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Strides in satellite technology UNDERSTANDING THE UNIVERSE
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Strides in satellite technology
Indian space programme which completed 40 years in November 2003, has made rapid strides in designing and developing state-of-the-art spacecraft for a variety of applications and utilising them for the socioeconomic development of the country. The expertise built up by the Indian Space Research organisation (ISRO) in building satellite systems for a wide ranging uses has been recognised the world over. And key to the social philosophy of ISRO — exploitation of space technology for nation building — lies in the INSAT and IRS network of satellites. First about the INSAT or the Indian National Satellite which has been described as the “largest domestic communication satellite system in the Asia Pacific region”
Till now, the fully Indian made INSAT series of satellites used to be launched by means of the European Ariane range of boosters, because India lacked an operational launch vehicle capable of accomplishing a mission to the
geostationary transfer orbit. INSAT-3E, ISRO’s latest satellites was launched in September 2003, by means of an Ariane-5 booster. However INSAT-3D, a dedicated weather watch satellite, will be launched at the head of Indian made
Geosynchronous Satellite Launch Vehicle (GSLV) in 2005. Commissioned in 1983, the INSAT system today provides more than 130 transponders in various bands in addition to demonstrating its meteorological earth observation capability. The services made available by INSAT include telecommunications, TV broadcasting, weather monitoring, disaster warning and satellite aided search and rescue operations. India continues to harness the INSAT system capability to support the Gramsat communications network at various levels to provide computer connectivity, data and TV broadcasting for applications in e-governance and distance learning, teleconferencing, and disaster management. Parallelly, INSAT system has helped expand the scope of health services through the setting up of telemedicine networks in various parts of the country. These networks enable specialised medical facility to be available in the remote parts of the country. INSAT system capability has also been used for demonstrating and introducing innovative communications services, including satellite based aircraft navigation system., mobile communications, digital audio and data broadcast services and emergency communications services. The launch of the exclusive weather watch satellite Kalpana-I in Sept, 2002, by means of the four-stage Polar Satellite Launch Vehicle (PSLV) provided a fillip to INSAT meteorological services. Meanwhile, the mid-2004 would witness the launch of G-sat-3 satellite for education that would cater to the language specific, culture specific and region specific interactive education — at the head of a GSLV booster. It will carry five Ku-band transponders to provide coverage through five regional beams. The G-Sat-4 experimental communications satellite planned to be launched in 2005 also be means of GSLV will carry an Israeli built telescope to scan the ultraviolet sky and solve some of the riddles surrounding star formation, history of galaxies and physics of the black holes. ISRO has also taken up a project to develop an advanced communications technology satellite to demonstrate advanced communications techniques and technologies for the future generation INSAT system. The fourth generation INSAT system comprising as many as seven satellites is expected to boost the availability of transponders over the Indian skies to a substantial extent. The Satellite Centre of ISRO in Bangalore has covered much ground in the development of INSAT-4A and INSAT-4B satellites. In the area of satellite based remote sensing India claims to operate the world’s largest constellation of remote sensing satellites. The IRS (Indian Remote Sensing Satellite) system commissioned in 1988 today comprises IRS-1C, IRS-1D, IRS-P3, IRSP4, TES and IRS-P6. According to the sources in the Indian Space Dept, “the system provides space based remote sensing data in a variety of spectral, spatial and temporal resolutions meeting the needs of many applications of relevance to national development.” Data from IRS constitutes the mainstay of the National Natural Resources Management System (NNRMS), which is an integrated resources management system. India continues to make use of the IRS data for several applications, including forecasting agricultural yield, water resources management, drought monitoring, flood mapping, snow melt runoff prediction, urban developmental mineral prospecting, and environmental monitoring. IRS-P6 or Resourcesat launched by ISRO. This 1360-kg satellite features a high resolution multi spectral camera with across track steerability, providing 5.8-m spectral resolution, a multispectral camera providing 23.5-m spatial resolution in four spectral bands and an Advanced Wide Field Sensor with a spatial resolution of 5.8m. Resourcesat data will help in boosting the service capability in the areas of agriculture, disaster management and land and water resources management. Meanwhile, ISRO is preparing for the launch of IRS-P5 satellite meant for advanced cartographic applications sometime this year. Also called Cartosat-2, IRS-P5 will have two panchromatic cameras with a spatial resolution of 2.5m and a swath of 30-km each. The data products of the satellite will be used for cartographic applications. Cartosat-2 an advanced remote sensing satellite with a single panchromatic camera capable of providing scene specific spot imageries, will be launched in 2005.Further into the future, in 2006 ISRO plans to launch an active microwave remote sensing satellite RISAT or radar imaging satellite carrying a synthetic aperture radar that would allow it to sense the earth both during day and night and also under the cover of cloud and dust. Megha Tropiques, a joint Indo French satellite to be launched in 2006 by means of PSLV sands out as a shining example of India’s commitment to international cooperation in space. The project involves the joint development of scientific instruments to be placed on the French Proteus space platform for the study of tropical atmosphere and events related to aspects such as monsoon and cyclones. |
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UNDERSTANDING THE UNIVERSE Why does it always rain in drops and not like water flowing out of a big This is a beautiful question. I am sure you would agree that it would be a bit unpleasant if a torrent of water were to descend on us unexpectedly in the middle of the night as rain often does. As you know, rain is made up of moisture that is evaporated from large bodies of water. The amount of water vapour in the atmosphere increases when the water bodies are hot. Moisture laden air moves towards land when it becomes hotter than the sea. When this air rises, say by going over a mountain, it cools. Cool air cannot hold as much vapour as hot air. Therefore the vapour condenses into clouds. Clouds are made up of tiny drops of water suspended in the air. An upward motion of the clouds cools them and the tiny droplets join each other to become bigger. Sometimes these droplets freeze into tiny crystals of ice. Large drops and ice crystals become too heavy to float around in the atmosphere. They start descending. In our part of the world the ice crystals melt and the water droplets get bigger while coming down. But they come down only as drops and not torrents of water as if a tap had been opened. Various parts of the cloud do not act in unison while rising up to colder regions. No air mass is capable of suddenly removing all the heat from the vapour in the atmosphere to turn it into a lake of liquid water that might fall or flow onto the earth as a river. Incidentally, even if there were a large tank of water very high in the atmosphere and a tap was used to bring a stream down to the earth the result would be a thick shower and not a steady connected stream. Just try it by opening the tap of a water jug held over the ledge of a roof. Here I will not go into the explanation for breaking up of the stream while descending. The fact that cool air cannot hold as much moisture as hot air is easily proved by a simple experiment. Put some ice in a metal glass and leave it on the table. After some time you would notice that the glass is wet on the outside. This is due to the moisture that warm air has shed on being cooled by touching the cold glass. Is there any possibility for cutting the magnetic lines of force of earth's magnetic field to produce electricity using electromagnetic induction? Theoretically speaking that is possible, but in practice it does not look like a profitable project. One does use the knowledge of the magnetosphere for orienting space vehicles, even for manoeuvring them; magnetic lines of force are used more as pivots and fences to effect changes in direction or orientation of the vehicle rather than sources of energy. These uses do depend on devices that use electromagnetic interaction with the known highways of the earth magnetic field. Practical generation of power might need very large structures, because, even though large in its spread, the strength of the magnetic field is rather low. During rainy weather, the inner surface of the front glass of a moving car gets fogged. What is the reason for this nuisance? When it rains the humidity of the air becomes very high. That by itself would not lead to deposition of fog on the inside surface of the windshield if we kept the windows open. But what is the point of using a car if we are going to get wet. So we roll up the windows. In a non airconditioned car the inside gets warmer than the outside, in addition to the increase of humidity through the sheer biological presence inside the car. The coolest place in the car is the windshield or other window-glasses exposed to the cooler air outside. The moisture in the saturated air in the car therefore begins to condense on these glass surfaces and makes driving quite hazardous. This can be mitigated if we can open the windows partly, and/or have a defroster to heat up the windshield in the front and the back window. |
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Magnetic reversal due to sunstorms
Every 11 years, the sun reaches a peak in its turbulent activity, sporting huge numbers of sunspots and hurling many billion-tonne clouds of charged particles into space. At about the same time, the sun's magnetic poles flip: North becomes south, and south becomes north. Solar physicists have had scant clues about why this switch happens, but a new study suggests that the clouds, known as coronal mass ejections (CMEs), play a central role. By prying loose magnetic-field loops anchored to the visible solar surface, coronal mass ejections may sweep the surface clean of old magnetic fields and prepare the sun for its magnetic reversal. The gradual process requires more than 1,000 CMEs erupting from the polar regions over several years, notes study coauthor Nat Gopalswamy of NASA's Goddard Space Flight Center in Greenbelt, Md. "When it's all over, the sun's magnetic stripes run in the opposite direction," Gopalswamy says. Spider DNA to
control pests DNA found in a spider's stomach could herald a breakthrough in the fight against farm pests, which cause millions of dollars of damage to crops. Cardiff University, UK, scientists, led by Dr Bill Symondson in the School of Biosciences, have become the first to use DNA-based techniques to analyse the content of spiders' guts to identify the prey they have eaten in the field. Money spiders — or Linyphiidae — are a vital controller of pest numbers on farms because their prey includes aphids. However, aphids have poor nutritional value and are sometimes toxic, so the spiders need to balance their diet with other prey. In a field experiment, the Cardiff team's analysis showed that the money spiders were eating large numbers of small insects called springtails or Collembola. Stomach contents showed that they were eating several different species of Collembola, but with strong preferences - DNA from a species, which was uncommon at the site where they were collected, proved to be present most frequently in the stomachs of the spiders. "The DNA analysis enables us to identify precisely what the spiders have eaten," said Dr Symondson. "If we compare that with the prey populations in the field, we can see which prey the spiders prefer to eat when they have a choice."
Infrasonic
symphony Otherwise, they’d be bombarded by the constant din of wind, the intermittent groaning of earth, and the occasional distant explosion. But scientists are eavesdropping on volcanoes, avalanches, earthquakes, and meteorites to discern these phenomena’s infrasound signatures and see what new information infrasound might reveal. Just as seismic waves travel through earth, infrasonic waves travel through the air. And the lower the frequency of the waves, the farther they can travel without losing strength. Scientists first detected infrasound in 1883, when the eruption of the Krakatoa volcano in Indonesia sent inaudible sound waves careening around the world, affecting barometric readings.
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WITH PROF YASH PAL
“Let me start off with a riddle,” says NASA scientist Allan J. Zuckerwar. In his office in Hampton, Va., he rattles off items as dissimilar as rhinoceroses, supersonic aircraft, and hurricanes. “Now, what do they have in common?” The answer, Zuckerwar explains, is that each one generates silent infrasound—long sound waves at a frequency below 20 hertz. People can’t hear anything below that frequency, probably for good reason.