Satellites — Set 1

Correct Answer: A. Providing telecommunication services

• **Geostationary satellites** = remain fixed above one point for continuous coverage. • **35,786 km altitude** — allows orbital period to match Earth's rotation (24 hours). • 💡 Wrong-option analysis: B (mapping deep sea): remote sensing uses LEO/polar orbits, not GEO; C (weather only): GEO handles both comms and weather; D (galaxies): would need space telescope, not telecom orbit.

Correct Answer: D. Soviet Union

• **Sputnik 1** = first artificial satellite, launched by Soviet Union on 4 October 1957. • **Space Age milestone** — triggered Cold War space race; small metal sphere with 4 radio antennas. • 💡 Wrong-option analysis: A (USA): first successful satellite was Soviet; B (Germany): Germany didn't have launch capability; C (China): first launched in 1970, much later.

Correct Answer: A. 24 hours

• **GEO orbital period** = approximately 24 hours (Earth's rotation). • **Synchronized speed** — satellite appears fixed above one point from ground. • 💡 Wrong-option analysis: B (12 hours): would complete 2 orbits per day; C (90 minutes): LEO period, not GEO; D (365 days): one year—wouldn't stay synchronized.

Correct Answer: D. Sun-Synchronous Orbit

• **Sun-synchronous orbit** = passes over same location at same local solar time daily. • **Consistent lighting** — enables high-quality imagery for environmental monitoring and mapping. • 💡 Wrong-option analysis: A (Geostationary): fixed point, not sun-aligned; B (Elliptical): high eccentricity, not sun-synchronous; C (Transfer): temporary orbit, not operational.

Correct Answer: A. 160 to 2,000 km

• **LEO altitude range** = 160 to 2,000 km above Earth's surface. • **High orbital speed** — satellites move fast to balance atmospheric drag and maintain orbit. • 💡 Wrong-option analysis: B (35,000–40,000 km): GEO altitude, not LEO; C (10,000–12,000 km): beyond LEO range; D (500–1,000 m): far too low.

Correct Answer: A. Moon

• **Passive satellite** = reflects energy from other sources, generates no signal. • **Moon example** — natural passive satellite; early Echo 1 metalized balloons were artificial passive satellites. • 💡 Wrong-option analysis: B (GPS): active satellite with transmitters; C (INSAT-3D): active weather satellite; D (Hubble): active space telescope.

Correct Answer: C. Aryabhata

• **Aryabhata** = India's first satellite (1975), named after 5th-century astronomer. • **Soviet launch** — Kosmos-3M rocket; established foundation for ISRO's space program. • 💡 Wrong-option analysis: A (Rohini): second Indian satellite; B (Bhaskara): launched after Aryabhata; D (Apple): not India's, technical name GSAT-1.

Correct Answer: C. Solar panels

• **Solar panels** = convert sunlight into electricity for satellite instruments. • **Battery backup** — rechargeable batteries sustain power during Earth's shadow periods. • 💡 Wrong-option analysis: A (Transponder): processes signals, doesn't generate power; B (Propulsion): uses fuel, not solar; D (Antenna): receives/transmits, no power generation.

Correct Answer: D. The highest point in orbit

• **Apogee** = farthest point in elliptical orbit from Earth's center. • **Perigee opposite** — closest point where satellite reaches maximum speed. • 💡 Wrong-option analysis: A (lowest point): that's perigee, not apogee; B (launch window): not orbital; C (speed): apogee is where satellite moves slowest.

Correct Answer: A. GPS

• **GPS constellation** = 24+ satellites providing global positioning signals. • **Civilian navigation** — originally US Defense; now worldwide use in phones, vehicles, aircraft. • 💡 Wrong-option analysis: B (IRS): Indian remote sensing for imaging; C (METSAT): meteorological satellite; D (EDUSAT): educational satellite.