From earliest mankind to only about 400 years ago, all that we knew about our universe was what we could see with the naked eye. In 1610, Galileo started studying the skies with his telescope and made discoveries that would change our perspective forever. He observed that Saturn had rings and many planets had moons. What looks like a faint cloud across the sky was not a cloud at all, but is the Milky Way, a collection of millions of stars, our closest galaxy.

In the centuries that followed, telescopes grew in size, complexity and, of course, ability to see farther and in greater detail. They were placed far from city lights and on mountain tops above the haze of the atmosphere. In the 1920s, the largest telescope of that time at the Mt. Wilson Observatory in Southern California was used to discover galaxies beyond our own.

Since that time, telescopes have been getting larger, computerized, more sophisticated and powerful. They could see farther in distance, which is also in time.

When we see an object in the heavens, the light we are observing started its journey toward us at a time in the past. That distance and time is normally measured in light years, hours or minutes.

For example, our sun is 8.3 light minutes away, Pluto 5.5 light hours, and the nearest star, aside from our sun, is just over four light years distant.

In 1979, design began on The Large Space Telescope, which would be put in an orbit 340 miles above the Earth. In 1983, it was renamed the Hubble Space Telescope, after the renowned astronomer Edwin Powell Hubble, who proved the existence of other galaxies and discovered the first evidence of an expanding Universe.

The Hubble would be an observatory in space, the first and largest major optical telescope to be placed there. Above the distortion of the atmosphere and free from interference of clouds, pollution and light, Hubble would have an unobstructed view of the universe. Scientists and astronomers would use it to record stars and galaxies billions of light years distant, as well as details of the planets in our solar system not seen before.

Ground construction of this huge satellite was completed in 1985, but the launch was delayed by the Challenger accident in 1986, which grounded all Shuttle flights.

The telescope was finally launched from Kennedy Space Center, Fla., and deployed in orbit by the Space Shuttle Discovery in April 1990, marking the most significant advance in astronomy since Galileo’s telescope.

Unfortunately, the first images from Hubble revealed that the main mirror (almost 8 feet in diameter) had a spherical aberration which caused all images to be blurred. A fix would be necessary.

So, in 1993, Shuttle spacewalking astronauts installed COSTAR, a complex package of five optical mirror pairs that would rectify the distortion. It would be the first of five servicing missions performed in order to replace failing components or to extend Hubble’s life. The last service mission was in 2009. Because the Shuttle program ended in 2011, there is presently no way to perform any further servicing or updates.

Hubble, about the size of a school bus, weighed about 24,000 pounds at launch and currently weighs close to 27,000 pounds after modifications. It has no thrusters. In order to change pointing angles, it uses Newton’s third law (for every action, there is an equal and opposite reaction) by spinning its gyros in the opposite direction, which turns it at about the speed of a minute hand on a clock, taking 15 minutes to turn 90 degrees.

Hubble has traveled more than 3 billion miles along a circular low Earth orbit taking pictures of distant planets, stars and galaxies. It has a pointing accuracy of .007 arc seconds, which is like being able to shine a laser beam on a dime 200 miles away. It can see astronomical objects with an angular size of 0.05 arc seconds, which is like seeing a pair of fireflies in Tokyo from Florida.

In 2013, images taken by Hubble showed seven primitive galaxies that formed more than 13 billion years ago. The galaxies were seen as they were close to the beginning of the Universe. Earlier this year, celebrating its 25th anniversary, Hubble observed never before seen images of a distant exploding star.

Over its lifetime, Hubble has made more than 1.2 million observations, and astronomers using its massive data have published more than 12,800 scientific papers, making it one of the most productive scientific instruments ever built. It has changed how we view the universe and our place within it.

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Marcus Goodkind of Tuckasegee, a retired aerospace engineer, worked with the National Aeronautics and Space Administration as a manager at Kennedy Space Center on all the manned programs from Mercury to Shuttle, including Apollo 11, the first manned lunar landing.