What is true of the GSLV-F15 mission by ISRO?

Question

UnlockIAS · Accepted Answer

Correct — D, More than one of the above. GSLV-F15 lifted off from the Second Launch Pad of the Satish Dhawan Space Centre SHAR, Sriharikota, at 06:23 IST on 29 January 2025, and two of the three statements offered are true of that flight. Statement (a) is true: the payload was NVS-02, the second satellite of the second-generation NavIC series — a 2,250 kg spacecraft on the I-2K bus with about 3 kW of power, carrying navigation payloads in the L1, L5 and S bands plus a ranging payload in C band, and intended to replace IRNSS-1E in the inclined geosynchronous slot that crosses the equator at 111.75° E. Statement (c) is also true: ISRO marked the flight as the 100th launch from Sriharikota, the hundredth launch-vehicle mission flown from the spaceport since the first experimental SLV-3 flight of 10 August 1979, and the centenary was the headline the agency itself led with. That leaves (b) as the single false claim in the set — 101st is one out, and it is planted to punish a candidate who remembers 'century at Sriharikota' as a slogan rather than as a number. Two of three statements standing means no single lettered statement can be the answer, and only (d) accommodates both. Note carefully what the question does not ask, because this is where well-prepared candidates over-think it: it asks what is true of the mission, not whether the mission succeeded. It did not. GSLV-F15 performed, injecting NVS-02 into a geostationary transfer orbit of roughly 165 km by 36,577 km about nineteen minutes after lift-off, but the satellite's own orbit-raising burns were never carried out, because the valves admitting oxidiser to its main engine did not open, and it never reached its operational slot. That failure is a fact about the spacecraft's fate, not about what the rocket carried or which number the launch was, so it falsifies neither (a) nor (c).

Why the other options are wrong — (a) True as a statement, wrong as an answer — and that distinction is the whole question. GSLV-F15 did carry NVS-02, the 2,250 kg second-generation NavIC satellite meant to replace IRNSS-1E. But in a 'more than one of the above' item a true statement does not automatically become the key. Statement (c) is equally true, so marking (a) alone reports half the fact set and forfeits the mark.  (b) The only genuinely false statement in the set, and the planted one. GSLV-F15 was Sriharikota's 100th launch, not its 101st — the count runs over launch-vehicle missions flown from SDSC-SHAR since the maiden SLV-3 flight of 10 August 1979, and ISRO publicised the round hundred. '101' is what a candidate writes who recalls that a milestone was crossed but not which milestone, and it sits directly above the right number so a fast scan can catch it.  (c) The mirror image of (a): true, but not the whole truth. This was indeed the 100th launch from Sriharikota, and also ISRO's first flight of 2025, the 17th GSLV mission overall and the 11th of the Mk II variant. Because statement (a) is true as well, ticking (c) alone is the same half-answer, and the paper's own fourth option exists precisely to absorb both.

Concept: NavIC — Navigation with Indian Constellation, formerly IRNSS — is India's own regional satellite-navigation system, built so that positioning over Indian territory does not depend on a foreign constellation that a foreign government can degrade. Its architecture is deliberately regional rather than global: seven satellites, three of them geostationary at 32.5° E, 83° E and 131.5° E, and four in inclined geosynchronous orbits crossing the equator at 55° E and 111.75° E. Because India lies in low latitudes, that geometry buys continuous visibility over the subcontinent with a fraction of the spacecraft a worldwide system needs — GPS runs roughly 24 to 31. The declared service volume is India plus about 1,500 km around it, with a stated position accuracy of about 5–10 m over the Indian landmass and about 20 m over the surrounding ocean, delivered at two levels: an open Standard Positioning Service, and an encrypted Restricted Service for authorised users, largely military. The second-generation NVS series — NVS-01 on GSLV-F12 (29 May 2023) and NVS-02 on GSLV-F15 (29 January 2025) — exists because the rubidium atomic clocks aboard the first-generation IRNSS satellites failed repeatedly, crippling the constellation's ability to compute position. The NVS spacecraft carry indigenous atomic clocks developed by the Space Applications Centre, Ahmedabad, lift design life from 10 to 12 years, and add the L1 band at 1575.42 MHz — the frequency civilian GPS already uses — so that ordinary phone and IoT chipsets can receive NavIC without new hardware.

State PCS 2025 Q21 — Science & Technology PYQ with Answer

State PCS 2025 Q21 — Science & Technology PYQ with Answer