Space Missions and Satellites Overview

Space Missions

• Space missions are categorized into two types: placing artificial satellites in orbit and sending spacecraft to other parts of the solar system, or beyond.
• Artificial satellites are man-made objects that orbit the Earth or other planets.
• Natural satellites are astronomical objects that orbit a planet.
• The Moon is the Earth's only natural satellite.
• Sputnik was the first artificial satellite.

Classification of Artificial Satellites

• Satellites are categorized by function, such as weather, communication, navigation, military and earth observation.
• Satellites like INSAT, GSAT, IRNSS, IRS, GSLV, and PSLV are examples of Indian satellite series and launch vehicles, showing India's involvement in space research.

Orbits of Artificial Satellites

• Artificial satellites do not have uniform orbits, the height and path vary.
• Factors determining satellite orbit: function, surface height, equatorial alignment.
• The exact velocity for placing a satellite in a specific orbit is called critical velocity. This velocity depends on the height above Earth's surface.
• Different orbital heights result in different classifications of orbits.

High Earth Orbits

• Satellites in GEO (geostationary orbits) are stationary relative to Earth to cover a fixed area, such as monitoring specific geographic locations.
• GEO orbits are at a high altitude, around 35,780 km.

Medium Earth Orbits (MEO).

• Satellites in MEO orbits orbit Earth at altitudes between 2,000 km and 35,780 km.
• They are used for communication, navigation, and surveying.

Low Earth Orbits (LEO)

• Satellites in LEO orbits are lower altitude, between 180 km and 2,000 km.
• Useful for scientific experiments and atmospheric studies, like the International Space Station and Hubble telescope.

Satellite Launch Vehicles

• Launch vehicles place satellites into their assigned orbits, following Newton's third law.
• Launch vehicles often have multiple stages, using different types of fuels. This reduces overall weight by detaching empty fuel tanks during ascent, improving fuel efficiency and enabling higher velocities.
• Some vehicles like the space shuttle are reusable.

Examples

• Example calculations determine tangential velocity and revolution time for satellites in specific orbits.
• Calculations use gravitational constant, Earth's mass and radius, orbital height and orbital radius to solve these examples.