Question 80 from UPSC CSE 2018 - General science and Science & Technology

Question

With reference to India's satellite launch vehicles, consider the following statements:
1. PSLVs launch satellites useful for Earth resources monitoring, whereas GSLVs are designed mainly to launch communication satellites.
2. Satellites launched by PSLV appear to remain permanently fixed in the same position in the sky, as viewed from a particular location on Earth.
3. GSLV Mk III is a four-staged launch vehicle with the first and third stages using solid rocket motors and the second and fourth stages using liquid rocket engines.
Which of the statements given above is/are correct?

Accepted Answer

Correct Option: A. 1 only

Strategy: First, identify the core purpose of PSLV and GSLV:

*   PSLV is optimized for sun-synchronous and Earth observation satellites.
*   GSLV is built for high-mass, geostationary communication payloads.

This makes Statement 1 correct. Statement 2 is invalid because PSLV launches to polar orbits, not geostationary, meaning satellites do not remain fixed in the sky from such orbits. Statement 3 mistakenly describes GSLV Mk III as four-stage and incorrectly assigns propulsion types; knowledge of GSLV Mk III design (three-stage with solid, liquid, and cryogenic stages) reveals this is wrong. Therefore, only Statement 1 is correct.

Key Info: ## PSLV (Polar Satellite Launch Vehicle)

*   **Primary Purpose:** Designed for launching Earth observation and remote sensing satellites into Sun-synchronous Polar Orbits (SSO), typically at altitudes of 600-900 km.
*   **Stages & Propulsion:** A four-stage launch vehicle utilizing alternating solid and liquid propulsion systems.
*   **Orbital Capabilities:** While capable of placing satellites into Geosynchronous Transfer Orbit (GTO), it is not intended for high-mass geostationary communication satellites. Satellites in polar orbits traverse Earth from pole to pole and continuously change position relative to a fixed point on Earth, unlike geostationary satellites which remain fixed overhead at the equator.

## GSLV (Geosynchronous Satellite Launch Vehicle) / LVM3

*   **Primary Purpose:** Designed for heavier payloads, such as communication satellites, into GTO, a necessary intermediary orbit for achieving geostationary orbit.
*   **GSLV Mk III (now 'LVM3') Stages:** This vehicle is three-staged:
    *   **First Stage:** Features two solid strap-on motors.
    *   **Second Stage:** Consists of a liquid core stage.
    *   **Third Stage:** A cryogenic upper stage, employing advanced liquid hydrogen-oxygen technology.
*   **Correction:** It does not possess four stages or two liquid stages as sometimes erroneously suggested.

PSLV and GSLV fulfill complementary roles within ISRO's launch vehicle fleet.

Answer

Option B: 2 and 3

Answer

Option C: 1 and 2

Answer

Option D: 3 only