Space Missions
Short Questions
1. What is an artificial satellite?
Answer : An artificial satellite is a man-made object that revolves around the Earth or another planet in a fixed orbit.
2. Who was the first person to orbit the Earth?
Answer : Yuri Gagarin of the USSR orbited the Earth in 1961.
3. What was the first artificial satellite launched into space?
Answer : Sputnik was the first artificial satellite, launched by the Soviet Union in 1957.
4. What powers most artificial satellites?
Answer : Most artificial satellites are powered by solar energy using photovoltaic panels.
5. What is the purpose of geosynchronous satellites?
Answer : Geosynchronous satellites are used for communication, meteorology, and broadcasting as they appear stationary relative to Earth.
6. What is the escape velocity of Earth?
Answer : The escape velocity of Earth is 11.2 km/s.
7. What is a polar orbit?
Answer : A polar orbit is an elliptical medium Earth orbit passing over the polar regions, used for studying these areas.
8. What is the function of the INSAT satellite series?
Answer : INSAT satellites support telecommunication, television broadcasting, and meteorological services in India.
9. What is the critical velocity of a satellite?
Answer : Critical velocity is the tangential velocity required for a satellite to maintain a stable orbit around Earth.
10. What is the primary fuel source for satellite launch vehicles?
Answer : Satellite launch vehicles use specific fuels that combust to produce thrust, propelling the vehicle into space.
11. What is the role of ISRO in India’s space program?
Answer : ISRO develops and launches satellites and launch vehicles, contributing to India’s space research and applications.
12. What was the significant discovery of Chandrayaan-1?
Answer : Chandrayaan-1 discovered the presence of water on the Moon’s surface.
13. What is space debris?
Answer : Space debris includes non-functional satellites, launcher parts, and collision fragments orbiting Earth.
14. What is the purpose of the IRNSS satellite series?
Answer : IRNSS provides precise location data for navigation, determining latitude and longitude across India.
15. Why are multi-stage launch vehicles used?
Answer : Multi-stage launch vehicles reduce weight during flight by detaching empty fuel tanks, increasing efficiency.
Long Questions
1. Explain the importance of space missions in modern society.
Answer : Space missions enable global communication, internet access, and real-time weather forecasting, connecting the world. They provide critical data for disaster management, resource exploration, and national security through surveillance. Satellites facilitate education, navigation, and scientific research, driving national development.
2. Describe the classification of artificial satellites based on their functions.
Answer : Artificial satellites are classified into communication (e.g., INSAT), navigation (e.g., IRNSS), remote sensing (e.g., IRS), and weather satellites. Communication satellites handle telecom and broadcasting, while navigation satellites provide location services. Remote sensing and weather satellites monitor Earth’s resources, climate, and natural phenomena.
3. How are the orbits of artificial satellites classified based on height?
Answer : Satellite orbits are classified as Low Earth Orbits (180-2000 km), Medium Earth Orbits (2000-35780 km), and High Earth Orbits (>35780 km). Low Earth Orbits host scientific satellites, Medium Earth Orbits include polar and navigation satellites, and High Earth Orbits house geosynchronous satellites. The orbit height determines the satellite’s function and revolution time.
4. Why are geosynchronous satellites significant, and what are their limitations?
Answer : Geosynchronous satellites, at 35780 km, appear stationary, enabling continuous monitoring for communication and meteorology. They are ideal for equatorial regions but cannot effectively observe polar regions due to their fixed position over the equator. Polar orbits are used instead for polar studies.
5. Explain the working principle of satellite launch vehicles.
Answer : Satellite launch vehicles operate on Newton’s third law, where combustion gases are expelled to generate thrust. Multi-stage vehicles discard empty fuel tanks to reduce weight, improving efficiency. Fuels and engines are tailored to the satellite’s weight and target orbit.
6. Describe the structure and advantages of a multi-stage launch vehicle like PSLV.
Answer : PSLV has multiple stages, each with solid or liquid fuel, e.g., solid fuel in the first stage and liquid in the second. After each stage’s fuel is exhausted, it detaches, reducing the vehicle’s weight for higher speed. This design allows heavier satellites to reach precise orbits economically.
7. What are the challenges posed by space debris, and why is its management crucial?
Answer : Space debris, including defunct satellites and collision fragments, can damage operational satellites and spacecraft. With over 2 crore pieces larger than 1 cm, it threatens future missions. Effective management is essential to ensure safe satellite launches and space exploration.
8. Discuss the significance of India’s Chandrayaan-1 and Mangalyaan missions.
Answer : Chandrayaan-1, launched in 2008, confirmed water on the Moon, a global first, enhancing lunar research. Mangalyaan, orbiting Mars since 2014, provided valuable data on Mars’ surface and atmosphere. Both missions highlight ISRO’s cost-effective innovation in space exploration.
9. How does the critical velocity of a satellite depend on its orbital height?
Answer : Critical velocity (v_c = √(GM/(R+h))) decreases as the orbital height (h) increases, as per the formula. At higher altitudes, the gravitational pull weakens, requiring less speed to maintain orbit. This velocity ensures the satellite balances centripetal and gravitational forces.
10. Explain the contributions of Vikram Sarabhai to India’s space program.
Answer : Vikram Sarabhai founded the Physical Research Laboratory and led the establishment of ISRO. He initiated India’s first satellite, Aryabhatta, and set up the Thumba launch center. His vision drove India’s advancements in satellite technology and space research.
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