Hubble Telescope
Casey Korecki ME ‘03
The dream of putting a telescope into orbit, where it would be able to observe the heavens without interference from the Earth’s atmosphere, has its scientific roots as far back as 1923 when famed rocket scientist Herman Oberth first published a paper contemplating such a possibility. History was made on April 26, 1962 with the launch of Ariel 1 by Great Britain. The first astronomical satellite project, Ariel 1 paved the way for further space exploration as well as sparking the imagination and creativity of scientists worldwide. Today, the Hubble telescope, located 600 km above the Earth, gives scientists a view into distant galaxies that contain features seemingly unimaginable 75 years ago. By constantly challenging the current conceptions held about the universe and its components, Hubble pushes scientists toward a better understanding of our own solar system’s turbulent history.
Hubble History
Even as far back as only four years into NASA’s history, or 1962, the concept of a space-based telescope had the support of the National Academy of Sciences. The sentiment, echoed again in 1965 and 1969, was to be the fuel for the launch of two successful satellites for star observation. The first of these two satellites, creatively named Orbiting Astronomical Observatory 2 (or OAO-2), was launched December 7, 1968. OAO-2 contained 11 UV telescopes, which were used in detecting the first sign of UV radiation from the center of the Andromeda Galaxy M31, as well as recording a supernova in May of 1972. OAO-2 remained active for many years. Fueled by their success, NASA launched OAO-3 on August 21, 1972 and remained active until February of 1981. Soon renamed Copernicus, this telescope carried 4 co-aligned X-ray detectors as well as an impressive 80 cm UV telescope. Copernicus discovered several log period pulsars as well as observing rapid intensity variability from Centuri A. The success of the OAO project led to increased support for an orbiting optical space telescope. With the increased payload room made possible by the newly designed space shuttle, the dream seemed possible. A team of scientists began work on the basic design and selecting the instruments required in 1973. In 1977, congress approved funding, and the group expanded to 60 scientists from 38 institutions. Development and construction of the telescope fell into the hands of Marshall Space Flight Center in Huntsville, Alabama while the development of the scientific instruments and ground-control center was the responsibility of Goddard Space Flight Center in Greenbelt, Maryland. The European Space Agency also contributed, supplying solar panels arrays and one of the five scientific instruments. Marshall contracted Perkin-Elmer in Danbury, Connecticut to develop the optical and guidance sensors, while Lockheed Missiles and Space Company of Sunnyvale, California was selected to develop support systems, create the outer covering, and also assemble the telescope when all the parts were completed.
One of the most essential yet delicate pieces of hardware on board was the 8-foot diameter main mirror. It was completed in 1981 and was assembled into the Hubble telescope in 1985. While the original launching date for Hubble was in 1986, delays due to space shuttle redesigning after the Challenger accident forced the delay of the launch. Hubble was finally deployed on April 24, 1990 aboard the space shuttle Discovery. Hope for quick results and a flawless mission soon vanished when it became apparent that a small defect near the edge of the main mirror (1/50 the width of the human hair) was causing spherical aberration in the telescope. Scientists, undeterred by the flaw in the mirror, focused their attention on the other instruments that were not affected by the aberration including the ultraviolet and spectrographic equipment, and began facing the challenge of correcting Hubble’s fuzzy vision.
Fixing Hubble
While the error in Hubble’s main mirror was small in comparison to many Earthly objects, it was a major setback for scientists hoping to gain a clear image of far off galaxies. In order to correct the visual problem, scientists would have to come up with a series of lenses that would compensate for the flawed main mirror. In December 1993, the first Hubble servicing mission was carried out. Carried into orbit aboard space shuttle Endeavour, the Corrective Optics Space Telescope Axial Replacement (COSTAR) unit is a phone booth sized apparatus containing five corrective lenses. It was installed onto Hubble during a challenging five days of back to back space walks totaling 35 hours and 28 minutes. The successful correction of Hubble was not only a victory for those hoping to overcome the visual flaw in the mirror, but also a victory for those advocating the continuous upgrade and perfection of the Hubble systems. The crew of the Endeavour proved that modifications could be made to Hubble through space walks. Since then, a total of five servicing missions have taken place on Hubble. The most recent, occurring in February of 2002, implemented the Advanced Camera for Surveys (ACS). This camera will be able to produce 10 times as many pictures as the version it replaces. In addition, solar arrays were replaced and new power units and cooling systems were installed. The next planned space mission currently scheduled for July of 2003. One of the tentative functions of this mission will be to install a piece of equipment to replace COSTAR, which will no longer be necessary due to the removal of all the old systems requiring its use. Hubble is expected to remain in operation until around 2010, a full 20 years after its launch.
Hubble has many claims to success. It has provided information on 25,000 different targets, taking about 330,000 observations. Information collected and archived from Hubble has accumulated to over 7.3 terabytes, all stored at the Space Telescope Science Institute. The data has been presented in 2,663 scientific papers. However, perhaps the most compelling evidence for the declaration of Hubble’s success is the breathtaking photographs it has sent back over the years. These photographs have sparked imaginations worldwide, and have kept us all poignantly aware of how much we have yet to learn about our own existence.
SOURCES:
http://heasarc.gsfc.nasa.gov/docs/copernicus/copernicus.html
http://www-pao.ksc.nasa.gov/kscpao/chron/sts-61.htm
http://hubble.nasa.gov/overview/
http://fuse.pha.jhu.edu/pubinfo/jhuap.html
http://www.seds.org/hst/hst.html
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