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Eye on solar cycles, Isro to work on shielding telecom satellites

Eye on solar cycles, Isro to work on shielding telecom satellites
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First Published: Tue, May 15 2007. 12 33 AM IST
Updated: Tue, May 15 2007. 12 33 AM IST
New Delhi/Bangalore: A debate on whether the peak of the current solar cycle due in 2011 will be weak or strong, fuelled in part by a recent paper by an Indian scientist who argues that it will be weak, could decide on the kind of protective shields the Indian Space Research Organization (Isro) needs to provide communication satellites that it plans to launch between now and then.
Solar cycles are periodic variations of the number of ‘sunspots’, which are cool, dark patches on the sun’s surface. These spots peak every 11 years, the most recent being in 2000. When such spots peak in a solar cycle, the sun spews out jets of plasma and charged particles that, in turn, can cause violent magnetic storms that play havoc with satellite transmission.
In perhaps an indication of things to come, on 2 January, data services delivered on an Indian satellite, INSAT-4A, were disrupted for about half an hour in the late afternoon when solar disturbances switched off one of the momentum wheels used in stabilizing the spacecraft. Isro engineers set the bug right, but the incident drove home the strength of solar cycles.
Heavy users of satellite-based data services, such as the National Stock Exchange (NSE) of India, which has over 3,000 ‘very small aperture terminals’ (VSATs) used for share trading spread over the country, were concerned, too, about how the 2011 peak of the solar cycle would affect their operations. As it is, for about 10 days each in March and September every year, both NSE and the Bombay Stock Exchange reschedule their trading hours on account of strong electromagnetic waves in space on account of ‘equinox’, the period when the sun is directly above the earth’s equator. These waves disturb data transfer through VSATs.
In a recent paper in ‘Physical Review Letters’, an American peer-reviewed journal, Arnab Rai Choudhuri, a scientist at the Indian Institute of Science in Bangalore, forecast that the upcoming solar cycle—called Cycle 24—will be one of the weakest in the last hundred years, contrary to international predictions last year that it would be one of the most intense cycles.
If Choudhuri is right, Isro engineers designing communication satellites to blast off between 2010-2012 can breathe easy. If the scale of sunspot activity is high, scientists on ground will have just a few hours to study and react to resultant high energy particle releases or plasma eruptions, said P. Venkatakrishnan, head of the Udaipur Solar Observatory, a unit of Physical Research Laboratories, the research arm of the department of space. But if they are less intense, he said, the high energy releases will take 40-80 hours to reach earth, giving adequate time for the satellites to take evasive action.
Isro has 11 communication satellites in service, of which one, INSAT-2E, would have finished its life cycle by 2011. Another seven communication satellites that would help in satellite television broadcasting and serve telecom service providers are to be placed in space 36,000km above the earth by then. The space agency’s spokesman S. Krishnamurthy, declined to comment on Isro’s preparations for the 2011 peak of the solar cycle, but said its communication satellites that usually have a life of not more than 17 years are shielded with a special paint that can last through sunspots and flares on one solar cycle.
Even so, space scientists and astrophysicists in India have taken note of two predictions for the 2011 sunspot activity by US scientists, who have forecast record highs, attracting considerable attention. David Hathaway of National Aeronautics and Space Administration’s Marshall Space Flight Centre at Huntsville, Alabama, had in December 2006 said he expects “one of the most intense solar peaks in 400 years” in 2011. His conclusion is based on records of geo-magnetic storms. Around the same time, Mausumi Dikpati at Boulder, Colorado’s National Centre for Atmospheric Research, predicted with a non-empiricial, theoretical computer model, that the 2011 sunspot cycle would have an extremely strong peak—one of the highest in 50 years.
It is not just satellite services, which facilitate everything from data transfer to communication to navigation (especially for ships), that are potentially at the mercy of solar cycles. Researchers in India have tried to correlate sunspot activity with the monsoon rains, which irrigate over nine-tenths of the summer rice crop in India. K.M. Hiremath, a scientist at the Indian Institute of Astrophysics, Bangalore, used 130 years of data and showed last year that annual rainfall is higher during periods of low sunspot activity. The converse—that high sunspot activity causes lower rainfall—has not been conclusively proven but it could be possible, he admitted. A rainfall prediction model used by S.T.G. Raghukanth of the Indian Institute of Technology (IIT), Guwahati, which predicted rainfall activity 11 out of 14 times in a Karnataka district, uses sunspot activity as a key variable.
An Indian scientist said he would back the estimate of the Indian Institute of Science’s Choudhuri, who has predicted that the sunspot activity will be 35% lower than the previous peak in 2000. “I am inclined to swing in Choudhuri’s side,” said Rajan Bakshi, an astrophysicist at the IIT, Delhi. “That’s because forecast models are way too unstable and Choudhuri’s results match historical data... I think he has a strong case,” he added.
jacob.k@livemint.com
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First Published: Tue, May 15 2007. 12 33 AM IST
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