What is Space | Science & Technology for UPSC 2024 (Pre & Mains) PDF Download

 Page 1


 
Space 
What is Space? 
•
Zone that occurs about 100 km above Earth, where there is no appreciable air to breathe or to scatter 
light  
?In this area, blue gives way to black because oxygen molecules are not in enough abundance to make 
the sky blue  
•It is a vacuum, meaning that sound cannot carry because molecules are not close enough together to 
transmit sound between them 
?But it doesn’t mean that space is empty. Gas, dust and other bits of matter ?oat around “emptier” 
areas of the universe, while more crowded regions can host planets, stars and galaxies  
Why Explore Space? 
•
Urge to explore 
•Does life exist beyond earth? 
•
Raw materials : silver, platinum and other valuable substances  
•National Security 
•
More great inventions  
•
Protection from a catastrophic asteroid  
Satellites 
• Broadly classi?ed into two  
?Communication satellites 
?
Usually operates from the Geosynchronous orbit catering to requirements in communication, 
television, broadcasting, meteorology, disaster warning etc. 
?Remote Sensing Satellites 
?
It is intended for natural resource monitoring and management and operates from a Sun 
Synchronous Polar Orbit (SSPO) 
Types of Orbits 
•An orbit is a regular, repeating path that one object in space takes around another one. An object in an 
orbit is called a satellite 
•
Orbits come in different shapes. All orbits are elliptical 
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Page 2


 
Space 
What is Space? 
•
Zone that occurs about 100 km above Earth, where there is no appreciable air to breathe or to scatter 
light  
?In this area, blue gives way to black because oxygen molecules are not in enough abundance to make 
the sky blue  
•It is a vacuum, meaning that sound cannot carry because molecules are not close enough together to 
transmit sound between them 
?But it doesn’t mean that space is empty. Gas, dust and other bits of matter ?oat around “emptier” 
areas of the universe, while more crowded regions can host planets, stars and galaxies  
Why Explore Space? 
•
Urge to explore 
•Does life exist beyond earth? 
•
Raw materials : silver, platinum and other valuable substances  
•National Security 
•
More great inventions  
•
Protection from a catastrophic asteroid  
Satellites 
• Broadly classi?ed into two  
?Communication satellites 
?
Usually operates from the Geosynchronous orbit catering to requirements in communication, 
television, broadcasting, meteorology, disaster warning etc. 
?Remote Sensing Satellites 
?
It is intended for natural resource monitoring and management and operates from a Sun 
Synchronous Polar Orbit (SSPO) 
Types of Orbits 
•An orbit is a regular, repeating path that one object in space takes around another one. An object in an 
orbit is called a satellite 
•
Orbits come in different shapes. All orbits are elliptical 
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! 
?For the planets, the orbits are almost circular  
?The orbits of comets are highly eccentric or ‘squashed’?  
• Polar Orbits 
?As the name suggests, polar orbits pass over the Earth’s polar regions from north to south. The 
orbital track of the satellite does not have to cross the poles exactly for an orbit to be called polar, an 
orbit which passes within 20 to 30 degrees of the poles is still classed as a polar orbit 
?These orbits mainly take place at low altitudes of between 200 to 1000 km. Satellites in polar orbit 
look down on the Earth’s entire surface and can pass over the North and South Poles several times a 
day 
?Polar orbits are used for reconnaissance and Earth observation. If a satellite is in polar orbit at an 
altitude of 800 km, it will be travelling at a speed of approximately 7.5 km per second?  
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!
Page 3


 
Space 
What is Space? 
•
Zone that occurs about 100 km above Earth, where there is no appreciable air to breathe or to scatter 
light  
?In this area, blue gives way to black because oxygen molecules are not in enough abundance to make 
the sky blue  
•It is a vacuum, meaning that sound cannot carry because molecules are not close enough together to 
transmit sound between them 
?But it doesn’t mean that space is empty. Gas, dust and other bits of matter ?oat around “emptier” 
areas of the universe, while more crowded regions can host planets, stars and galaxies  
Why Explore Space? 
•
Urge to explore 
•Does life exist beyond earth? 
•
Raw materials : silver, platinum and other valuable substances  
•National Security 
•
More great inventions  
•
Protection from a catastrophic asteroid  
Satellites 
• Broadly classi?ed into two  
?Communication satellites 
?
Usually operates from the Geosynchronous orbit catering to requirements in communication, 
television, broadcasting, meteorology, disaster warning etc. 
?Remote Sensing Satellites 
?
It is intended for natural resource monitoring and management and operates from a Sun 
Synchronous Polar Orbit (SSPO) 
Types of Orbits 
•An orbit is a regular, repeating path that one object in space takes around another one. An object in an 
orbit is called a satellite 
•
Orbits come in different shapes. All orbits are elliptical 
www.YouTube.com/SleepyClasses 
www.SleepyClasses.com 
! 
?For the planets, the orbits are almost circular  
?The orbits of comets are highly eccentric or ‘squashed’?  
• Polar Orbits 
?As the name suggests, polar orbits pass over the Earth’s polar regions from north to south. The 
orbital track of the satellite does not have to cross the poles exactly for an orbit to be called polar, an 
orbit which passes within 20 to 30 degrees of the poles is still classed as a polar orbit 
?These orbits mainly take place at low altitudes of between 200 to 1000 km. Satellites in polar orbit 
look down on the Earth’s entire surface and can pass over the North and South Poles several times a 
day 
?Polar orbits are used for reconnaissance and Earth observation. If a satellite is in polar orbit at an 
altitude of 800 km, it will be travelling at a speed of approximately 7.5 km per second?  
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! 
  
•
Low Earth Orbit 
?Low Earth orbit is normally at an altitude of less than 1000 km and could be as low as 160 km above 
the Earth. Satellites in this circular orbit travel at a speed of around 7.8 km per second. At this speed, 
a satellite takes approximately 90 minutes to circle the Earth 
?In general, these orbits are used for remote sensing, military purposes and for human space?ight as 
they offer close proximity to the Earth’s surface for imaging and the short orbital periods allow for 
rapid revisits. The International Space Station is in low Earth orbit 
?Most of the manmade objects in space are in LEO 
?Importance 
?
It requires the lowest amount of energy for satellite placement  
? Provides high bandwidth and low communication latency 
?
Satellites and space stations in LEO are more accessible for crew and servicing 
•
Geosynchronous Transfer Orbit (GTO) 
?Elliptical Earth orbit used to transfer a spacecraft from a low altitude orbit or ?ight trajectory to 
geostationary orbit. The apogee is at 36 000 km. When a spacecraft reaches this point, its apogee 
kick motor is ?red to inject it into geostationary orbit 
•Geosynchronous Satellites (GEO) 
?Orbit around the equator roughly 36,000 km (22,369 mi) above the Earth 
?Uses 
?
Different  types of satellite orbits have different uses 
? While the synchronous orbit is best for communication satellites, Lagrangian point orbits 
help monitor the solar wind 
•
Geostationary Orbits (GSO) 
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!
Page 4


 
Space 
What is Space? 
•
Zone that occurs about 100 km above Earth, where there is no appreciable air to breathe or to scatter 
light  
?In this area, blue gives way to black because oxygen molecules are not in enough abundance to make 
the sky blue  
•It is a vacuum, meaning that sound cannot carry because molecules are not close enough together to 
transmit sound between them 
?But it doesn’t mean that space is empty. Gas, dust and other bits of matter ?oat around “emptier” 
areas of the universe, while more crowded regions can host planets, stars and galaxies  
Why Explore Space? 
•
Urge to explore 
•Does life exist beyond earth? 
•
Raw materials : silver, platinum and other valuable substances  
•National Security 
•
More great inventions  
•
Protection from a catastrophic asteroid  
Satellites 
• Broadly classi?ed into two  
?Communication satellites 
?
Usually operates from the Geosynchronous orbit catering to requirements in communication, 
television, broadcasting, meteorology, disaster warning etc. 
?Remote Sensing Satellites 
?
It is intended for natural resource monitoring and management and operates from a Sun 
Synchronous Polar Orbit (SSPO) 
Types of Orbits 
•An orbit is a regular, repeating path that one object in space takes around another one. An object in an 
orbit is called a satellite 
•
Orbits come in different shapes. All orbits are elliptical 
www.YouTube.com/SleepyClasses 
www.SleepyClasses.com 
! 
?For the planets, the orbits are almost circular  
?The orbits of comets are highly eccentric or ‘squashed’?  
• Polar Orbits 
?As the name suggests, polar orbits pass over the Earth’s polar regions from north to south. The 
orbital track of the satellite does not have to cross the poles exactly for an orbit to be called polar, an 
orbit which passes within 20 to 30 degrees of the poles is still classed as a polar orbit 
?These orbits mainly take place at low altitudes of between 200 to 1000 km. Satellites in polar orbit 
look down on the Earth’s entire surface and can pass over the North and South Poles several times a 
day 
?Polar orbits are used for reconnaissance and Earth observation. If a satellite is in polar orbit at an 
altitude of 800 km, it will be travelling at a speed of approximately 7.5 km per second?  
www.YouTube.com/SleepyClasses 
www.SleepyClasses.com 
! 
  
•
Low Earth Orbit 
?Low Earth orbit is normally at an altitude of less than 1000 km and could be as low as 160 km above 
the Earth. Satellites in this circular orbit travel at a speed of around 7.8 km per second. At this speed, 
a satellite takes approximately 90 minutes to circle the Earth 
?In general, these orbits are used for remote sensing, military purposes and for human space?ight as 
they offer close proximity to the Earth’s surface for imaging and the short orbital periods allow for 
rapid revisits. The International Space Station is in low Earth orbit 
?Most of the manmade objects in space are in LEO 
?Importance 
?
It requires the lowest amount of energy for satellite placement  
? Provides high bandwidth and low communication latency 
?
Satellites and space stations in LEO are more accessible for crew and servicing 
•
Geosynchronous Transfer Orbit (GTO) 
?Elliptical Earth orbit used to transfer a spacecraft from a low altitude orbit or ?ight trajectory to 
geostationary orbit. The apogee is at 36 000 km. When a spacecraft reaches this point, its apogee 
kick motor is ?red to inject it into geostationary orbit 
•Geosynchronous Satellites (GEO) 
?Orbit around the equator roughly 36,000 km (22,369 mi) above the Earth 
?Uses 
?
Different  types of satellite orbits have different uses 
? While the synchronous orbit is best for communication satellites, Lagrangian point orbits 
help monitor the solar wind 
•
Geostationary Orbits (GSO) 
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! 
?Orbits where satellites are synchronized with the Earth's rotation, orbiting once every 24 hours, 
and appear to observers on the ground as stationary in the sky 
?Geostationary satellites are launched into orbit in the same direction the Earth is spinning. When 
the satellite is in orbit at a speci?c altitude, it will exactly match the rotation of the Earth. This sweet 
spot is approximately 36,000 km above the Earth’s surface in high Earth orbit 
?An observer on Earth would be able to continuously “see” it because the satellite follows the Earth’s 
rotation always at the same point  
?In the case of geostationary satellites, the Earth’s force of gravity is exactly enough to provide 
acceleration required for circular motion 
?Weather, communication and global positioning satellites are often in geostationary orbit ?  
•
Sun-synchronous Orbits 
?These are polar orbits which are synchronous with the Sun. A satellite in a sun synchronous orbit 
would usually be at an altitude of between 600 to 800 km. Generally these orbits are used for Earth 
observation, solar study, weather forecasting and reconnaissance, as ground observation is 
improved if the surface is always illuminated by the Sun at the same angle when viewed from the 
satellite 
?In this orbit, the satellites has a constant sun illumination through inclination and altitude. For sun-
synchronous orbits, it passes over any given point on Earth’s surface at the same local solar time 
?Because of the consistent lighting in sun-synchronous orbits, scientists leverage this in various 
remote sensing applications 
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!
Page 5


 
Space 
What is Space? 
•
Zone that occurs about 100 km above Earth, where there is no appreciable air to breathe or to scatter 
light  
?In this area, blue gives way to black because oxygen molecules are not in enough abundance to make 
the sky blue  
•It is a vacuum, meaning that sound cannot carry because molecules are not close enough together to 
transmit sound between them 
?But it doesn’t mean that space is empty. Gas, dust and other bits of matter ?oat around “emptier” 
areas of the universe, while more crowded regions can host planets, stars and galaxies  
Why Explore Space? 
•
Urge to explore 
•Does life exist beyond earth? 
•
Raw materials : silver, platinum and other valuable substances  
•National Security 
•
More great inventions  
•
Protection from a catastrophic asteroid  
Satellites 
• Broadly classi?ed into two  
?Communication satellites 
?
Usually operates from the Geosynchronous orbit catering to requirements in communication, 
television, broadcasting, meteorology, disaster warning etc. 
?Remote Sensing Satellites 
?
It is intended for natural resource monitoring and management and operates from a Sun 
Synchronous Polar Orbit (SSPO) 
Types of Orbits 
•An orbit is a regular, repeating path that one object in space takes around another one. An object in an 
orbit is called a satellite 
•
Orbits come in different shapes. All orbits are elliptical 
www.YouTube.com/SleepyClasses 
www.SleepyClasses.com 
! 
?For the planets, the orbits are almost circular  
?The orbits of comets are highly eccentric or ‘squashed’?  
• Polar Orbits 
?As the name suggests, polar orbits pass over the Earth’s polar regions from north to south. The 
orbital track of the satellite does not have to cross the poles exactly for an orbit to be called polar, an 
orbit which passes within 20 to 30 degrees of the poles is still classed as a polar orbit 
?These orbits mainly take place at low altitudes of between 200 to 1000 km. Satellites in polar orbit 
look down on the Earth’s entire surface and can pass over the North and South Poles several times a 
day 
?Polar orbits are used for reconnaissance and Earth observation. If a satellite is in polar orbit at an 
altitude of 800 km, it will be travelling at a speed of approximately 7.5 km per second?  
www.YouTube.com/SleepyClasses 
www.SleepyClasses.com 
! 
  
•
Low Earth Orbit 
?Low Earth orbit is normally at an altitude of less than 1000 km and could be as low as 160 km above 
the Earth. Satellites in this circular orbit travel at a speed of around 7.8 km per second. At this speed, 
a satellite takes approximately 90 minutes to circle the Earth 
?In general, these orbits are used for remote sensing, military purposes and for human space?ight as 
they offer close proximity to the Earth’s surface for imaging and the short orbital periods allow for 
rapid revisits. The International Space Station is in low Earth orbit 
?Most of the manmade objects in space are in LEO 
?Importance 
?
It requires the lowest amount of energy for satellite placement  
? Provides high bandwidth and low communication latency 
?
Satellites and space stations in LEO are more accessible for crew and servicing 
•
Geosynchronous Transfer Orbit (GTO) 
?Elliptical Earth orbit used to transfer a spacecraft from a low altitude orbit or ?ight trajectory to 
geostationary orbit. The apogee is at 36 000 km. When a spacecraft reaches this point, its apogee 
kick motor is ?red to inject it into geostationary orbit 
•Geosynchronous Satellites (GEO) 
?Orbit around the equator roughly 36,000 km (22,369 mi) above the Earth 
?Uses 
?
Different  types of satellite orbits have different uses 
? While the synchronous orbit is best for communication satellites, Lagrangian point orbits 
help monitor the solar wind 
•
Geostationary Orbits (GSO) 
www.YouTube.com/SleepyClasses 
www.SleepyClasses.com 
! 
?Orbits where satellites are synchronized with the Earth's rotation, orbiting once every 24 hours, 
and appear to observers on the ground as stationary in the sky 
?Geostationary satellites are launched into orbit in the same direction the Earth is spinning. When 
the satellite is in orbit at a speci?c altitude, it will exactly match the rotation of the Earth. This sweet 
spot is approximately 36,000 km above the Earth’s surface in high Earth orbit 
?An observer on Earth would be able to continuously “see” it because the satellite follows the Earth’s 
rotation always at the same point  
?In the case of geostationary satellites, the Earth’s force of gravity is exactly enough to provide 
acceleration required for circular motion 
?Weather, communication and global positioning satellites are often in geostationary orbit ?  
•
Sun-synchronous Orbits 
?These are polar orbits which are synchronous with the Sun. A satellite in a sun synchronous orbit 
would usually be at an altitude of between 600 to 800 km. Generally these orbits are used for Earth 
observation, solar study, weather forecasting and reconnaissance, as ground observation is 
improved if the surface is always illuminated by the Sun at the same angle when viewed from the 
satellite 
?In this orbit, the satellites has a constant sun illumination through inclination and altitude. For sun-
synchronous orbits, it passes over any given point on Earth’s surface at the same local solar time 
?Because of the consistent lighting in sun-synchronous orbits, scientists leverage this in various 
remote sensing applications 
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?  
Indian Space Research Organisation 
•
The space research activities were initiated in our country during the early 1960’s, when applications 
using satellites were in experimental stages even in the United States 
•ISRO has been an active member of UNOOSA since its inception   
•
Dr. Vikram Sarabhai, the founding father of Indian space programme, quickly recognized the bene?ts of 
space technologies for India 
•
There are 6 major Centres and several other Units, Agencies, Facilities and Laboratories spread across 
the country 
•Since inception, the Indian space programme had three distinct elements such as,  
?satellites for communication and remote sensing 
?the space transportation system 
?application programmes 
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