Hubble Telescope - A Giant In The Space!

The Big Bang theory explained the genesis of the universe, then the very next question we had was: How old is the cosmos? To answer this question it was necessary to build a new telescope. Some of the largest telescopes were then built such as the Mount Palomar 200-inch reflector, but it was soon clear that we need something else with it. All the mighty telescopes were built and were on the earth’s surface, it was necessary to have a telescope, which do not have to peer through the murky and turbulent atmosphere of the earth’s atmosphere, a telescope in the space!

Nearly a century ago, astronomers in the United States started building giant reflecting telescopes; those were unprecedented in size and vision. One of these, the 100-inch Mount Wilson reflector, was to make one of the greatest scientific discoveries ever. It was made by the astronomer Edwin Hubble. He looked at the distant galaxies with the reflector and discovered that the universe was expanding. The effect was named after the Habble’s law.

In 1946, an astrophysicist named Dr. Lyman Spitzer (1914-1997) proposed that a telescope in space would reveal much clearer images, of even farther-off objects, than any ground-based telescope. This was an outrageous idea, considering that no one had yet launched a rocket into outer space. As the US space programme developed and excelled in the 1960s and 1970s, Spitzer lobbied NASA and Congress to develop a space telescope. In 1975, Congress approved funds for the space telescope, and NASA named Lockheed Martin Aerospace Company as the prime contractor to oversee its construction.

The Hubble Space Telescope (HST) took 8 years to build, held five scientific instruments, consisted of more than 400,000 parts and had 26,000 miles of electrical wiring. HST 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, HST went into orbit in 1990. Almost immediately after it was deployed, astronomers found that they could not focus the telescope. They found that the primary mirror had been ground to a wrong dimension at the Perkin-Elmer Corporation’s factory. Although the defect in the mirror was less than one-fiftieth the size of a human hair, it caused the HST to suffer spherical aberration and produce fuzzy images.

Scientists came up with a replacement contact lens called COSTAR (Corrective Optics Space Telescope Axial Replacement) to correct the defect in the HST. COSTAR consisted of several small mirrors that would intercept the beam from the flawed mirror, correct the defect and relay the corrected beam to the scientific instruments at the focus of the mirror. COSTAR replaced one of the scientific instruments when it was installed during a 1993 servicing mission by shuttle astronauts. When the HST was tested after the servicing mission, the images were vastly improved. Now, all on the instruments placed in the HST have built-in corrective optics for the mirror’s defect, and COSTAR is no longer needed.

The Hubble Space Telescope (HST) has spent 10 years in space and is halfway though its orbital life. It has observed 14,000 celestial targets, gathered 3.5 terabytes of data and spawned 2,651 scientific papers. It has made essential contributions to our knowledge of the age and evolution of the universe. It has sharpened and extended our view of the cosmos.

The HST cannot observe the sun because the intense light and heat would fry its sensitive instruments. Therefore, the HST is always pointed away from the sun. In addition, the HST cannot observe Mercury or Venus because they are too close to the sun. Certain stars cannot be observed by the HST as they are too bright for some of its instruments. In addition to the brightness of objects, the orbit of the HST also limits what can be seen. Sometimes, targets are obstructed by the Earth itself during the orbit. This can limit the time spent observing a given object. Also, the HST passes through a section of the Van Allen Radiation Belts, where charged particles from the solar winds are trapped by the Earth’s magnetic field. These encounters cause high background radiation, which interferes with the detectors of the scientific instruments. No observations can be done during these periods.

Despite its flawed early history, the HST has performed well, yielding much scientific data and beautiful images. However, the HST will not last forever. Plans are underway for a new space telescope, called the Next Generation Space Telescope (NGST). NGST will be even more sensitive than HST and provide better images of even distant objects. The age of optical space telescopes started by HST promises to revolutionize astronomy as much or more than Galileo’s first use of the telescope did long ago.