Hubble Telescope

The Hubble Space Telescope is one of the most amazing machines in orbit right now. In 1946, an astrophysicist named Dr. Lyman Spitzer proposed that a telescope in space would reveal better and clearer images that are even far from earth than any ground telescope. This idea was very extravagant because no one had yet launched a rocket into outer space. As the US space program excelled quickly over the early years, Spitzer lobbied NASA and Congress to develop a space telescope. In 1975, the European Space Agency and NASA began to develop the telescope that would change astronomy for ever. In 1977, Congress approved funding for the development of the space telescope and NASA named Lockheed Martin Aerospace Company as the prime contractor to oversee its construction. In 1983, the telescope was finished and was named after Edwin Hubble, an American astronomer whose observations of variable stars in distant galaxies confirmed that the universe was expanding and gave support to the “Big Bang” theory.

The Hubble Telescope took a total of eight years to develop. It held five scientific instruments, had more than 400,000 parts, and had 26,000 miles of electrical wiring. The Hubble Telescope was reported to be 50 times more sensitive than ground-based telescopes with 10 times better resolution. After a long delay due to the Challenger disaster, the Hubble Telescope went into orbit in 1990. After being deployed, astronomers immediately found out that the telescope could not be focused. They found the problem and discovered that the primary mirror had been ground to a wrong dimension at the Perker-Elmer Corporation’s factory. Although the defect in the mirror was less than one-fifth the size of a human hair, it was enough for the Hubble Telescope to suffer from

spherical aberration, light reflected from the mirror’s edge gets focused to a slightly different point than light reflected from the center, and produce fuzzy, unclear images. Scientists came up with a solution to correct the defect in which they came up with a replacement “contact” lens called COSTAR. The Corrective Optics Space Telescope Axial Replacement consisted of several minute mirrors that would intercept the beam of the flawed mirror and relay the corrected beam to the scientific instruments at the focus of the mirror.

The Hubble telescope is a compound telescope design where light enters the telescope through the opening and bounces off the primary mirror to a secondary mirror. Then the secondary mirror reflects the light through a hole in the center of the primary mirror to a focal point behind the primary mirror. At the focal point, half transparent mirrors distribute the light to the various scientific instruments. The Hubble Telescope mirrors are made of glass and coated with multiple layers of pure aluminum that are three-millionths of an inch thick and a coat of magnesium fluoride that is one-millionth of an inch thick to make them reflect visible, infra-red and ultraviolet light. The primary mirror weighs 1825 pounds and the secondary mirror weighs in at 27.4 pounds.

By looking at the different wavelengths or the spectrum of light from a celestial object, you can tell many of its properties and features. To do this, the Hubble Telescope is equipped with various scientific instruments. Each instrument used CCD’s instead of photographic film to capture the light because it has higher resolution. The light that is detected by the CCD are digital signals, which are then stored in on-board computers, which then are relayed to earth to study and learn from. The digital data is then transformed into amazing pictures that we can look at on the news, online, magazines, and newspapers.

There are various scientific instruments that are needed for the Hubble Telescope. The Wide Field Planetary Camera 2 or WFPC2 is the main “eye” or camera of the Hubble Telescope. The WFPC2 has four CCD chips to catch the light. Three of the CCD chips are low resolution, wide-field CCD chips that are arranged in an “L” shape and one, high resolution planetary camera CCD chip inside the “L”. All four of the CCD chips are exposed to the target at the same time, and the target image is centered on the desired CCD chip in either high or low resolution. The WFPC2 can take images through various filters like red, green, and blue to make natural color pictures.

Another scientific instrument that is needed for the Hubble is the Near Infrared Camera and Multi-Object Spectrometer or NICMOS. Most of the time, interstellar gases and dust can create a barrier for our vision of visible light from various celestial objects.