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The telescope as we know it traces its origins to the Netherlands in the year 1608. The original device consisted of a series of lenses, which astronomers, including Galileo, used in 1609. Later on, the work and research by other scientists and astronomers such as Isaac Newton, Laurent Cassegrain, Chester Moore, and John Hadley made great modifications to the original design which gradually evolved to models we use today. The invention of reflecting mirrors revolutionized the telescope design which made possible creation of the Hubble Space Telescope and many others. On the other hand, modern telescopes appeared in the world at the beginning of the 20th century. The telescopes were made of huge mirrors coated with aluminum and located at remote high-altitude clear sky locations.
The new generation of telescopes includes active and passive optics. Giant telescopes use the principle of active optics by which they are able to measure the distortions due to the motion of turbulence in the Earth’s atmosphere and then make allowance for these factors. Examples of giant telescopes include the two Gemini Telescopes: the Large Binocular Telescope, and the Very Large Telescope (having four separate telescopes) (Schilling & Rarr, 2016). Other forms of telescopes include the Radio telescope, which uses high-energy radio waves, infrared telescopes, ultraviolet telescopes, x-ray telescopes, and gamma-ray telescopes.
Giant Telescopes: Improvements for the future
The improvement and advancement of technology and the adaptive optical principle, such as Multi-conjugated Adaptive Optics, will enable the first generation giant telescopes to advance to the second one. The telescopes will be equipped with a second-generation equipment often performing at the diffraction limit. These future instruments include a multi micro-mirror and the distributed classical Adaptive Optics system instrument also known as the FALCON. These new technologies help observers to study in detail many individual objects in the telescope’s FoV at the same time. Other new additions include Adaptive Optics-fed planet finders using nulling interferometry coronagraphs, NIR multiobject wide-field spectroimagers, image slicer-based multi-integral field spectrographs, and very wide wavelength coverage “fast” shooters, which are able to do simultaneous spectroscopy from 0.3 to 3μm. The “underlying philosophy is one of sampling the instrumentation parameter space (wavelength, resolution, FoV, image quality, multiplex, synergy with other space or ground facilities) based on clear science requirements” (Overbye, 2013).
These new projects are already underway with a great example being the ALMA (Atacama Large Millimeter Array) which is a collaboration between the USA and European Union. The ALMA, which will be managed by AUI and ESO, is based in Chajnantor, the desert of Atacama. Scientists and astronomers have taken different directions in trying to develop these giant telescopes. Improving the current Giant Telescope has been one of the ways to do this when telescopes have become more sensitive to faint bodies not just because of increases in diameter but also because of advances in detector technology. This improvement has also led to other advancements of the next-gen telescopes including its increase in size because of little room for further progress inefficiency. Traditionally, the size of new telescope designs has been limited by the ability to produce the mirror glass, cast it in the necessary shape, and polish it. Polishing these mirrors in the past proved to be rather challenging because the process took a long time. Today’s mirrors are shaped under computer control, greatly accelerating the schedule. The four 8.2-meter VLT mirrors were each polished in one year, with measurements were taken almost continuously.
Advanced optical technology hardly matters if the telescope cannot even support its own weight. The telescope framework needs to be stiff enough to keep the mirrors precisely aligned with one another and to resist vibrations induced by the wind. Therefore, the telescope should adhere to both mechanical and optical rules to meet the necessary requirements. Another potential problem is that as the telescope tracks the heavens, its weight shifts, which can bend the instrument and cause its mirrors to move out of alignment. Therefore, frameworks that closely align the mirrors during movement are designed to be robust.
Larger telescopes are needed because scientific problems, such as the study of extrasolar planets and the building blocks of stars and galaxies, cannot be tackled with inferior instruments. Over the centuries, telescopes have gone from the size of a bedside table to the size of a room, a house, a cathedral, and now a skyscraper. Thanks to the advances in technology, we can build instruments able to see the first stars ever to be born in the universe and planets around other stars, including possibly sister planets of Earth. The “question is no longer whether we can build giant telescopes or why we would want to, but when and how large” (Angel & Gilmozzi, 2003, p. 18).
Extremely Large Telescopes
Giant telescopes of the future include the Extremely Large Telescopes (ELTs). These telescopes are relatively huge when compared to the current telescopes. Currently, ETLs consists of projects that are still being worked on. One of the proposed giant telescopes is the OWL, which has difficulties with segmented mirrors. This design has to be implemented due to the fact that there is no existing machinery that can construct a monolithic 60-100 meter large mirror. The functioning of a segmented mirror is often more complex than that of a monolithic one, which requires the cautious arrangement of the segments (through a method known as cophasing). Knowledge from operations of the existing segmented mirrors project indicates that the OWL project is tenable. Nevertheless, the expected price (of around €1.5 billion) was thought to be too high, so the ESO is now constructing the smaller ‘European Extremely Large Telescope’, which is around thirty-nine meters in width.
Examples of these projects include “a 20-meter Next-Generation Canada-France-Hawaii Telescope (ngCFHT) which is a project by the Canadian, French, and Hawaiian astronomers, the 20-meter Super-Subaru project by the National Observatory of Japan (NAOJ), and the 25-meter version of the Hobby-Eberly Telescope in Texas” (Schilling & Rarr, 2016). The proposed 30-meter California Extremely Large Telescope (CELT) is a collaboration between various universities. Another example of a future proposed giant telescope is the Segmented Mirror Telescope (GSMT) and it is set to be built by the Association of Universities for Research in Astronomy. These two entities have since resolved to combine efforts and design the Thirty Meter Telescope (TMT). This project also involves a group of researchers from Canada.
In Europe, projects such as Opticon (Optical Infrared Coordination Network) are being funded to build ETLs such as those in the USA. Examples of these projects are “the Swedish-led Euro50 project (a 50-meter segmented-mirror telescope to be built in the Canary Islands) and the 100-meter Overwhelmingly Large (OWL) telescope designed by the European Southern Observatory” (Gilmozzi, 2006, p. 65).
There is no better place to position a telescope than space itself, and this served as a foundation for another entirely new approach for the development of the telescope. Unlike ground telescopes, “above the earth’s atmosphere observations are no longer hampered by air turbulence, so telescopic images of distant stars and galaxies are relatively well-focused” (Schilling & Rarr, 2016). The telescope has the ability to record certain types of radiations that are absorbed by the atmosphere, let alone it can take pictures of the best view of the universe. Depending on the position on the orbit the telescope is situated, it can be serviced or upgraded.
According to experts, “such a telescope would be big enough to find and study the dozens of Earth-like planets in our neighborhood and it could resolve objects only 300 light-years in diameter anywhere in the observable universe” (Overbye, 2013). The Hubble has been the stepping-stone for all other orbital telescopes. Eventually, these telescopes will help astronomers in exploring whether there are other habitable planets in the universe. The biggest technical problem for future giant telescopes is suppressing the glare from stars when attempting to find their planets. The sun, for example, is 10 billion times brighter than the Earth. The future “space telescope would be equipped with an internal coronagraph, a disk that blocks light from the central star, making a dim planet more visible, and perhaps eventually a starshade that would float miles out in front of it to do the same thing” (Overbye, 2013).
Designers of the next generation telescopes, including ELTs, try to break one or both of the traditional laws of the art of telescope making: the cost law and the growth law. This is because these telescopes are very expensive and some projects may not succeed. For example, investing in light-suppression technology now might prevent the cost overruns that led to the Webb telescope’s nearly being canceled just a few years after the project had been proposed. On the other hand, visible and near-infrared light ground-based telescopes offer higher resolution and sensitivity at a lower cost than orbital observatories. Other factors that affect the success of the future telescopes include; the sensitivity of the telescope and their resolution, the atmosphere (which hinders the accuracy of the ground-based telescope), site selection, the wind, and the different instruments in the telescope.
The telescope was once the greatest scientific discovery of the time. However, since Galileo conceptualized the telescope and its importance in learning about heavenly bodies, scientists have worked hard to develop this original concept. Currently, the issue with telescopes is not what they can observe in the heavens, but also what they can ‘listen to’ in space. Consequently, future giant telescopes are needed to investigate the challenges that the current inventions in space exploration and ground-telescopes have brought. The success story of future giant telescopes depends on a number of factors including cost and innovation capacity. For these projects to be successful, their funding should be greatly encouraged. Several stakeholders have come together to pursue the dream of giant telescopes making this venture a global affair. Currently, telescopes are recognized for their ability to expedite retrieving the ultimate knowledge of other galaxies and their formations. Unlike a few years ago, there is a likelihood of a new era of future giant telescopes being witnessed in just a short period of time.
Angel, J. & Gilmozzi, R. (2003). Future giant telescopes (1st ed.). Washington, D.C: Society of Photo-optical Instrumentation Engineers.
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Gilmozzi, R. (2006). Giant telescopes of the future. Scientific American, 294(5), 64-71.