What is the purpose of 'evolved Laser Interferometer Space Antenna (eLISA)' project?

The correct answer is B. eLISA was ESA's planned space-based gravitational wave observatory. Three spacecraft would fly in a triangular formation, with arms several million km long, to pick up low-frequency gravitational waves that ground detectors like LIGO cannot sense. The mission has since been shortened to LISA, and ESA adopted it in 2024 with a launch planned for the mid-2030s.

• A is wrong: Neutrino detection is done by underground or underwater detectors such as Super-Kamiokande and IceCube, not by a space interferometer.
• C is wrong: Missile defence testing has no link to gravitational wave interferometry.
• D is wrong: Solar flare effects on communication are studied through space weather missions such as India's Aditya-L1, which is a solar observatory, not a gravitational wave project.

The core concept is gravitational waves, ripples in spacetime predicted by general relativity and first directly detected by LIGO in 2015. For Mains, this connects to science and technology achievements and to India's own space and fundamental science programmes.

Trap: Aspirants often pick A because the word neutrino sounds like a 'detect particles' project. Read the purpose, not the sci-fi sounding name.