GS Paper III — Q15
Launched on 25th December, 2021, James Webb Space Telescope has been much in the news since then. What are its unique features…
Launched on 25th December, 2021, James Webb Space Telescope has been much in the news since then. What are its unique features which make it superior to its predecessor Space Telescopes? What are the key goals of this mission? What potential benefits does it hold for the human race? (Answer in 250 words) 15 marks
हिंदी में प्रश्न पढ़ें
25 दिसंबर, 2021 को छोड़ा गया जेम्स वेब अंतरिक्ष टेलीस्कोप तभी से समाचारों में बना हुआ है। उसमें ऐसी कौन-कौन सी अनन्य विशेषताएं हैं जो उसे इससे पहले के अंतरिक्ष टेलीस्कोपों से श्रेष्ठ बनाती हैं? इस मिशन के मुख्य ध्येय क्या हैं? मानव जाति के लिए इसके क्या संभावित लाभ हो सकते हैं? (250 शब्दों में उत्तर दीजिए)
Model answer
Drafted with AI by UPSC Answer Check against this question's marking rubric, to the 250-word length. UPSC does not publish answers for Mains — this is one way to score well, not an official key. How we build rubrics and answers.
The James Webb Space Telescope (JWST), operating at the Sun-Earth Lagrange Point 2 (L2), represents a generational leap in observational astronomy, overcoming the optical and thermal constraints of predecessors like Hubble and Spitzer.
Unique Features and Superiority JWST features a 6.5-metre primary mirror composed of 18 hexagonal beryllium segments coated with gold, offering over six times the light-collecting area of Hubble’s 2.4-metre mirror. Situated in a halo orbit at L2 (1.5 million km from Earth) rather than Low Earth Orbit, it avoids Earth's thermal interference. A five-layer tennis-court-sized sunshield ensures passive cryogenic cooling below -233°C. This allows instruments like the Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI) to operate across 0.6 to 28 microns. This infrared sensitivity penetrates dense cosmic dust and detects ancient, redshifted light invisible to optical telescopes.
Key Mission Goals JWST is structured around four primary objectives: First Light and Reionization: Capturing the earliest stars and galaxies formed after the Big Bang, as validated by the JADES survey. Assembly of Galaxies: Tracing structural evolution over cosmic time. Birth of Stars and Protoplanetary Systems: Peering through stellar nurseries to understand planetary formation. Exoplanetary Atmospheres: Analyzing chemical compositions and biosignatures, demonstrated by detecting carbon dioxide on WASP-39b.
Benefits to Humanity and Relevance for India JWST expands fundamental knowledge of cosmic origins and planetary habitability. The mission drives tangible technological spin-offs in wavefront sensing, laser interferometry, and medical ophthalmology, while inspiring global STEM education. For India, JWST’s deep-space engineering provides operational lessons for ISRO’s Aditya-L1 and future AstroSat-2 missions, bolstering collaborative avenues under frameworks like NASA-ISRO (NISAR).
How this answer will be evaluated
Framework: Technology: why it matters, use, benefit, risk, policy
What earns full marks: Detailed technical features, clear goals, and specific benefits with comparison to Hubble.
Evaluation rubric
Each sub-part is marked on its own, against the marks and word limit printed on the paper.
- The answer Explain unique features, key goals, and potential benefits of JWST. 15 marks · 250 words
explain— definition/context → points in order → small example → short close
Must cover
- Identify unique features (e.g., 6.5m mirror, infrared capability, L2 orbit).
- State key goals (e.g., first galaxies, exoplanet atmospheres, star formation).
- List potential benefits for humanity (e.g., understanding universe origins, habitability).
- Compare with predecessor (Hubble) to show superiority.
Loses marks
- Vague generalities without specific technical details.
- Confusing JWST with Hubble or other telescopes.
- Ignoring the 'superiority' aspect of the question.
Earns more
- Mention specific technical specs (e.g., gold-coated beryllium segments).
- Reference specific scientific targets (e.g., TRAPPIST-1, exoplanet biosignatures).
- Discuss the role of the sunshield.
Extra mark
- Mention specific mission partners (NASA, ESA, CSA).
What "Explain" is asking you to do
Make the working of something clear — what sets it off, what follows from what, and what it produces. Explain is the Commission's mechanism word: it dominates the technical papers and the “explain why” stems, where the marks sit in the causal chain and not in the label.
Structure that answers it
State what it is → the initiating condition → the chain of cause, step by step → an instance where it plays out → what the chain produces
Where marks are lost
Describing what something looks like instead of why it works that way. Naming the stages without linking them reads as description too.
Practice this exact question
Write your answer and it is marked point by point against the model answer above — what you covered, what you missed, what you got wrong.
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