The Hubble Telescope
In a 2004 interview with Ed Bradley on CBS News, astrophysicist and author Mario Livio said, "Ask any person the name of a playwright. Most of them would say Shakespeare. Ask them the name of a scientist. Most of them would say Einstein. Ask the name of a telescope. They will all say Hubble."
Initially costing 1.5 billion dollars, the Hubble Space Telescope (Hubble) was launched from the space shuttle Discovery on April 24, 1990. Fundamentally a moving observatory with an extraordinary camera, Hubble orbits the earth transmitting about 120 gigabytes of scientific data every week. This amount of information would translate to approximately 3,600 feet (1,097 meters) of books on a shelf.
Hubble uses a curved mirror to focus starlight in order to obtain its images. This mirror is located deep inside the telescope, protected by its long tube-like structure. Because there is no atmosphere in space, there is no risk of dust or corrosion reaching inside it.
Fabricated over the course of a decade, Hubble's primary and back up mirror were ground so that they do not deviate from a perfect curve by more than 1/800,000th of an inch. Simply stated, if Hubble's mirror was scaled up to the diameter of the Earth, the most pronounced protrusion would be six inches high.
Despite this incredible level of exactitude, the central region of the mirror proved a few nanometers too flat. This miniscule discrepancy resulted in disappointing blurred images. As a result, optical engineers constructed the Corrective Optics Space Telescope Axial Replacement (COSTAR). Essentially a contact lens for Hubble's mirror, COSTAR was mounted through a series of five space walks in December 1993. The successful installation of COSTAR remains one of the landmarks of human spaceflight.
Two images of a spiral galaxy taken before and after the corrective lens COSTAR was installed.
In addition to the precision of Hubble's mirror, the pointing accuracy of the telescope is equally astonishing. Hubble is able to lock onto a target without deviating more than 7/1000th of an arcsecond, or about the width of a human hair seen at a distance of 1 mile. This accuracy allows Hubble to position its four cameras properly. The cameras collect data on a broad visual spectrum that includes ultraviolet light, visible light, and near infrared light.
With the end of NASA's space shuttle program, Hubble's last servicing took place in May 2009. Because it can no longer be physically updated or repaired, the telescope will eventually breakdown. Scientists differ in their estimates of Hubble's remaining lifespan—some predicting it will begin to seriously degrade within the next two years. More optimistic approximations envision Hubble functional well into the next decade.
Hubble will leave behind an impressive legacy. The famed Hubble Ultra Deep Field (HUDF) photograph, revealed in 2004, remains the furthest image ever taken of space. The telescope has reshaped the way scientists understand the birth of stars, black holes, and the existence of dark matter. Perhaps of greatest significance, images taken by Hubble have allowed scientists to date the universe at 13 to 14 billion years old.