UPSC Prelims 2017 question on Elisa Gravitational Waves

Analysis

The evolved Laser Interferometer Space Antenna plans three spacecraft, a mother and two daughters, flying in triangular formation and trailing the Earth in its orbit around the Sun at a separation of millions of kilometres. Laser interferometers measure minute changes in the distance between test masses in those spacecraft, and a passing gravitational wave produces exactly such a change. Neutrino detection requires large volumes of dense matter rather than interferometry, and neither missile defence nor solar flare research uses this architecture.