- Space missions are of two types: launching satellites around Earth and exploring space objects beyond Earth.
- Yuri Gagarin was the first human in space (1961), and Neil Armstrong was the first on the Moon (1969).
- Indian space explorers include Rakesh Sharma, Kalpana Chawla, and Sunita Williams.
- Space technology enables fast global communication, internet access, and early warning of natural disasters.
- Satellites support defence, surveillance, weather forecasting, and the location of natural resources, making space tech vital for national development.
Definitions [2]
Define time period of a satellite.
Time taken by the satellite to complete one revolution round the Earth is called time period.
Time period, T = `"Distance covered"/"Orbital velocity"`
T = `"2πr"/"v"`
Definition: Artificial Satellite
If a manmade object revolves around the earth or any other planet in a fixed orbit it is called an artificial satellite.
Formulae [1]
Formula: Escape Velocity
vesc = \[\sqrt{\frac{2\mathrm{~GM}}{\mathrm{R}}}\]
where
- G = Gravitational constant
- M = mass of the planet
- R = Radius of the planet
Key Points
Key Points: Space Missions
Key Points: Artificial Satellites
- Natural satellites are natural (like the Moon); artificial satellites are manmade and orbit planets.
- Sputnik was the first artificial satellite, launched by the USSR in 1957.
- Satellites use solar panels for energy and send/receive signals.
- Types of satellites: weather, communication, broadcast, navigation, military, and Earth observation.
- India uses INSAT, GSAT, IRNSS, and IRS satellites, launched by GSLV and PSLV rockets.
Key Points: Orbits of Artificial Satellites
- Satellites are placed into orbit using launchers and require a specific tangential speed (the critical velocity).
- Low Earth Orbits (180–2000 km) are used for space stations and weather studies.
- Medium Earth Orbits (2000–35780 km) are used for GPS and polar satellites.
- High Earth Orbits (≥35780 km) include geostationary satellites used for TV, phone, and weather.
- The higher the orbit, the lower the speed needed; satellite speed doesn’t depend on its mass.
Key Points: Satellite Launch Vehicles
- Satellite launch vehicles work on Newton’s third law—expelling gas creates thrust to lift the rocket.
- Launch vehicles use multiple stages to reduce weight and increase speed as they rise.
- Fuel type and structure of launch vehicles depend on the satellite’s weight and target orbit.
- PSLV (by ISRO) is a multi-stage launch vehicle used to place satellites in orbit.
- Unlike rockets, reusable space shuttles (such as NASA's) can return and be reused.
Key Points: Moon Missions
- Since the Moon is the closest celestial body, it became the first target of space missions in the solar system.
- The Soviet Union’s Luna‑2 (1959) was the first spacecraft to reach the Moon; later Luna missions studied its composition, gravity, and radiation.
- Some unmanned Soviet missions successfully landed on the Moon and returned rock samples to Earth.
- The USA conducted manned Moon missions, and in 1969, Neil Armstrong became the first human to walk on the Moon.
- India’s Chandrayaan‑1 (2008) discovered the presence of water on the Moon, making India the first country to do so.
Key Points: Mars Missions
- Mars Mission (Mangalyaan) by ISRO was launched in 2013 and successfully entered Mars orbit in 2014.
- It was a low-cost mission that provided important data on Mars' surface and atmosphere.
- Rakesh Sharma was the first Indian in space (1984), and stayed 8 days under the Indo-USSR program.
- Kalpana Chawla spent 336 hours in space but died in 2003 during the Columbia shuttle disaster.
- Sunita Williams worked 29 hours outside the space station and spent 192 days in space, setting a record.
Key Points: India and Space Technology
- India developed PSLV and GSLV launchers to place satellites up to 2500 kg into all types of orbits.
- INSAT, GSAT, EDUSAT, IRS, and IRNSS satellite series serve communication, education, disaster management, and navigation.
- Satellite Launch Centres: Thumba (Thiruvananthapuram), Sriharikota, and Chandipur (Odisha).
- Space Research Centers: Vikram Sarabhai Space Center, Satish Dhawan Space Center, and Space Application Center.
- Vikram Sarabhai, the father of India’s space program, led the launch of Aryabhata and helped establish ISRO.
Important Questions [14]
- Suggest the ways to manage space debris.
- By considering first correlation complete the second correlation: Hubble telescope: 569 km high from the earth surface Revolving orbit of Hubble telescope: ______
- What is meant by space debris?
- State the importance of Space Missions.
- What is meant by an artificial satellite? How are the satellites classified based on their functions?
- The orbit of a satellite is exactly 35780 km above the earth's surface and its tangential velocity is 3.08 km/s. How much time the satellite will take to complete one revolution around the earth?
- The height of medium earth orbit above the surface of the earth is ______.
- Write the name of small satellite made by a group of students from COEP (College of Engineering, Pune) sent to the space through ISRO in 2016.
- Complete the Following table. Sr. no. Type of satellite (1) Navigational Satellite (2) Earth Observation Satellite The names of Indian satellite and launcher
- Name the first artificial satellite sent by Russia in space.
- The functioning of the satellite launch vehicle is based on ______.
- Name any one Indian satellite launch vehicle.
- What is meant by a satellite launch vehicle?
- The astronomical object closest to us is _________ in our galaxy.
