Eagle nebula showing birth of a new star [http://www.nasa.gov/images/content/115340main_image_feature_330_ys_full.jpg]
Astronomy is a unique science in that it studies the past to discover what the future may hold in store. It deals on scales unimaginable to human mind by using man-made instruments and fundamental laws of science. Perhaps the most significant and well known instrument used in recent history is the Hubble Space Telescope (HST). Launched in 1990, the Hubble Space Telescope has been our eye on the Universe ever since. It was designed to orbit 500km above Earth, beyond our atmosphere which scatters incoming light and hinders image quality. That is its main advantage over its Earth bound counterparts.
However, when it was launched in 1990, Hubble's first images of the Universe were fuzzy and unclear. It was later discovered that there was a design flaw in its 2 metre wide primary mirror. Little to say this was devastating news to everyone involved in the project as well as the general public. Initially the plan was to bring Hubble back to Earth for repairs. However the main question was, once it came back to Earth, would it be re-launched ever again? Then engineers and scientists came up with another plan to send a refurbishment mission comprised of top-notch astronauts with extensive training. The men and women of STS-61 servicing mission successfully repaired the HST and initiated one of NASA's most successful missions so far. Since that repair took place, Hubble has been able to bring excitement to millions of people around the world and produce some of the most spectacular images ever taken by man.
When Hubble unleashed its power and began showing us some of the most beautiful images imaginable we stood and watched in awe. For example, auroras of Jupiter and Saturn could clearly be seen and captured by Hubble. As opposed to lasting a few minutes like on Earth, auroras on these two gas giants would last for days, producing eerie images 3/4 of a billion kilometres away from Earth. Another event spotted by Hubble was Jupiter's gravitational dominance over near by comets, when in 1994 the ill fated comet Shoemaker-Levy 9 entered its atmosphere, fragmented and created large dark marks (impact "craters" or holes in the upper layers of atmosphere).
To answer the long standing question of how the solar system formed, Hubble pointed its mirrors on the far outreaches of Universe and began studying regions where stars were being produced (such as the famous Eagle nebula) since traces of our own history within the solar system have long been lost.
Eagle nebula showing birth of a new star [http://www.nasa.gov/images/content/115340main_image_feature_330_ys_full.jpg]
In these nebulae, what essentially happens is huge pillars of Hydrogen gas heat up to 1 billion degrees Centigrade which "triggers" the star engine and begins the essential process of converting Hydrogen into Helium. The energy of the star blows off the cacoon of gas surrounding it and proto-planetary disks form around the new stars. They eventually develop into planetary systems. Large stars live for a shorter period of time than smaller ones (5-10 million years as opposed to 10 billion years, such as our own Sun). Once they use up all of their fuel, the core shuts off and depending on their size, they seize to exist in various different ways (supernovae explosions, black holes, etc).
Hubble gave us an insight into how individual stars are created and destroyed, but it also showed us that the Universe is a very violent place where sometimes, for example, new galaxies may be formed as a result of two already existing galaxies colliding with each other. But to understand how the first galaxies were formed, Hubble focused its attention on a small piece of sky called the Hubble Ultra Deep Field which is the oldest piece of sky ever photographed in visible spectrum. From this image we learned that the first galaxies in the Universe were very different in size, shape and colour. Using this information, we devised a theory which suggests that 14 billion years ago the "Big Bang" initiated the process of galaxy formation and they began to drift away from each other.
The next question is, how will the Universe end (if it ends at all)? There are a number of varying theories which can answer this question. However, most of those theories are based on how much matter is contained within the whole Universe. If there is enough matter, the Universe will collapse on itself. But we know from all our observations that there isn't nearly enough visible matter for this to occur. Furthermore, Hubble discovered that the Universe is expanding - at an accelerating pace! It seems as if there is a repulsion force present in the Universe and it's driving everything apart. Could the missing matter account for phenomenon? To get an answer to this question, we need to be able to look at the edge of the Universe, but Hubble is not powerful enough to do this.
A telescope which may be able to help us with this question is the James Web Space Telescope (JWST) scheduled for launch in 2013. It is much larger than Hubble and houses an enormous 6.5 metre primary mirror which will be able to spot 100 times fainter objects than Hubble. It will orbit 1.5 million kilometres away from Earth, at a place called the Second Lagrange Point (L2) in order to operate in a cold and dark environment which is of paramount importance to infrared wavelength operations (as well as to remain in an orbit which makes operations and communication easy). Sunshields the size of a tennis court will keep the sunlight from damaging its equipment as it uses its 18 piece segmented mirror to view the most distant objects in the Universe and look for planets which may be able to sustain life.
JWST was designed to operate very far away from Earth (further than the Moon) which means that servicing missions will probably not happen (however plans for sending manned missions to Mars may change this). Hence its best line of defence will be redundancy. The telescope will be over-designed to account for any possible anomaly which may occur during its 5-10 year long mission. Another complication posed by its distant residence and its immense size is the deployment of its instruments. JWST cannot be placed inside its Arriane 5 launch vehicle fully deployed because it simply wouldn't fit. Engineers therefore decided to fold it inside the spacecraft and begin its deployment once it is in outer space (solar panels, antennae, sun shields and secondary + primary mirrors).
We are all well aware of how Hubble managed to change our perception of the Universe since it was launched. It is hoped that the James Web Space Telescope will go beyond Hubble's achievements and embark on a journey which may finally answer age-old questions which continue to elude humankind.