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Summary

Science and Technology Class 04

## Brief Discussion on the Last Class (5:07 PM)

## Clarification for Last Class (5:22 PM)

- The payload capacity of GSLV Mk II is 6000 kg( For Low earth orbit)

## Space Missions of ISRO (5:14 PM)

- ==Past Missions==: Chandrayaan 1, Astrosat, Mars Orbital Mission, Chandrayaan 2
- ==Near Future Mission==: Aditya L1, Gaganyaan, Chandrayaan 3
- ==Mission by End of Decade==: Mars Orbital Mission 2, Shukrayaan, Xposat, Space Station

## Aditya L1 Mission

## (5:46 PM)

- Aditya refers to the fact that it is a solar mission. L1 refers to lagrangian point 1.
- It is ISRO's first dedicated solar observatory which will study the outermost layers of the sun, i.e. Photosphere, Chromosphere, and corona.
- These layers will be studied in multiple wavelengths like visible light, ultraviolet light, infrared light, and X-rays.
- ==It will carry seven payloads with the following objectives:==
- (a) To study solar Corona and the mechanism of coronal mass ejection.
- (b) To study the variation of solar wind properties.
- (c) To understand the heating mechanism of the solar corona.
- (d) To measure the strength of solar particles as they travel through the interplanetary region.
- (e) Aditya Mission is going to be kept at Lagrange point 1, about 1.5 million km away from earth, towards the sun.
- ![](http://www.nasa.gov/sites/default/files/images/462977main_sun_layers_full.jpg)
- A very powerful solar flare can be a cause of concern because it can lead to power outages, can destroy satellites functioning and we can witness auroras not just on poles, but at other latitudes as well.
- Solar Corona is the aura of plasma that extends millions of km into the sky.
- Plasma is the fourth state of matter, which exists at very high temperatures. At such high temperatures, electrons come out of the atom and coexist together with positive ions.

## Lagrangian Points and Halo Orbits

## (7:09 PM)

- ![](https://solarsystem.nasa.gov/internal_resources/3323)
- Three body problems i.e. three objects of comparable mass, and their movement only because of gravitational attraction are very complex to analyze.
- Lagrange found an exception, if the third object is very small, compared to the other two massive objects, then we can find five special points in space.
- At these five points, the third smaller object can maintain a stable orbit.
- However, the required centripetal force will come from, the combined gravitational effect of two heavier objects.
- For any two gravitationally bound systems, we can get five Lagrange points.
- For example, Sun-earth, Earth-Moon, Sun-Jupiter, etc.
- The unique characteristic of Lagrange point is that they can be orbited around.
- Thus Aditya's mission will orbit around L1, which is approximately 1.5 million km away from the earth towards the sun. This orbit is called the Halo orbit.
- The actual orbit around the sun will be a complicated three-dimensional orbit.
- This is because, the L1 point itself is revolving around the sun, along with Earth's revolution.
- The benefit of the L1 point is, that we can continuously monitor the sun without any eclipse and at the same time, can maintain the communication channel with earth.
- NASA has a famous mission called SOHO around L1.
- L2 point is suitable for astronomy. It is also 1.5 million km from earth, however, opposite to the sun earth direction.
- A telescope can observe deep space without coming into the shadow of the earth or the moon.
- Here, the James Webb space telescope has been placed. It is a collaboration between, NASA, the European space agency, and the Canadian space agency.
- L3 is not very useful, because it always remains behind the sun.
- While L1, L2, and L3 are semi-stable, L4 and L5 are examples of stable equilibrium. In the future, they will also be useful.

## Gaganyaan Mission (7:53 PM)

- ISRO is planning for a manned space mission for the first time.
- A group of three astronauts will spend 5-7 days, in low earth orbit
- before the manned mission, two missions will be launched to check the feasibility of the manned mission.
- ==Challenges to Gaganyaan Mission==
- (a) When all stages of the rocket, separate properly and the orbital module carrying astronauts will be safely ejected into orbit, one part of the mission will become successful.
- (b) Spending time in space in microgravity conditions, with no safety from cosmic radiation, and a limited supply of food, water, and oxygen will be very challenging.
- (c) reentry into the atmosphere will generate a lot of heat and will require precision.
- A small error can end in a disaster.
- (d) There is always a debate about such costly missions vs, the social sector expenditure.
- ==Benefits of the Gaganyaan Mission==
- There are both tangible and non-tangible benefits
- (a) Research and development into space lead to many spin-off technologies.
- For example, Remote surgery, laser surgery, to enhance the shelf life of food (for astronauts), use of thermal-resistant materials, and some sewage treatment plans, among many others, have various applications on earth, developed because of space research.
- (b) ISRO can become a key player in space tourism, which is an emerging economic sector.
- (c) ISRO aims to build a space station. A successful manned mission will be the first step in this direction.
- (d) India projects its space capabilities as soft power. A successful manned mission will further enhance this capability.
- (e) It will inspire the younger generation to pursue science and technology.

## The topics for the next class: Space Debris, Nuclear technology