UPSC Prelims 2020 · GS Paper I
Question 43: Science and Technology
“The experiment will employ a trio of spacecraft flying in formation in the shape of an equilateral triangle that has sides one million kilometres long, with lasers shining between the craft.” The experiment in question refers to
AnswerUPSC’s answer is (d).
Three spacecraft flying in an equilateral triangle with arms of one million km, linked by lasers, describes the Evolved Laser Interferometer Space Antenna (eLISA), a planned space detector of gravitational waves. LISA Pathfinder (2015 to 2017) only tested the technology with a single craft, while Voyager-2 and New Horizons are deep-space probes.
Why each option is right or wrong
- (a) Wrong: Voyager-2 is a single probe sent to the outer planets.
- (b) Wrong: New Horizons is a single probe that flew past Pluto.
- (c) Wrong: LISA Pathfinder tested the technology and was not a triangle of spacecraft.
- (d) Right: eLISA is the planned triangle of spacecraft with laser links.
Worth knowing: The mission has since been redesigned and is now called LISA, with arms of 2.5 million km; UPSC's answer rests on the earlier eLISA design with one-million-km arms.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2020, General Studies Paper I, Series A. The paper on upsc.gov.in.