Sorry this is up a bit late, I've been working on writing and lost track of time.
Eyes turned Skyward, Post #19
Magazine advertisement, background is a composite of image of girl on-stage in school play in upper left fading into the “Pillars of Creation” on the lower right, with following text:
(Upper left) Whether it's the birth of a star...
(Lower right) or the birth of a star...
(Lower center)Kodak is there
(Sample ad copy from Kodak's "Universal" campaign, 1986-1991)
The attraction of a space telescope over a ground telescope lie mainly in two areas. First, it is immune to the vagaries of the atmosphere, above all the phenomenon of turbulence, or "seeing," caused by constant, tiny fluctuations in the atmosphere above a telescope. While ideally a telescope will be limited in its maximum possible resolution only by the size of its optics, in the presence of seeing large astronomical telescopes behave as if they are much smaller than they actually are. Although large telescopes still offer advantages (mostly in terms of light-gathering area) that make them worth using, the presence of seeing sharply limits their capability compared to their theoretical limits. In space, however, there is no atmosphere, and therefore no seeing. In theory, this could allow a 10-20 fold increase in resolution, even with a relatively small 2.5 meter mirror, allowing astronomers to gather more detail on known objects and see smaller objects than had previously been possible. Secondly, a space telescope can detect many more wavelengths of light, and detect less intense sources of those wavelengths, than a ground telescope can. Even on a perfectly clear day, the atmosphere absorbs or reflects back into space about a fifth of incoming solar radiation. For many other wavelengths of radiation, such as infrared or high-energy bands, the atmosphere is practically opaque. Dim sources, such as distant galaxies, or sources which radiate primarily in those blocked bands, cannot be detected at the ground at all, requiring telescopes above the atmosphere to get even a glimpse.
These advantages had been identified by the American astronomer Lyman Spitzer as early as 1946, and amateur astronomers of a science-fictional bent had doubtlessly thought of these capabilities even earlier, but the technology of the time was simply nowhere near advanced enough to actually launch such a mission. Instead, astronomers had to accept the presence of seeing in ground-based telescopes, and rely on the glimpses of otherwise blocked radiation afforded by sounding rockets and balloon flights through the 1950s. However, with the launch of Sputnik the idea of putting a telescope in orbit no longer seemed so remote or difficult. Less than a year after Yuri Gagarin's first flight, NASA launched the first space observatory, dedicated to watching not distant galaxies but instead the Sun, the Orbiting Solar Observatory. In conjunction with ground observations and several other satellites, these would make the most in-depth study of the Sun over a single 11-year solar cycle in history. The eight OSO missions gave birth to the solar telescope that formed the scientific centerpiece of Skylab, and led directly to the network of space-based solar observatories that operate today, providing advance warning of solar flares and activity that can have significant economic impacts on Earth. However, they also helped validate the concept of the space observatory in general, leading to the Orbiting Astronomical Observatories later in the decade. These were the first of their kind, and the spectacular success of OAO-2 and OAO-3, along with the contemporary US-Italian Small Astronomical Satellite program, further proved the value of space-based observations. Like the OSOs, the OAOs were ultraviolet and x-ray observatories, focused on observing those wavelengths not visible at Earth's surface. Combined with indefatigable support by Spitzer, however, the idea of orbiting a large, visible-light telescope had gained traction, and in 1968 NASA officially started working on the idea. At the time, plans for the "Large Space Telescope" involved a 3 meter main mirror and extensive on-orbit servicing, all allowed by the planned "space shuttle". Additionally, while mainly oriented at visible observations, the LST (as it was then known) would also be capable of some ultraviolet and infrared observations, effectively allowing for three telescopes in one package.
With the demise of the space shuttle, however, and continuing budget pressures, these plans were increasingly scaled back. The first idea to be dropped was servicing. Although certainly possible through making the telescope part of a future space station, the relatively dirty vacuum surrounding any human-occupied space vehicle and the vibrations caused by human movement meant that it simply wouldn't be worth it. This would limit the telescope's operational lifetime to only 5-10 years before too many critical parts would likely fail to continue observation, and would also mean that the telescope would become increasingly out-of-date by the time it was actually retired. Worse, any difficulties with the instruments that could otherwise be corrected would have to be accepted by the astronomers. Still, it would offer significant advantages over existing telescopes, enough that there was little resistance to the need from the astronomical community. Next to fall was the size of the mirror, which acted as the major control of the overall cost, due both to the cost of launch and the cost of manufacturing such a large object to such precise tolerances. Eventually, a 2.5 meter mirror was agreed upon. While not as large as the original design, it offered significant savings and (when combined with the LST's unique environment) would still make the observatory top-class in terms of observing ability. Mirror fabrication was handled by the team of Eastman Kodak and Itek, who produced two separate mirrors that were then cross-checked against each other, ensuring that they were correctly fabricated to a hitherto unheard-of precision. Their competitor, Perkin-Elmer, had offered a strong bid relying on technologically advanced computer-controlled grinding machines, but the great experience of Kodak and Itek in space observation (each had been responsible for optics systems on board US spy satellites) and their use of proven techniques eventually won out over the promising but risky system proposed by the relative newcomer. Finally, an agreement was made with the nascent European Space Agency to provide some funds and materials for the telescope, in particular the solar panels responsible for powering its systems, in exchange for providing a permanent share of the observing time to European astronomers. The only one of the original capabilities the telescope would possess without modification was the ability to observe at infrared and ultraviolet wavelengths as well as visible wavelengths. As the project gradually picked up steam, the telescope finally acquired a real name: Hubble, after the famous American astronomer who demonstrated that the universe was not static, but expanding over time.
