Happy 22nd Birthday Hubble Space Telescope!

by / Wednesday, 25 April 2012 / Published in Blog - Space Log

Do you have a telescope? If you don’t go to your local science center or observatory and take a look through theirs; because since the earliest days of astronomy, since the time of Galileo, astronomers have shared a single goal — to see more, see farther, see deeper.


On this date in history, April 25th, 1990, the Hubble Space Telescope’s was launched by Space Shuttle Dicovery and gave humanity one of its greatest advances in ‘discovery.’ Hubble is a telescope that orbits Earth. Its position above the atmosphere, which distorts and blocks the light that reaches our planet, and gives it a view of the universe that usually surpasses that of ground-based telescopes.


Hubble was expected to last only about 10-12 years and is the telescope that just keeps on going and taking magnificent pictures. Hubble is one of NASA’s most successful and long-lasting science missions. It has beamed hundreds of thousands of images back to Earth, shedding light on many of the great mysteries of astronomy. Among its many discoveries, Hubble has revealed the age of the universe to be about 13 to 14 billion years, much more accurate than the old range of anywhere from 10 to 20 billion years. Hubble played a key role in the discovery of dark energy, a mysterious force that causes the expansion of the universe to accelerate.


Hubble has shown scientists galaxies in all stages of evolution, including toddler galaxies that were around when the universe was still young, helping them understand how galaxies form. It found protoplanetary disks, clumps of gas and dust around young stars that likely function as birthing grounds for new planets. It discovered that gamma-ray bursts — strange, incredibly powerful explosions of energy — occur in far-distant galaxies when massive stars collapse. And these are only a handful of its many contributions to astronomy. The sheer amount of astronomy based on Hubble observations has also helped make it one of history’s most important observatories. More than 6,000 scientific articles have been published based on Hubble data.


The Hubble Space Telescope is the direct solution to a problem that telescopes have faced since the very earliest days of their invention: the atmosphere. The quandary is twofold: Shifting air pockets in Earth’s atmosphere distort the view of telescopes on the ground, no matter how large or scientifically advanced those telescopes are. This “atmospheric distortion” is the reason that the stars seem to twinkle when you look up at the sky. The atmosphere also partially blocks or absorbs certain wavelengths of radiation, like ultraviolet, gamma- and X-rays, before they can reach Earth. Scientists can best examine an object like a star by studying it in all the types of wavelengths that it emits.

Newer ground-based telescopes are using technological advances to try to correct atmospheric distortion, but there’s no way to see the wavelengths the atmosphere prevents from even reaching the planet. The most effective way to avoid the problems of the atmosphere is to place your telescope beyond it. Or, in Hubble’s case, 353 miles (569 km) above the surface of Earth.


Every 97 minutes, Hubble completes a spin around Earth, moving at the speed of about five miles per second (8 km per second) — fast enough to travel across the United States in about 10 minutes. As it travels, Hubble’s mirror captures light and directs it into its several science instruments.


Hubble is a type of telescope known as a Cassegrain reflector. Light hits the telescope’s main mirror, or primary mirror. It bounces off the primary mirror and encounters a secondary mirror. The secondary mirror focuses the light through a hole in the center of the primary mirror that leads to the telescope’s science instruments. People often mistakenly believe that a telescope’s power lies in its ability to magnify objects. Telescopes actually work by collecting more light than the human eye can capture on its own. The larger a telescope’s mirror, the more light it can collect, and the better its vision. Hubble’s primary mirror is 94.5 inches (2.4 m) in diameter. This mirror is small compared with those of current ground-based telescopes, which can be 400 inches (1,000 cm) and up, but Hubble’s location beyond the atmosphere gives it remarkable clarity.

Once the mirror captures the light, Hubble’s science instruments work together or individually to provide the observation. Each instrument is designed to examine the universe in a different way.


And Hubble began with an idea 67 years before it was ever launched. The idea for the space telescope arose in 1923, when German scientist Hermann Oberth, one of the founders of rocketry, suggested blasting a telescope into space aboard a rocket. In 1946, Lyman Spitzer Jr., an American astrophysicist, wrote a paper proposing a space observatory. He would spend the next 50 years working to make the space telescope a reality. Spitzer was one of the main forces behind several of the orbiting observatories of the time, including the Copernicus satellite and the Orbiting Astronomical Observatory. His diligent advocacy helped spur NASA to approve the Large Space Telescope project in 1969. Because of budget considerations, the original proposal was downsized somewhat, decreasing the size of the telescope’s mirror and the number of instruments it would carry.

In 1974, the group working on the project suggested a telescope with a number of interchangeable instruments. They would be able to resolve at least one-tenth of an arcsecond and study wavelengths that ranged from ultraviolet to visible and infrared light. The Space Shuttle would be used to put the telescope in orbit and either return it to Earth for repairs and replacement instruments, or service it in space.In 1975, the European Space Agency began to work together with NASA on a plan that would eventually become the Hubble Space Telescope. In 1977, Congress approved funding for the telescope.


Almost immediately after Hubble went into orbit, it became clear that something was wrong. While the pictures were clearer than those of ground-based telescopes, they weren’t the pristine images promised. They were blurry. Hubble’s primary mirror, polished so carefully and lovingly over the course of a full year, had a flaw called “spherical aberration.” It was just slightly the wrong shape, causing the light that bounced off the center of the mirror to focus in a different place than the light bouncing off the edge. The tiny flaw — about 1/50th the thickness of a sheet of paper — was enough to distort the view. Fortunately, scientists and engineers were dealing with a well-understood optical problem — although in a wholly unique situation. And they had a solution. A series of small mirrors could be used to intercept the light reflecting off the mirror, correct for the flaw, and bounce the light to the telescope’s science instruments. The Corrective Optics Space Telescope Axial Replacement, or COSTAR, could be installed in place of one of the telescope’s other instruments in order to correct the images produced by the remaining and future instruments. Astronauts would also replace the Wide Field/Planetary Camera with a new version, the Wide Field and Planetary Camera 2 (WFPC2), that contained small mirrors to correct for the aberration. This was the first of Hubble’s instruments to have built-in corrective optics. Astronauts and NASA staff spent 11 months training for one of the most complex space missions ever attempted. In addition to the critical nature of the mission, it would be the first test of the telescope’s vaunted ability to be serviced and repaired in space. transferring about 120 gigabytes of data every week.


Hubble’s successor, the James Webb Space Telescope (JWST), is currently in the works. JWST will study objects from the earliest universe, objects whose light has “redshifted,” or stretched into infrared light. From its orbit 940,000 miles (1.5 million km) away from Earth, JWST will unveil secrets about the birth of stars, solar systems and galaxies by peering through the dust that blocks visible light. The telescope is scheduled to launch this decade.


Eventually, Hubble’s time will end. As the years progress, Hubble’s components will slowly degrade to the point at which the telescope stops working. When that happens, Hubble will continue to orbit Earth until its orbit decays, allowing it to spiral toward Earth. Though NASA originally hoped to bring Hubble back to Earth for museum display, the telescope’s prolonged lifespan has placed it beyond the date for the retirement of the space shuttle program. Hubble was designed specifically to function with the space shuttle, so the replacement vehicle will likely not be able to return it to the ground. A robotic mission is expected to help de-orbit Hubble, guiding its remains through a plunge through the atmosphere and into the ocean. But Hubble’s legacy — its discoveries, its trailblazing design, its success in showing us the universe in unparalleled detail — will live on. Scientists will rely on Hubble’s revelations for years as they continue in their quest to understand the universe.


Hats off to you dear Hubble!  Thanks for the glorious pics!