Page 1 of 145 SCIENCE AND TECHNOLOGY Page 2 of 145 CHAPTER 1: SCIENCE AND TECHNOLOGY- DEVELOPMENTS AND THEIR APPLICATIONS AND EFFECTS IN EVERYDAY LIFE 1. SPACE SCIENCE Orbit: It refers to the fixed trajectory in which a celestial body e.g. planet Earth (or even a satellite) revolves around the larger body e.g. the Sun, with which it is bound by gravitational force. General Classification of Satellites Polar Orbiters Geostationary orbiters Satellites launched in space around the Earth are generally placed in either of the the following orbits depending on their purpose; a. Geosynchronous Orbit b. Geostationary Orbit c. Geosynchronous Transfer Orbit d. Polar Orbit e. Sun Synchronous Polar Orbit The first two are defined on the basis of following conditions: ● Condition 1: If the satellite is placed at an altitude of 35786 km above the Earth, where its velocity is such that it takes exactly 23 hrs 56 minutes 4 sec to revolve around the Earth. ● Condition 2: If the Orbital plane and the Equatorial plane lies in the same plane throughout. If both the above conditions are satisfied, the satellite is said to be placed in Geostationary orbit. If only condition 1 is satisfied, the orbit is called as Geosynchronous orbit. Thus all Geostationary orbits are Geosynchronous as well, while the vice versa is not true. The Geostationary satellites remain permanently fixed with respect to a point on earth while the Geosynchronous satellites have a varying position with respect to a point on earth and wider coverage. ForumIAS Guidance Center 2nd Floor, IAPL House, 19, Pusa Road, Karol Bagh, New Delhi – 110005 | [email protected]|982171160 Page 3 of 145 Geosynchronous Transfer Orbit refers to an elliptical Geosynchronous orbit from where the satellite is transferred to a higher orbit or to Geostationary orbit through orbit maneuvering. The Sun Synchronous Polar Orbit or the Polar orbit refers to a Low Earth Orbit in the polar plane. From this orbit, when the satellite observes a given ground location, the sun is always at the same location in the sky. When a satellite has a sun-synchronous polar orbit, it means that it 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. Launching of Satellite into Orbit: The satellites are launched vertically, so that it crosses the thickest portion of the atmosphere as quickly as possible. However, once it reaches a desired, predetermined altitude, most of the rockets’ propelling power is then used to accelerate it horizontally so that it enters a stable orbit around the planet. Since the gravitational pull of Earth is highest in the LEO, satellites in the LEO are more strongly pulled by the planet than those in the MEO or geostationary orbit. Because of this, the satellites in the LEO travel much faster (i.e., they have a high orbital velocity) than the ones in higher orbits. And whereas if it orbits at high Velocity at higher altitudes, Centrifugal force may be observed and will lose its orbit. The rocket has to get into various orbits of smaller radius before reaching the orbit of required radius. The four orbit stages involved in the satellite launch procedure are as follows: 1. Circular low earth orbit 2. Hohmann elliptical transfer orbit 3. Intermediate drift orbit 4. Circular Geostationary orbit 1.1 ISRO’s GSLV Mk III News: ISRO successfully launched GSAT 29 in 2018 which is a communication satellites placed in Geostationary orbit. (The mechanism and structure of GSLV and PSLV have covered extensively under Chapter 2). ForumIAS Guidance Center 2nd Floor, IAPL House, 19, Pusa Road, Karol Bagh, New Delhi – 110005 | [email protected]|982171160 Page 4 of 145 1.1.1 Geostationary Satellite Launch Vehicle (GSLV) Mk III It is a three-stage heavy lift launch vehicle developed by ISRO to carry upto 4 ton weight satellites into GTO or about 10 tons to Low Earth Orbit (LEO). Stage 1: Two S200 solid rocket boosters to provide the huge amount of thrust required for lift off. Stage 2: Core Stage : L110 Liquid Stage Stage 3: Cryogenic Upper Stage : C25 1.1.2 Significance of GSLV Mk III ● It has made India capable of launching four-tonne satellites into geostationary orbit, relieving it from depending on foreign players to launch its heavy satellites and hence saving forex. ● It also brings India into the multibillion-dollar global commercial satellite launch market, where it can now compete with its cheaper and reliable launch capacity. ● The heavy launcher has the potential also to be used in a Indian human space programme, hence Gaganyaan mission will be launched aboard this launcher. ● It will serve as prequel for developing even heavier capacity launch vehicles in the future. ● It will give boost to R&D in space science in the country apart from reducing cost of heavy satellite launches. 1.2 GSAT 29 It is a communication satellite weighting 3423 kg launched and placed in Geostationary orbit aboard GSLV Mk III rocket in 2018. It was the 20th GSAT series satellite to be launched out of which 14 are operational as of now, using over 160 transponders for providing services related to telecommunications, television broadcasting, weather forecasting, disaster warning and search and rescue operations. 1.2.1 Significance ● It will provide high-speed bandwidth to Village Resource Centres (ISRO’s initiative) in rural areas. ForumIAS Guidance Center 2nd Floor, IAPL House, 19, Pusa Road, Karol Bagh, New Delhi – 110005 | [email protected]|982171160 Page 5 of 145 ● It is also an experimental satellite, with new technologies in Q (microwave) band and V band being tried for the first time. ● It will also help in providing better communication services to Jammu and Kashmir and Northeast India, under Digital India programme, by increasing the number of transponders in the Indian skies. ● It is the heaviest satellite lifted and placed in orbit by an Indian launch vehicle. 1.3 PSLV AND RECENT LAUNCHES PSLV or the Polar Satellite Launch Vehicle was developed by ISRO by 1993. These are rockets used to launch Earth Observation and mapping satellites (called Remote Sensing Satellite) into Sun- synchronous Low Earth Orbit and also to Geostationary Transfer orbit (although for lighter satellites). ● It is a four-stage rocket which uses solid and liquid fuel, having six strap-ons/boosters. It can launch upto 3800 kg payload in LEO, upto 1750 kg payload to Sun synchronous orbit and upto 1200 kg payload to Geostationary Transfer orbit. ● Out of its 46 missions, 43 have been successful which includes Chandrayaan I and Mangalyaan missions. 1.3.1 HySIS It was launched aboard PSLV-C43 in November 2018 and is placed in a sun-synchronous low earth orbit. It weighs around 380 kg. Significance: ● It is an earth observation satellite with the primary goal of studying the earth’s surface in the visible, near infrared and shortwave infrared regions of the electromagnetic spectrum. ● Most importantly, it will provide hyperspectral imaging services for various applications in agriculture, forestry and in the assessment of geography such as coastal zones and inland waterways. 1.3.2 Microsat-R It was launched by ISRO’s PSLV C-44 in January 2019. The satellite weighted 740 kg. It was the first of its kind to be fully developed by DRDO for military purposes. Also it is placed in a much lower polar orbit of 274 km above the earth surface. It is also an an imaging satellite but for military use only. In another first, PSLV-C44 reused its spent fourth stage as a platform for carrying out microgravity experiments and to put Kalamsat V2 into orbit. Kalamsat V2, a student payload, is the world’s lightest satellite weighting only 1.26 kg, to be successfully placed into the orbit. 1.4 CARTOSAT SERIES SATELLITES These are Earth Observation satellites indigenously developed and launched by ISRO. They form the most crucial part of Indian Remote Sensing Programme. ● These are used for Earth Mapping, Resource management and monitoring, urban planning etc. ● Till now, 8 Cartosat series satellites have been launched, the most recent one being Cartosat 2f, launched aboard PSLV C40 in January 2018. ● They are placed in Geocentric Sun synchronous orbit generally in a low earth orbit(LEO) of around 500 km, for better mapping. 1.4.1 Cartosat 2F 8th of the Cartosat series satellites, it was launched along with 30 co-passenger satellites by the PSLV C40. The satellite weighed 710 kg and is placed in a sun synchronous orbit. It will act as an another eye for land observation in India. ForumIAS Guidance Center 2nd Floor, IAPL House, 19, Pusa Road, Karol Bagh, New Delhi – 110005 | [email protected]|982171160 Page 6 of 145 1.5 INDIAN REGIONAL NAVIGATION SATELLITE SYSTEM (IRNSS) It is India’s own regional satellite system comprising 7 satellites to provide accurate position information service to users in India as well as the region extending up to 1500 km from its boundary, which is its primary service area. ● Three of the seven satellites are located in geostationary orbit of approximately 36,000 km above earth surface while remaining four satellites are in inclined geosynchronous orbit. 1.5.1 Significance ● IRNSS is designed to provide two types of services, namely, Standard Positioning Service (SPS) which is provided to all the users and Restricted Service (RS), which is an encrypted service provided only to the authorised users. ● The IRNSS System is expected to provide a position accuracy of 10-20 m in the primary service area and upto 0.1 m in restricted service area.