Sunday, June 7, 2009

Hubble Space Telescope

-By Rishi Shah & Sudeep Neupane

The Hubble Space Telescope (HST) is one of the largest and marvelously versatile iconic space telescopes, which has been designed for observing and probing the wonders and mysteries of the universe. It was put into near-circular low earth orbit by Space Shuttle Discovery in April 1990. It weighs fairly eleven thousand kilograms and revolves around the earth in merely ninety seven minutes from safe orbital height of modest six hundred kilometers. Its mirror measures barely 2.4 meters in diameter. HST is a collaborative project between NASA and European Space Agency (ESA). It is named after the famed American astronomer Edwin Hubble (1889-1953) who introduced the confounding concept of expanding universe. HST is one of NASA's series of four Great Observatories satellites that include Compton Gamma Ray (already decommissioned) and Chandra X-Ray Observatories and Spitzer Space Telescope that with almost similar size and outset outlay are responsible for examining cosmic objects in specifically assigned electromagnetic spectrum.

Though space telescopes were proposed in 1923, the advantages of diversely instrumented space observatory over ground-based telescopes were being explicitly realized. They could peer at celestial entities in infrared and ultraviolet light unhindered by the atmosphere and with better resolution. In 1966 NASA lofted the first ill-fated Orbiting Astronomical Observatory (OAO) but its battery failed after three days. It was followed by OAO-2, which executed ultraviolet inspections of stars and galaxies after its lift-off in 1968 until 1972. After long and wearisome nationwide lobbying effort by scientific community, US Congress eventually approved incipient funding of thirty six million US Dollars in 1978 for contriving Large Space Telescope (LST) that was later dubbed Hubble Space Telescope. ESA agreed to fund and supply first generation instruments as well as solar cells along with professional staff for HST in return for European astronomers being guaranteed at least fifteen percent of the observing time on the telescope. After confronting technical delays, budget over-runs and the unforgettably saddening disaster of Space Shuttle Challenger, HST was thrillingly launched into space. But soon thereafter the experts realized that the images it had taken were blurry and indistinct. It was found out that its main mirror of HST had been ground incorrectly to wrong shape. Clever solution for rectifying this serious problem was carried out by first servicing mission in 1993 by well trained astronauts in Space Shuttle Endeavour, who restored HST’s vision to intended superior level. HST is the only telescope to be serviced in space by astronauts for assuring its flawless performance. Five missions to repair and refurbish various subsystems and replace the old instruments with modern and capable versions were envisaged. After the fatal misfortune of Columbia Space Shuttle in 2003, the fifth and final servicing mission in Space Shuttle Atlantis has rejuvenated HST recently to enable it to be scientifically more functional till 2014, when its more sophisticated successor, James Webb Space Telescope (JWST), would spring into operation. As JWST (named after NASA's second administrator, James E. Webb) would only scrutinize in infrared spectrum, it would complement and not substitute Hubble's ability to watch extensively in visible and ultraviolet wavelengths ESA has also ambitiously sent Hershel Space Observatory and Planck Telescope currently into space. ESA’s Herschel Space Observatory would collect light from objects dwelling in our Solar System and in our galaxy the Milky Way and even from extragalactic bodies that are billions of light-years away as from newborn galaxies. It would primarily investigate star formation in galaxies, composition of possible atmospheres of Solar System bodies and molecular chemistry across the universe. It is named after German-born British astronomer Sir William Herschel (1738-1822) who discovered infrared spectrum and planet Uranus. Planck Telescope would witness so-called anisotropies of the cosmic microwave background (CMB) over the entire sky. It is named in honour of famous German scientist Max Planck (1858–1947). It would attempt to add information that could address cosmological and astrophysical issues. If not re-boosted properly HST would slowly re-enter earth’s atmosphere by 2032 and burn-up. Since some surviving remnants would still fall on earth’s surface, HST would probably be permitted to meet its fiery end in controlled manner over open sea or over unpopulated area to avoid any material damage and human fatalities. As Space Shuttles would be retired from service in 2010 and human space flight missions would be conducted with Orion Spacecraft, astronauts would perhaps visit HST for de-orbiting it in future in this new craft.

HST has contributed to mind-boggling discoveries in astrophysics and resolved numerous long-standing problems. Its results have required new theories for solving and apprehending them. It measured distances to Cepheid variable stars in Virgo Cluster more accurately and attempted to constrain the value of conventional Hubble Constant that expresses expansion rate of the universe. Hubble's commanding position outside the earth's atmosphere allows it to take extremely sharp images. Ultra Deep Field photos of high resolution are exceptionally detailed. They exhibit most afar embodiments billions of light-years away gloriously and bestow us with opportunities to discern our early universe. These remarkable pictures have suggested the prevalence of baffling black holes in the nuclei of nearby galaxies. The rare collision of Comet Shoemaker-Levy9 with Jupiter in 1994 was fascinatingly captured and displayed by HST. Experts could peruse arcane dynamics of such rare impact of comet with a planet. HST revealed Proto-planetary disks (so-called proplyds) in the Orion Nebula with possible evidence for the presence of extra solar planets (exo-planets) around sun-like stars. It has also recorded many intriguingly enigmatic Gamma Ray Bursts (GRBs). HST has analyzed far-flung dwarf planets like Pluto and Eris that inhabit the outer realms of our Solar System and promoted the understanding of our cosmos and its expansion in accordance with Hubble’s Law that states that velocity of galaxies receding from the earth is proportional to their distance from us and supports the hypothetical Big Bang Model which describes the initial conditions and subsequent development of our universe that arguably began fairly 13.7 billion years ago.
HST is considered the bastion of international cooperation in astronomy. Anyone can apply for time on HST for astronomical research due to absence of restrictions on nationality or academic affiliation. Calls for proposals are issued annually for time allocation as needed for research purpose by avid scholars. Furthermore, astronomers globally can apply to use designated Director's Discretionary (DD) Time, which is typically awarded for study of unexpected transient phenomena such as supernovae (colossal star explosion). The Space Telescope Science Institute (STScI) in Baltimore, USA is in-charge of scientific activities and delivery of data to astronomers worldwide. The Space Telescope European Coordinating Facility (ST-ECF), in Garching near Munich in Southern Germany, provides similar support for mostly European astronomers. Although HST’s cumulative escalated financial cost could have reached questionably now up to circa ten billion US Dollars in addition to ESA’s contribution of roughly six hundred million EURO, HST has furnished invaluable information to the quest for knowledge for comprehending the universe, our origin and our eventual fate on blue planet earth.
( This article was published on in The Rising Nepal,National English Daily on May 23,2009)

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