UPSC Prelims 2020 Question:

The experiment will employ a trio of spacecraft flying in formation in the shape of an equilateral triangle that has sides one million kilometers long, with lasers shining between the craft." The experiment in question refers to

Explanation:

• With the second detection of gravitational waves by the Laser Interferometric Gravitational-wave Observatory (LIGO) detector, the space for experimental research on black holes using gravitational waves expanded.
  
  
• Laser Interferometer Space Antenna (LISA) is a laser interferometric gravitational wave observatory in space with 3 spacecraft in heliocentric orbit and million km arm length. An evolving LISA concept is being developed by the Evolved LISA (eLISA) Consortium.
  
  
• eLISA is a plan of setting into space three spacecraft, a mother and two daughter spacecraft, which will fly in a triangular formation. Each arm of the imaginary triangle, from the mother to each daughter spacecraft, will measure about a million km. Inside these spacecraft will float ‘freely falling’ test mass cubes. Laser interferometers will accurately measure any minute changes in the distance between these cubes due to gravitational waves. It is expected to be launched in 2037.
  
  

Therefore, option (4) is the correct answer.

Subject: Science & Technology | Space and Related Developments