The Immortal Hubble Telescope

src:nasa

NASA, the state space agency of America, has been known worldwide for the awe-striking missions undertaken by it. From exploring planets nearby to the galaxies in the different parts of the universe, nothing's left unexplored by this space giant. NASA has been always striving to push the limits and and set standards in astronomical works. And one among these is the Hubble Space Telescope.

Hubble Space Telescope src:nasa

Hubble Space Telescope is the most prestigious project NASA has ever delivered. The Hubble telescope was launched on 24 April, 1990 with an aim to have a better look of the outside world. Hubble had cost around $1.5 billion but various repair missions have increased the mission's cost to about $2.87 billion.

The Hubble Space Telescope has a long history. Its foundation lies back in 1923 when German scientist Hermann Oberth proposed the need of a telescope in the Earth's orbits. But the time didn't support this ides due to the lack of machinery and technology to do so. So this matter went in abeyance till 1969 when the rocket launchings had become a commonplace thing. And gained its final approval in 1977 when the Congress passed the budget. Finally the NASA and ESA joined hands to make the project successful.

Cassegrain reflector src:wikipedia

The Hubble telescope belongs to a class of Cassegrain reflector. This type of reflector has a primary concave reflector which redirects the light ray entering to a secondary convex mirror. The secondary mirror in turn transfers the light to the main instruments of the Hubble. The instruments like cameras and spectrographs analyse the imagery and transmit it to the collection center on the Earth.

 Hubble telescope contains a set of 4 reaction wheels which control the motion of the telescope. The telescope makes use of the Newton's Third Law of Motion according to which every action has an equal and opposite reaction. In order to turn the telescope to one direction the reaction wheels are rotated by the same amount in the opposite direction. Thus helping the telescope to change direction. The telescope also houses 6 nickel-hydrogen batteries of approx 22 car batteries. These batteries are recharged with the help of 25 foot solar panels and generate a power of 5500W while the usage is only of 2100W. Hubble has a dynamic property of locking onto a target of the thickness of a hair strand from as far as 1 mile without deviating more than 7/10000th of arcsecond.

Parts of Hubble src:nasa

The telescope is 43.5 ft long and 14 ft wide. The telescope has a weight of about 25,000 pounds and is the same in dimension as a school bus. Hubble has been surrounded by thick multi layer insulation which saves it from the extremes of climate experienced by the telescope in its journey round the Earth. The Hubble has been stuffed with various instruments and cameras to get the view of every possible region of the universe. This was also the primary reason for the launch of the telescope. The telescopes on the Earth were efficient but the data collected by them were highly affected by the atmosphere and the weather conditions nearby. While this is not the case with Hubble which rotates round the Earth at the rate of 15 orbits per day. Being placed above the atmosphere helps it in getting an obstruction free view of the vast universe and also in the easy repair of the various parts of the telescope. The telescope gains advantage of being the only serviceable telescope due to the fact that it lies in the low earth orbit while other space telescopes, like Kepler, are placed much far from Earth which makes it difficult to repair them or provide some hardware update in them.

Image obtained before and after correction of lens flaw src:nasa

The telescope launched successfully but its working faced a problem at the initial stages. The problem which turned out in its working was the wrong placement of the lens. This was a major issue as it lead to a decrease in the quality of the image obtained as was expected by the telescope. Though the image quality was much better than that obtained by the telescopes on the ground, it was not of the quality the telescope had been calibrated for. The main cause of the problem was the ill-placement of the lens by about 1.3mm. This had decreased the sharpness of the image and produced spherical aberration. NASA viewed every point for the correctness of the flaw and came to a conclusion of adding another lens of same size but the opposite specs to neutralize the effect and hence sent the first service mission in December 1993. Since then several service missions have been sent for some corrective measures in the telescope.

The Hubble has proved to be the most successful and efficient one for NASA. Since its launch the various achievements of the telescope are-

• Hubble has made more than 1.3 million observations since its launch.
• More than 15,000 scientific papers have been published and these papers have been mentioned more than 738,000 times in other papers.
• Found out the age of the universe, i.e., 13 billion light years old.
• Found out the gas pillars, known as the 'Pillars of Creation', in the Eagle Nebula.

Pillars of Creation src:nasa

• Discovery of new galaxies.
• Discovery of supermassive black holes.

Representative Image of Black Hole src:nasa

• Discovery of exoplanets.

The Hubble has been working flawlessly in the Earth's lower orbit and discovering the treasures of the Universe. The scientists have confirmed that the telescope will work all well till 2020 and probably much longer continuing to serve its purpose.