Question map
"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
Explanation
The correct answer is Option 4: Evolved LISA (eLISA). This mission, led by the European Space Agency (ESA), is designed to detect gravitational waves from space.
- Why Option 4 is correct: eLISA involves three spacecraft arranged in a massive equilateral triangle formation with sides approximately one million kilometers long. These craft will exchange laser beams to measure minute changes in distance caused by passing gravitational waves, acting as a giant space-based interferometer.
- Why other options are incorrect:
- Voyager-2 and New Horizons are deep-space probes designed for planetary exploration (outer planets and Pluto), not formation flying for wave detection.
- LISA Pathfinder was a successful technology demonstrator mission using a single spacecraft to test the feasibility of the instruments; it did not involve the three-craft triangular formation described.
Thus, the specific configuration of a million-kilometer triangle using laser interferometry uniquely identifies the Evolved LISA mission.
PROVENANCE & STUDY PATTERN
Guest previewThis question rides the wave of the 2015 Gravitational Wave discovery (LIGO). It tests if you know the 'next big step' in that field. It is a classic 'Mission Architecture' questionâUPSC didn't ask *what* it studies, but *how* it looks physically (triangle, lasers). Fair for anyone tracking major global science projects.
This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.
- Statement 1: Is Voyager-2 the experiment that will employ a trio of spacecraft flying in formation as an equilateral triangle with sides one million kilometres long and lasers shining between the craft?
- Statement 2: Is New Horizons the experiment that will employ a trio of spacecraft flying in formation as an equilateral triangle with sides one million kilometres long and lasers shining between the craft?
- Statement 3: Is LISA Pathfinder the experiment that will employ a trio of spacecraft flying in formation as an equilateral triangle with sides one million kilometres long and lasers shining between the craft?
- Statement 4: Is Evolved LISA the experiment that will employ a trio of spacecraft flying in formation as an equilateral triangle with sides one million kilometres long and lasers shining between the craft?
- Describes the Laser Interferometer Space Antenna (LISA) as three spacecraft forming an equilateral triangle.
- Specifies side length in the passage as millions of kilometres (5 million km), showing the multiâmillionâkm scale of the experiment the statement refers to.
- States the configuration uses interferometers operated with infrared laser beams â i.e., lasers shining between the spacecraft.
- Gives the inter-spacecraft distances as 5Ă10^9 m (5 million km), confirming the multiâmillionâkilometre baselines.
Describes Voyager probes as individual deep-space spacecraft that communicate with NASA's Deep Space Network, implying single-probe operations rather than a planned multi-spacecraft formation experiment.
A student could combine this with the basic fact that formation missions usually involve purpose-built, contemporary small spacecraft, to doubt that a 1977 probe like Voyager-2 is part of a new triangular laser-formation experiment.
Gives Voyager/other probe launch dates, mission objectives and current distances (AU), showing Voyager is a long-travel single probe with a decades-old mission profile.
Using a world/solar map and those distances, a student could judge the practicality and likelihood of re-tasking an ageing, solitary interstellar probe into a coordinated threeâcraft laser formation with million-kilometre baselines.
Explains simple laboratory use of lasers and safety, showing lasers are terrestrial experimental tools and used under controlled supervision â not evidence of spaceborne millionâkm laser links but establishes what 'laser experiment' entails.
A student can combine this with standard knowledge that space lasers for inter-spacecraft links require specialized hardware and planning, making it plausible to question whether Voyager-2 (a 1970s probe) would host such a system.
Contains a clear visual/example of a triangle used in a historical mathematical/diagrammatic context, providing a simple geometric reference for 'equilateral triangle formation' as a conceptual pattern.
A student could use basic geometry and maps to assess the scale (one million km sides) against known spacecraft separations and conclude whether Voyagerâ2 could plausibly be part of such a formation.
This statement analysis shows book citations, web sources and indirect clues. The first statement (S1) is open for preview.
Login with Google to unlock all statements.
This statement analysis shows book citations, web sources and indirect clues. The first statement (S1) is open for preview.
Login with Google to unlock all statements.
This statement analysis shows book citations, web sources and indirect clues. The first statement (S1) is open for preview.
Login with Google to unlock all statements.
This tab shows concrete study steps: what to underline in books, how to map current affairs, and how to prepare for similar questions.
Login with Google to unlock study guidance.
Discover the small, exam-centric ideas hidden in this question and where they appear in your books and notes.
Login with Google to unlock micro-concepts.
Access hidden traps, elimination shortcuts, and Mains connections that give you an edge on every question.
Login with Google to unlock The Vault.