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