With reference to India’s satellite launch vehicles, consider the following statements: 1) PSLVs launch the 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-stage launch l vehicle with the first and third stages l using solid rocket motors; and the second and fourth stages using liquid rocket engines. Which of the statements given above is/are correct?

Statement 1 is correct, and that settles the answer. PSLV mainly places remote-sensing satellites such as the IRS and Cartosat series into sun-synchronous polar orbits, which suits Earth resources monitoring. GSLV is built to carry heavier satellites to geosynchronous transfer orbit, which is why it launches INSAT and GSAT communication satellites.

• Statement 2 is wrong. PSLV satellites sit in low polar orbits, roughly 500 to 900 km up, and keep moving across the sky. Only geostationary satellites, about 36,000 km above the equator, appear fixed from a given point on Earth.
• Statement 3 is wrong. GSLV Mk III has three stages, not four. The first stage uses two S200 solid boosters, the second is the liquid L110 Vikas stage, and the third is the cryogenic C25 stage. It was later renamed LVM3.

The core concept is matching orbit to mission and launcher. Orbit decides what a satellite can do, a point that recurs in Mains answers on space technology, connectivity and disaster management.

Trap: Candidates often assume statement 2 is true because PSLV is a workhorse launcher. Check the orbit before you check the launcher.