The Prime Minister Dr Manmohan Singh has called for liberating Indian science from the shackles of bureaucracy and in-house favouritism.Advocating the need for greater autonomy for scientific institutions, he regretted that red tape, political interference and lack of proper recognition of good work has led to regression in Indian science in some sectors.The Prime Minister said, special effort must be made to encourage scientists of Indian origin currently working abroad to return to India.Inaugurating the 97th Indian Science Congress in Thiruvanthapuram, he called for special incentives to turn brain drain into brain gain for the future.He also pointed to the challenges before the scientific community on the front of food and energy security and climate change mitigation.Dr. Manmohan Singh said India must achieve energy efficiency and shift to renewable energy. He underlined the need for a plan for accelerated nuclear power. Referring to the Copenhagen summit on climate change, the Prime Minister said there was a limited success as nobody was satisfied with the outcome.Speaking on the sidelines of the Congress, India's top Defence Scientist said that a weapons system is being readied to neutralise enemy satellites operating in low-earth orbit.Defence Research and Development Organisation Director General V K Saraswat told reporters that India is putting together building blocks of technology that could be used to neutralise enemy satellites.He however added that the defence scientists have not planned any tests but have started planning such technology which could be used to leapfrog to build a weapon in case the country needed it.