Among the reasons NASA wasn't as enthusiastic as the general public and America's school-age kids, to perform a final Hubble Telescope servicing mission, now scheduled as perhaps the last scheduled mission of the Space Shuttle Altantis later this summer, is the James Webb Space Telescope, under construction and slated for flight and "first light" in 2013.Naturally, following the decision to retire the three remaining Shuttles after the Columbia disaster in February 2003, both the risk and cost were considered too high. But NASA also knew, as magnificent as Hubble has been, even its astounding capabilities had long been overshadowed by those planned for follow-up missions such as the Webb.
The Hubble concept, after all, was born at the same time as that of the Shuttle itself, beginning in 1972. Originally both were supposed to be in service by 1976 and in time for the America's Bicentennial.
The Shuttle's cargo bay was planned around the dimensions of the Hubble, but the new technologies necessary for the eventual success of both projects, and endless budget cutbacks following the scrapping of Apollo, delayed both for many years. Columbia did not fly until 1981 and an additional decade, almost 15 years after its planned deployment, Hubble was finally carried into orbit, along with an embarrassing micro-flaw in the main mirror putting it in need of innovative corrective lenses installed in an "inherently dangerous" servicing mission, before it began to live up to its full potential.
Along with the easily ruptured spacesuits from wriggling pressurized fingers in places they weren't ever meant to poke, the Hubble flies more than 100 kilometers higher than the Shuttle's design, and closed to the Van Allen radiation belts, increasing the lifetime probability of "REID," or "Radiation Exposure Induced Death," which NASA protocols limit to 3 percent per astronaut, per career. While the Hubble flies closer to the Equator than the Space Station, even operations of the mission are limited during its passing though the fringe of the South Atlantic Anomaly, where the inner Van Allen Belt dips to its closest point to Low Earth Orbit.
Trips through the Van Allen Belt are hazardous, but not the killing field they are often made out to be by those who claim the Apollo lunar missions were frauds perpetrated on the world.
Yet another reason to eventually de-orbit the Hubble is the eventual erosion of the telescope due to prolonged exposure to Cosmic Rays of high energy and mass, particularly during Solar Minimums, when CR's are less attinuated by as much as 50 percent by a stronger solar influence during Solar Maximum. Space is wrongly considered not be an erosive environment, but more is constantly at work on humans and equipment than repeated exposure to stark heat and cold as the vehicle passes from dark shadow to full sunlight during most orbits.
This is another reason even the improved shielding built into the International Space Station cannot last forever. NASA now plans to decommission the Station, which is only 80 percent complete, in 2016.
Even so, Hubble's primary collecting mirror is "only" two and a half meters wide. The development of active, segmented and binocular earth bound telescopes have nearly overcome the very limitations of being down on Earth and under the shifting atmosphere that Hubble was designed to address, with the exception of baselines wider than any available on Earth or what can be constructed inside Earth's gravity well - the very limitations that once made the Hale Telescope on Mount Palomar in 1936 "the largest telescope possible."
By contrast, the James Webb Space Telescope will boast a mirror five meters in diameter, with seven times the light collecting ability. And beyond this, NASA is thinking even larger, with concepts using liquid metal mirrors stationed on the Moon.
"The (LMT) telescope would be anywhere from 66 feet to 328 feet wide," writes William Harris of "How Stuff Works."
"It would collect 1,736 times more light than Hubble and penetrate the depths of the (optical) universe," Harris explains, giving Webb the ability to resolve the very beginnings of the end of the "Cosmic Dark Age," and the first sudden proliferation of stars after the early Universe's beginning, and with unimaginable detail revealed of the "realm of the blue galaxies," today mere smudges on Hubble's famous and astounding Deep Field images.
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