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A Brief History of the Hubble Space Telescope
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by Gabriel Okolski
For more than 15 years, the Hubble Space Telescope has been providing scientists and the public with spectacular images of deep space. One of the most technologically advanced pieces of equipment that humans have put into orbit, Hubble has helped researchers make important discoveries about our universe, ranging from planets and stars to galaxies and cosmology. Thanks to incredible efforts of scientists and engineers, the telescope has also given astronomers insight into the history and fate of our universe.
Why a Space Telescope?
Although the Hubble Space Telescope has been in orbit since 1990, its origins date long before that. The first serious concepts of a space-based optical observatory began just after World War II. In 1946, Lyman Spitzer, a professor and researcher at Yale University, argued that a space telescope would offer great advantages over ground-based observatories. His paper, entitled Astronomical Advantages of an Extra-Terrestrial Observatory, explained that the Earth's atmosphere blurs and distorts light coming from stars. Even the most precise and advanced telescopes on the ground cannot escape this phenomenon, but a telescope in orbit can. Furthermore, the atmosphere blocks X-rays emitted from high-temperature phenomena in stars and other objects, so they cannot be detected by instruments on the Earth's surface. A space telescope would also allow scientists to accurately measure these emissions as well.
While teaching at Princeton University, Spitzer was asked to head a National Academy of Science Ad Hoc Committee on the Large Space Telescope. During the first meeting in 1966, this group performed comprehensive studies on possible uses for a large space-based telescope. In 1969, the committee published Scientific Uses of the Large Space Telescope, in which the National Academy of Science urged the construction of such an instrument. The report said that a large orbital telescope would make a "dominant contribution to our knowledge of cosmology," by helping scientists study stars, measure distances to galaxies, and investigate the physics behind our universe.
How it All Came Together
In order to move from concept to reality, the telescope needed support from NASA, the only agency likely to be able to execute the National Academy's recommendation. Wernher von Braun, one of America's leading rocket scientists who came from Germany after World War II, had already looked into the challenges of a space telescope with his team at the Marshall Space Flight Center in the 1960s. Other NASA studies had also originally called for space telescopes, albeit using smaller mirrors that the 120-inch size proposed by the National Academy of Sciences.
In the mid-1960s, NASA and its contractors conducted phased studies into the feasibility of a large space telescope. Although there was initial dissent within NASA over whether the agency should work its way up to a large-scale observatory or take one giant leap to the final product, the decision to develop the Space Shuttle program greatly improved the flexibility NASA would have in designing a space telescope. In 1971, George Low, NASA's Acting Administrator, gave approval to the Large Space Telescope Science Steering Group to conduct feasibility studies.
With NASA on board, the next step for what would become the Hubble Space Telescope was to obtain federal funding for the project. Unfortunately for the program, the large space telescope's total cost was roughly estimated at $400 to $500 million, making it a tough sell. Funding for the telescope was originally denied by the House Appropriations Subcommittee in 1975, but this prompted a large-scale lobbying effort by NASA and leading astronomers, led by Spitzer and John Bahcall, another Princeton astronomer who was also an original proponent of the telescope. The European Space Research Organization (ESRO), later to become the European Space Agency (ESA), was also invited to participate in the project by producing inexpensive solar panels and taking part in observations and research. NASA wanted to take advantage of international cooperation to reduce the overall cost of the program, making it more likely to receive Congressional support. The ESRO accepted the offer in 1975. A mirror reduction from 3 to 2.4 meters helped bring the project down to about $200 million, approximately half the originally expected price tag. The proposal was accepted by Congress, which granted the Large Space Telescope program funding in 1977.
The following year, design of the telescope began in earnest, with the award of contracts to the Perkin-Elmer Corporation to construct the mirror and optical assembly and the Lockheed Missiles and Space Company to construct the spacecraft and its support systems. The Europeans were mainly responsible for the solar array that would power Hubble while in orbit. Among the many technological advances used in the telescope's construction was the computer-based laser grinding system used by Perkin-Elmer to craft the observatory's primary mirror.
NASA originally planned to launch in 1983, but the program experienced a considerable delay. The Perkin-Elmer mirror was completed in 1981, but the entire optical assembly was not put together until 1984. Subsequent final assembly of the spacecraft did not take place until 1985. The year 1983 did have its own notable events however, with the founding of the Space Telescope Science Institute at the John Hopkins University in Maryland. A part of the Association of Universities for Research in Astronomy (AURA), the institute would be in charge of Hubble's scientific program. That same year would also see the naming of the telescope after Edwin P. Hubble, a notable astronomer who conducted extensive research into stars and galaxies and was the first to prove that the universe is expanding.
Launch, Fuzzy Photos, and a Spectacular Repair
With all of Hubble's pieces in place by December 1985, NASA planned for an October 1986 launch. But Hubble's future would be in limbo once again, when tragedy struck on January 28, 1986. On a cold morning, the Space Shuttle Challenger lifted off into the Florida sky, in what appeared to be a routine launch. Only a little more than a minute into the flight, the vehicle exploded into a ball of smoke and flame, calling into question when Hubble would make the trip into orbit.
When shuttle flights resumed in 1988, Hubble was finally launched aboard Discovery on April 24, 1990. The telescope's original equipment package included the Wide Field/Planetary Camera (WF/PC), Goddard High Resolution Spectograph (GHRS), Faint Object Camera (FOC), Faint Object Spectograph (FOS), and High Speed Photometer (HSP).
After a few weeks of operation, scientists noticed that images being sent back from Hubble were slightly blurred. While this distortion still allowed scientists to study the cosmos and make significant discoveries, it resulted in less spectacular images, and some of the original mission could not be fulfilled. An investigation finally revealed a spherical aberration in the primary mirror, due to a miscalibrated measuring instrument that caused the edges of the mirror to be ground slightly too flat. Engineers rushed to come up with a fix to the problem in time for Hubble's first scheduled servicing mission in 1993. The system designed to correct the error was designated COSTAR, for Corrective Optics Space Telescope Axial Replacement. COSTAR was a set of optics that compensated for the aberration and would allow all of Hubble's instruments to function normally.
In December, 1993, the crew of STS-61 embarked on a service mission to replace a number of Hubble's parts. Following intensive training on the use of new tools never used before in space, two teams of astronauts completed repairs during a record five back-to-back spacewalks. During the EVAs, COSTAR was installed and the Wide Field/Planetary Camera was replaced with the Wide Field/Planetary Camera 2, which was designed to compensate for the mirror problem. The team also performed basic maintenance on the craft, installed new solar arrays, and replaced four of Hubble's gyroscopes.
Shortly after the crew returned to Earth and the Hubble Space Telescope began returning sharp and spectacular images, NASA deemed the servicing mission a success. Astronomers could now take advantage of a fully functional space telescope, and the public was treated to breathtaking photos of stars, galaxies, nebulae, and other deep-space objects. Subsequent servicing missions improved Hubble's capabilities and performed routine repairs. In February, 1997, the crew of STS-82 installed the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) and the Space Telescope Imaging Spectograph (STIS) to detect infrared light from deep-space objects and take detailed photos of celestial objects. Servicing mission 3A in December, 1999 replaced all six of the telescope's aging gyroscopes, which accurately point the telescope at its target. STS-103 astronauts also replaced one of the telescope's three fine guidance sensors and installed a new computer, all in time to redeploy Hubble into orbit on Christmas Day. The most recent servicing mission to the spacecraft, servicing mission 3B, came aboard STS-109 in March, 2002. Columbia crewmembers installed the new Advanced Camera for Surveys (ACS), which had sharper vision, a wider field of view, and quicker data gathering than the Wide Field/Planetary Camera 2. Astronauts also replaced Hubble's solar panels with a more efficient array and conducted repairs on the NICMOS.
Hubble's Future
As it continued to return groundbreaking photos of the universe and help astronomers do valuable research, the Hubble Space Telescope's future would once again be thrown into uncertainty by a Space Shuttle tragedy. On February 1, 2003, all seven astronauts aboard Columbia were killed as their Space Shuttle disintegrated during reentry into the Earth's atmosphere. The resulting two-year period of investigations led to Administrator Sean O'Keefe's decision that future shuttle missions would go only to the International Space Station, where safe haven was possible, as well as inspection and repair of the Shuttle. Though the telescope was slated for servicing in 2005, O'Keefe concluded that another Hubble repair mission with the Shuttle would be too risky and ultimately rejected the option of sending another servicing mission. In late 2004 the National Academy of Sciences concluded that the risks were acceptable and recommended that a Shuttle mission should service Hubble after all. O'Keefe asked NASA's Goddard Space Flight Center to conduct feasibility studies into a robotic servicing mission.
Current Administrator Michael Griffin revisited the Hubble servicing mission decision and rejected the robotic servicing mission option, calling the $1 billion plan too costly. He has also revisited the idea of a Shuttle repair flight, and pending successful Shuttle operations in the near future, NASA is preparing to send a mission to Hubble before the Space Shuttle is retired by the end of the decade.
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