As the millennium draws to a close, an extraordinary sure of creative energy is coursing through the astronomy community, Not since 1610, when Galileo tntincd his primitive spyglass on Jupiter, have astronomers witnessed such a fertile renaissance of technical Innovation and scientific discovery.
With gigantic ground: based telescopes and sophisticated orbiting Observatories, scientists are exploring the cosmos at nearly every wavelength of the spectrum. Their discoveries have been nothing less than sterling and reveal in exquisite detail a universe of unimaginable violence and complexity.
‘The pace of discovery is breath: taking, as capabilities advance by orders of magnitude and variety of ‘Breakthroughs blaze the trail lo ward further discovery, The most important accomplishments have ‘been the advent and continued development of CCD (charge: coupled device) imaging arrays for sensitive detection, very large telescope mirrors for unprecedented light gathering power and Angular resolution, adaptive op: tics to compensate for atmospheric turbulence, and space based platforms that can complicacy escape earth and its air.
Many of these technologic are embodied in a single colossal telescope located on the summit of an extinct volcano ML Mauna Kea above the island of Hawaii. Almost everything about the Keck is big. It is the largest telescope in the world, with a primary mirror spanning 1O meters. It gathers four times more light than the Hale telescope, yet weighs the same about 15 tons. With that kind of light gathering power, astronomers hope to probe as far as 14 billion light years into space. And in April, 1993, Keck astronomy captured an image of the most distant known galaxy (4C41.17) some 12 billion light years away. ‘The galaxy was caught by one of Keck’s first light instruments, the near IR camera (NICR) consisting of state~ of the CCD imaging arrays.
The Keck is just one of many large telescopes that will see first light this decade, By the Carty 21st century, about 10 8meicr class icescapes will dot the globe. Just a stone’s throw away from Keck on Mauna Kea, the National Observatory of Japan is building an 8 meter telescope for the 0.3 to 30 micrometer special region. Scheduled for completion in 1999, the Subarea icescape will feature a new concept in primary mirror design.
First light instruments for the Subarea are still under consideration, but one intriguing design, the infrared mosaic camera, would use 4 mosaic of 64 1000 * 1000 CCD arrays for wide field sky Surveys. Other proposed instruments include a chronograph imager with adaptive optics, an IR camer and spectrograph and an OH airglow suppressor.
One of the most ambitious telescope projects under construction is the European Southern Observatory ESO very large Telescope ‘(VLT) in the high, dry mountains ‘of Chile. When completed, the VLT will comprise four8M icescapes operating as. One to synodic Size he light gathering power of a single 16m mirror with 10 times the area of the Hale Telescope. Many of the large new generation telescopes include plans for adaptive optics. In the visible and radio ‘way Neigh portions of the spectrum, where ground based astronomy is traditionally done, the deras relatively transparent. But at IR wavelength, atmospheric transmission resembles a picket fence and everything, including the telescope, glows like a hot plate. Worse yel. our atmosphere looks like a brick wall at far IR extreme ultra violet (EUV), X ray and Gamma ray wavelength, ‘The most effective way to compensate for atmospheric absorption and distortion is to rise above it, and the only way to do that is to drag instruments aloft on a balloon, sounding rocket or space based platform. It is costly and risky, but the potential rewards are alluring. Orbiting observatories such as ROSAT, Infrared astronomical satellite (RIS) and Hubble space telescope (HST) have revolutionized our understanding of the universe. And a cornucopia of future space based observations could dwarf these discoveries.
The importance of IR spectra to astronomy was driven home by the dramatic discoveries made by the IRIS; in 1985 the IRIS surveyed the entire sky at 12, 25, 60 and 100 um and uncovered scores of exotic objects. Including large number of distant galaxies so obscured by dust that they can only be seen in the IR.
From these and other IR discoveries has sprung the new frontier of IR astronomy, a field that owes much to the development of IR detectors and CCD imaging arrays, The CCD which first appeared in 1970 already has earned a reputation in ground based visible astronomy by boosting greater efficiencies far beyond the paltry 2 percent of photographic film to the incredible 80 percent of some modem CCDs… Now (he spectacular gains once made in the visible are reaching into the IR. Two important missions planned for launch this decade hope to parity these new IR technologic into another great Leap in our knowledge of the universe: the infrared space observatory (ISO) and space IR telescope exploratory (SIRTE).
These missions offer just a taste of the many breathtaking advances that continue to inspire astronomers. When Galileo first peeped through his crude 2in. Refractor, what he saw changed forever our view of the universe and ourselves. And as astronomy ventures forth into a new car of discovery, the view from earth just keeps on getting better.
(By H.S. Jattana, The author is Manager (VLSI) with Semiconductor Complex.)
Article extracted from this publication >> September 9, 1994
