Hubble Space Telescope

The Hubble Space Telescope has been one of the most remarkable achievements of modern space exploration. It was launched from the Space Shuttle into lower Earth orbit at an altitude of roughly 353 miles in 1990. Even at that altitude above the Earth, its orbit will gradually decay due to atmospheric drag. Yes, even at an altitude of 353 miles there are some very thin remnants of atmosphere left. Some decisions will have to be made in the future as to the continued operation of the Hubble Space Telescope because of this. The Hubble Telescope was named after the famed astronomer Edwin Hubble, who is generally regarded as one of the greatest astronomers of all time. It is able to let us see deep into the Universe in a way never before possible since it is unencumbered by the constraints of Earth-bound telescopes which have to do their observations through a thick layer of Earths atmosphere – even at higher elevations the atmosphere is still quite substantial – as well as excessive light ‘pollution’ in the night sky. The Hubble Telescope has been incredibly successful since its launch in 1990 with numerous remarkable discoveries about our Universe – we will mention some of these later. Let’s get some basic facts about this magnificent telescope and find out more about it.

The Hubble Space Telescope was actually in the planning stage for a number of decades before its actual deployment in 1990. Astrophysicist Lyman Spitzer wrote a paper in 1946 about the great benefits of having a telescope in space and what remarkable discoveries might be made with an observational platform well outside the Earths thick atmosphere – we would be able to see further and clearer into the Universe than ever before. Incidentally, this 1946 date was long before NASA was even established in 1958. Despite Spitzer’s enthusiasm and constant lobbying for a space-based telescope, it wasn’t until 1977 that the U.S. Government finally approved funding for such a project which would later be named Hubble.

The explosion of the Space Shuttle Challenger in 1986 greatly slowed down the planned deployment of the Hubble Telescope since Space Shuttle launches were temporarily stopped to try to correct what had caused the Challenger disaster – the Hubble Space Telescope had no ride into space since it was unable to be launched with more traditional rocket launches. Not only that, but the cost of the project went up precipitously because of long years of storage in high tech clean room facilities. Eventually, the Hubble Telescope was launched April 24th, 1990 aboard the Space Shuttle Discovery years behind schedule and more than 1 billion dollars over budget. But Hubble’s troubles were not over. Later in 1990 when astronomers viewed the first images from the Hubble Telescope, they were shocked and upset to find out that the images were out of focus; it wouldn’t come close to fulfilling its great potential with this terrible situation. It was soon discovered that the Hubble Telescopes mirror had been polished to the wrong specifications creating what is known as a spherical aberration. Although this aberration was only about one-fiftieth the diameter of an average human hair, it was enough to make the images from Hubble fuzzy and somewhat indistinct, far from the crisp and stunning images that were expected. Even the media made fun of Hubble; Newsweek called it the 1.5 billion dollar blunder on its cover. Things were looking pretty grim for a while, but the space scientists would not give up and they finally came up with a solution. They first calculated the conic constant of Hubble’s mirror and then made calculations for the needed correction. Then they developed a device called the Corrective Optics Space Telescope Axial Replacement, or COSTAR for short, which would be like giving the Hubble Telescope a pair of glasses to correct its focusing problems. Some new technical limitations of attaching this device to Hubble were found, where it was determined that at least one of its scientific instruments would have to be removed for COSTAR to work properly. Finally, the decision was made to remove the High Speed Photometer and plans were made to install COSTAR. The Space Shuttle Endeavour was launched on December 2nd, 1993 with COSTAR aboard; two space-walking teams over the course of five days successfully installed this device and the rest is history as they say. Ever since that December 1993 correction of Hubble, it has consistently delivered jaw-dropping and stunning images of the Cosmos and allowed humans to look farther into the Universe than they ever could have imagined!

In late 1995, something amazing happened with the Hubble Telescope. Scientists pointed Hubble at what seemed to be an empty area of the sky continuously for a period of 10 days, not really expecting to find that much. But what they found was absolutely amazing; in that seemingly empty part of the sky which was only the size of a grain of rice held at arms length, they found a huge number of galaxies – over 1500 – that had never been seen before, some of which were the most distant star systems ever discovered. In 2004 astronomers repeated a similar experiment and this time over 5000 galaxies was on the images, some of them were up to 13.2 billion light-years away. This is, in fact, a way of looking 13.2 billion years back in time giving us more insight into the early Universe and indeed the Big Bang itself.

There is a very interesting fact about the Hubble Telescope; in spite of the remarkable color pictures that we have seen over the years of galaxies, supernovae, and other deep space celestial objects, Hubble only takes pictures in black and white. The color photos seen are post-production ones where astronomers have added various color filters for different wavelengths of light – red, green, ultraviolet, and so on – to create the magnificent images that we see as a single color composite. Sometimes additional color is even added to the images to bring out details that would normally be invisible.

The Hubble Space Telescope, being well beyond Earths thick atmosphere, is so powerful that it can resolve a lightning bug over 7000 miles away(of course we know that there are no lightning bugs in space!). So it is not surprising that with this kind of optical power Hubble has given us a much more complete view of the Universe and, in fact, raised some really interesting questions. Being able to view stars up to 13.2 billion light-years away, the Hubble Telescope has given us a much better idea of the Big Bang and how it might have occurred, dating it at about 13.7 billion years ago. Thanks to Hubble, we now have very good evidence of incredibly massive black holes in Andromeda and other nearby galaxies; even our own Milky Way galaxy is suspected of having a huge black hole in its center. Earth-like planets orbiting nearby stars have been discovered thanks in large part to Hubble and this may be the first step in finding out that Earth humans are not alone in the Universe. The study of various supernovae has given us some very compelling ideas that there may be a strange force called dark energy which is causing the Universe to expand at a much faster rate than previously thought. Let’s now explore some of the Hubble Telescopes discoveries in a little more detail.

Here are just some highlights of the discoveries and insights gleaned from the Hubble Space Telescope; to list all(or even most) of them would take a large book and is beyond the scope of this article. Having said that, here are just a few of the most intriguing discoveries.

Dark Matter is invisible, as the name implies, but its presence can be confirmed by the gravitational effects it has on celestial bodies, such as galaxies, and the resultant distortion of light. Hubble’s examination of the light from very massive objects in the Universe such as galaxies has given us a much deeper insight into the nature of Dark Matter and how it behaves – it has gravitational effects just like normal matter. By analyzing the distortions of light from these galaxies, Hubble has enabled scientists to build a three-dimensional map showing the distribution of Dark Matter in the Universe. Of course, Dark Matter is still very mysterious and much is as of yet unknown, but this was a huge early step in trying to understand this exotic and strange substance.

Two new moons of Pluto were discovered which were named Nix and Hydra. Also, a new planet beyond Pluto was discovered which has been named Eris. Eris is about 27 percent more massive than Pluto and with its discovery raises the hope of finding even more planets deep in the Kuiper Belt.

Gamma ray bursts have been one of the most mysterious phenomena observed in our Universe. A gamma ray burst is so intense that it is indicative of an energy release in a few seconds much greater than that of the Sun in its entire 10 billion year lifetime. Thanks to the Hubble Telescope much more has been learned about the cause of these strange and massive bursts of energy. Galaxies in a stage of forming stars are a typical source of these gamma ray bursts; the more massive stars tend to collapse easier and form black holes, which then cause the huge energy release in the form of gamma rays as the stellar matter is consumed. More massive galaxies, including the Milky Way, have gigantic black holes in their center which has aided in their evolution.

Dark Energy is another very strange phenomena in the Universe which Hubble has shed some light on, but has also raised some more questions about at the same time. In the process of establishing the age of the Universe at about 13.7 billion years, observations by the Hubble Telescope have indicated that it is expanding at a much more accelerated rate than previously thought. Dark Energy seems to be the cause of this accelerated expansion and is now believed to account for at least 74 percent of all the mass and energy in the Universe. Scientists currently have very little understanding of Dark Energy, but as more about it is learned in the future, Physics, as we understand it today, could undergo a great revolution – only time will tell.

Hubble Space Telescope has greatly enhanced our understanding of extrasolar planets; that is planets orbiting other stars than our Sun. So far over 400 of these worlds have been discovered, and most of them by ground-based telescopes. But the power of Hubble has given us more information about their atmospheres, sizes, and other characteristics. These include some Earth-like planets which could contain some form of life.

Because of Hubble, it is now believed that all of the larger galaxies with a bulge of stars has an incredibly massive black hole in their center. This seems to indicate that black holes play an important role in the evolution of galaxies. It should be noted that much smaller galaxies – star clusters for example – without this bulging effect probably do not have black holes at their center.

Since observations from the Hubble Telescope has helped to establish the age of the Universe at about 13.7 billion years, it has enabled scientists to go literally back to almost the very beginning of time. These new insights have changed and expanded our knowledge of the evolution of our Universe, including the formation of stars and galaxies and even planets themselves. No doubt new exciting discoveries await us in the future!

The Hubble Space Telescope was manufactured by the spacecraft division of Lockheed and the optics(mirror, etc.) was manufactured by PerkinElmer. It was launched on April 24th, 1990 tucked away inside the cargo bay of the Space Shuttle Discovery from the Kennedy Space Center. May 20th, 1990 was when it first became operational. It weighs about 24490 pounds which is the weight of about 3 large hippopotamuses. Hubble is approximately 43.3 feet long and 13.8 feet wide; this is roughly the size of a large school bus. It uses solar panels for energy and operates on only about 2800 watts – about the energy required by 2 hairdryers.

The main mirror is a variant of the Cassegrain reflector telescope called a Ritchey-Chretien reflector. This has the advantage of a wider field of view than a traditional reflector telescope. The mirror itself has a diameter of about 95 inches with a very slight spherical aberration as explained earlier which is corrected by the COSTAR attachment(installed December 1993). It has a focal length of about 2268 inches with a focal ratio of f24. The collecting area of the mirror is approximately 7013 square inches and it can collect infrared, visible light, and ultraviolet wavelengths of the electromagnetic spectrum.

The Hubble Telescope is in low Earth orbit with a maximum altitude of 336.1 miles and a minimum altitude of 333.7 miles – this is a nearly circular orbit with an eccentricity of only about .000283. It makes a revolution around the Earth about every 95.42 minutes at a velocity of roughly 16992 miles per hour – this is the equivalent of about 15.1 orbits around the Earth every day(24 hours).

There were basically 5 Hubble Service Missions known as Servicing Mission 1, Servicing Mission 2, Servicing Mission 3A, Servicing Mission 3B, and Servicing Mission 4 as follows:

As described earlier, it was found that the Hubble Telescope had a faulty mirror. A solution was found by installing the COSTAR device to correct this focusing problem by the Space Shuttle Endeavour in December 1993. To do this it was necessary to remove the High Speed Photometer to make room for COSTAR. The solar arrays and related electrical components, as well as four gyroscopes and two magnetometers were also replaced. In addition to this, a coprocessor upgrade was made to Hubble’s computers and the Hubble Telescope was boosted to a higher orbit to delay its eventual orbital decay and extend its life. By January 1994 it was determined that this mission was successful.

The Space Shuttle Discovery flew Servicing Mission 2 in February 1997 and installed the Space Telescope Imaging Spectrograph and the Near Infrared Camera and the Multi-Object Spectrometer. A science tape recorder was also replaced with a solid-state recorder and some thermal insulation was repaired. The solid nitrogen heat sink of the Multi-Object Spectrometer, unfortunately, came into contact with an optical baffle which reduced the instruments expected lifetime from 4.5 to 2 years.

Servicing Mission 3A was flown by the Space Shuttle Discovery in December 1999 replacing all 6 onboard gyroscopes of Hubble(4 of the original 6 had failed) and also replaced the old computer with a new one with a more modern programming language – this new computer was 20 times faster with 6 times more memory than the original one. A Fine Guidance Sensor, a Voltage and Temperature Improvement Kit for the battery, and thermal insulation blankets were also replaced.

Servicing Mission 3B was flown by the Space Shuttle Columbia in March 2002; a new instrument called the Advanced Camera For Surveys was installed which essentially eliminated the need for COSTAR since there was a built-in correction for the spherical aberration of the Hubble Telescope. A closed cycle cooler was also installed in the Mult-Object Spectrometer(damaged earlier by liquid Nitrogen) to bring it back to life. Finally, the solar arrays were replaced for the second time which provided Hubble with 30 percent more power.

Servicing Mission 4, scheduled for February 2005, was delayed by the Columbia disaster in 2003 – Columbia disintegrated upon reentry into Earths atmosphere. The shuttle program was grounded for some time and even after the resumption of flights, there was some reservation about the cost and risks of this final Hubble Servicing Mission. Then in April 2005 a new NASA administrator, Michael Griffin, replaced Sean O’Keefe; he had an engineering background instead of the accounting background of O’Keefe and understood the problem much better. In October 2006 Michael Griffin gave the final go-ahead for Service Mission 4 to Hubble and scheduled the Space Shuttle Atlantis for an 11-day mission in October 2008. But there was a failure of Hubble’s main data-handling unit in September 2008 and the mission was postponed. Finally, in May 2009 Space Shuttle Atlantis flew Service Mission 4 which replaced the data-handling unit, installed improved nickel hydrogen batteries, Wide Field Camera 3, the Cosmic Origins Spectrograph, the Soft Capture and Rendezvous System, and other components. Except for the High Resolution Channel of the ACS, which could not be repaired, the Hubble Space Telescope was returned to fully functional status.

The service contract for the Hubble Space Telescope has been extended by NASA until June 2021. Although it is in an Earth orbit over 330 miles high, atmospheric drag will eventually cause Hubble to come crashing to Earth – the atmosphere is extremely tenuous at that altitude but there is still some atmospheric drag present. Depending on how active the Sun is and the extent of its effect on the upper atmosphere, the projected demise of Hubble is somewhere between 2028 and 2040, unless action is taken to deorbit it sooner for safety reasons(some parts of Hubble may survive reentry and reach Earths surface which could be a potential hazard).

The James Webb Space Telescope will probably be the most immediate successor to the Hubble Space Telescope with a tentative planned launch date in late March of 2021 on an Ariane 5 rocket in cooperation with the European Space Agency from Kourou ELA-3, a spaceport in French Guiana, South America. It is designed to operate much further away from the Earth at the L2 Lagrangian point where potential heat and light interference from the Earth and Moon are much less. James Webb Telescope is designed to observe objects in the Universe farther away from Earth than ever before, even beyond the ability of Hubble. The Hubble Space Telescope has helped to pave the way for a very bright future of space exploration!

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