Concepts to remember on Natural And Artificial Satellites

1. Types of Celestial bodies

   • Planets: Spherical objects that revolve around the sun in fixed elliptical paths.
   • Stars: Large, luminous balls of hot gas that produce their own light and heat.
   • Moons: Natural objects that orbit planets.
   • Asteroids: Small, rocky objects that orbit the sun, mostly found in the asteroid belt between Mars and Jupiter.
   • Comets: Small bodies made of ice and dust that have an eccentric orbit around the sun and a long, glowing tail.

2. Kepler’s laws of planetary motion Kepler’s Three Laws, proposed by Johannes Kepler, describe the motion of planets around the Sun.

   • First law: The orbit of each planet is an ellipse with the Sun at one of the two foci.
   • Second law: A line connecting a planet to the Sun sweeps out equal areas during equal intervals of time.
   • Third law: The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.

3. Laws of Gravitation

   • Newton’s law of universal gravitation states that every particle of matter in the universe attracts every other particle with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.
   • The force of gravity is what keeps the planets orbiting the sun and the moon orbiting Earth.

4. Components of our solar system

   • The sun, eight planets, dwarf planets (objects smaller than planets but larger than asteroids), asteroids, comets, meteoroids, and interplanetary dust.

5. Definition of a satellite

   • A satellite is a celestial body that orbits a planet or another celestial body.

6. Distinction between natural and artificial satellites

   • Natural satellites: Satellites that occur naturally in the universe, such as the moon orbiting Earth or Jupiter’s moons.
   • Artificial satellites: Satellites created and launched by humans for various purposes.

7. Origin and revolution of the moon around the Earth

   • The moon is believed to have formed about 4.5 billion years ago from a giant impact between Earth and a Mars-sized body called Theia.
   • The moon revolves around Earth in a nearly circular orbit taking 27.3 days to make one complete revolution.

8. Characteristics of the moon (e.g., synchronous rotation)

   • Synchronous rotation: The moon’s rotation period is the same as its orbital period, which means the same side of the moon always faces Earth.
   • Phases: The appearance of the moon changes throughout its orbit due to varying amounts of sunlight reflected on different parts of the moon facing Earth.
   • Craters: The moon’s surface is covered in craters formed by impacts from meteoroids, comets, and asteroids over billions of years.

9. Differences in appearance of the moon during various phases

   • New moon: The moon is between the Earth and the Sun, and its dark side faces Earth.
   • Waxing crescent: The lit portion of the moon increases as the moon moves in its orbit.
   • First quarter (waxing gibbous): Half of the moon is illuminated facing Earth.
   • Full moon: The entire face of the moon is lit by sunlight as seen from Earth.
   • Waning gibbous: The illuminated portion of the moon decreases as it continues its orbit.
   • Third quarter (waning crescent): Half of the moon is illuminated facing Earth.

10. Eclipses (lunar and solar) and their causes

• Lunar eclipse: Occurs when the moon passes through the shadow cast by Earth. It can occur only during the full moon.
• Solar eclipse: Occurs when the moon passes between the Earth and the sun, obscuring the Sun from view. It can only happen during the new moon.

11. Tides and their relation to the position of the moon

• Tides are the rise and fall of sea levels caused by the gravitational pull of the sun and the moon.
• High tides occur when sea levels rise due to alignment with the gravitational forces, while low tides occur when sea levels recede.

12. Orbits of planets, asteroids, and comets around the sun

• Planets orbit the sun in nearly circular orbits within a relatively flat plane called the ecliptic.
• Asteroids primarily orbit the sun in a belt between Mars and Jupiter, in an area known as the asteroid belt.
• Comets have highly eccentric orbits that bring them close to the sun and then far beyond the outer planets over long periods.

13. Artificial Satellites

• Artificial satellites are human-made objects placed into orbit around Earth or other celestial bodies.

14. Purposes and types of artificial satellites

• Communication: Relaying signals for television, radio, telephone, and internet.
• Weather forecasting: Collecting data on atmospheric conditions for weather forecasting and climate studies.
• Remote sensing: Capturing images and data of Earth’s surface for mapping, agriculture, and natural resource management.
• Navigation: Providing location information for GPS and other navigation systems.
• Scientific research: Conducting experiments in space, studying celestial bodies, and monitoring Earth’s environment.

15. Applications of artificial satellites in communication, weather forecasting, remote sensing, etc.

• Satellites enable global communication, allowing for real-time transmission of voice, data, and video signals.
• Satellite data helps meteorologists predict weather patterns, monitor climate change, and track natural disasters.
• Remote sensing satellites provide valuable information for land use planning, urban development, and environmental conservation.

16. Indian Space Research Organisation (ISRO) and its achievements

• ISRO is India’s national space agency responsible for research, development, and space exploration.
• Some of ISRO’s achievements include:
  • Developing and launching various communication satellites (INSAT series, GSAT series)
  • Launching lunar missions like Chandrayaan-1 and Chandrayaan-2
  • Mars Orbiter Mission (MOM), India’s first mission to Mars
  • Reusable launch vehicles like the Reusable Launch Vehicle (RLV)
  • Developing the Indian Regional Navigation Satellite System (IRNSS) for navigation and positioning.

17. Future of satellite technology

• Advancements in satellite technology are expected in areas such as:
  • Improved satellite communication systems for enhanced global connectivity.
  • Satellite constellations for providing high-resolution Earth observation data.
  • Development of new propulsion systems for more efficient and sustainable space travel.
  • In-orbit servicing and maintenance to extend the lifespan of satellites.
  • Exploration and utilization of space resources.