Space technology (Mains Notes)

Introduction to Space Technology

Space technology refers to the set of tools, equipment, satellites, space stations, rockets, and systems developed to explore, utilize, and observe outer space. It includes all the applications that allow humans to understand space phenomena, communicate across the globe, and monitor Earth for science and security.

Applications span communication, navigation, Earth observation, environmental monitoring, weather forecasting, defense, and scientific exploration.

Orbits and Satellite Types

Understanding space technology begins with understanding orbits, because they define how satellites operate and what missions they serve.

Terms and Concepts related to Satellite Launches and Satellite Orbits

• The terms like Kepler’s laws, geosynchronous orbit, geostationary orbit, polar orbit, PSLV, GSLV, etc. keep on appearing in the news columns whenever there is a satellite launch.
• So, I thought it is better to keep all the related concepts at one place.

Titbit: Russia’s Sputnik, the world’s first artificial satellite, was launched in 1957.

Kepler’s laws of planetary motion (applicable to satellites also)

• Kepler’s First Law: The orbit of a planet is an ellipse with the Sun at one of the two foci.
• Kepler’s Second Law: A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.
• In simple words, the speed of the planet increases as it nears the sun and decreases as it recedes from the sun.

The varying orbital speed of the earth (in the figure, the orbit of the earth is exaggerated)

• Kepler’s Third Law: The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit.

Hankwang, Wikipedia

• In simple terms,the distance of a planet from the sun determines the time it takes for that planet to revolve around the sun (farther the planet is, greater the orbital period). 

Planet	Orbital Period (T) in years	Average Distance (R) in AU	T2/R3
Mercury	0.241	0.39	0.98
Venus	.615	0.72	1.01
Earth	1.00	1.00	1.00
Mars	1.88	1.52	1.01

Perigee and Apogee

• Most satellites orbit the earth in elliptical patterns.
• When a satellite is at its farthest point from the earth, it is at the apogee of the orbit.
• When a satellite is at its closest point to the earth, it is at the perigee of the orbit.
• In accordance with Kepler’s second law, the satellites are fastest at the perigee and slowest at the apogee.

Why satellites revolve rather than staying still in space?

• There are two important forces acting on the satellite:
• the gravitational force which will pull the satellite towards earth and
• the centrifugal force (due to revolution) which counters the gravitational pull.

Source

• Revolution causes centrifugal force (the object tends to move away from the centre).
• Higher the speed of the revolving satellite (orbital velocity), higher the centrifugal force.
• Thus, by varying the speed (orbital velocity) of the satellite, we can make the satellite
• fall back to earth by decreasing the orbital velocity (centrifugal force < gravitational force)
• stay in its orbit by adjusting the speed so that the centrifugal force balances the gravitational pull (centrifugal force = gravitational force). (Lower the orbit, higher should be the orbital velocity).
• escape earth’s influence by keeping the orbital velocity above the required speed (centrifugal force > gravitational force).

Low Earth Orbit (LEO: 200-2000 km)

• International Space Station (400 km), the Hubble Space Telescope (560 km) and some observation satellites are all rotating the earth in Low Earth Orbit.
• LEO is high enough to significantly reduce the atmospheric drag yet close enough to observe the earth (remote sensing).
• In LEO, the satellite’s orbital period is much smaller than the earth’s rotational period (24 hours).
• That is, the satellites in LEO complete multiple revolutions in 24 hours (Lower the orbit, higher should be the speed).

Source

What is the speed required to keep a satellite in LEO?

• The speed is dependent on the distance from the centre of the Earth.
• At an altitude of 200 km, the required orbital velocity is a little more than 27,400 kmph.
• In the case of the space shuttle, it orbits the Earth once every 90 minutes at an altitude of 466 km.

Advantages of LEO

• Low Earth Orbit is used for things that we want to visit often, like the International Space Station, the Hubble Space Telescope and some satellites (usually spy satellites and other observation satellites).
• This is convenient for installing new instruments, experiments, and return to earth in a relatively short time.

Disadvantages of LEO

• Atmospheric drag will lead to more fuel consumption and constant speed adjustments.
• A satellite traveling in LEO do not spend very long over any one part of the Earth at a given time.
• Hence, satellites in LEO are not suitable for communication and weather observation and forecasting.

Solution

• One solution is to put a satellite in a highly elliptical orbit (eccentric orbit ― non-geosynchronous).
• The other is to place the satellite in a geosynchronous orbit.

Highly Elliptical Orbits

• Kepler’s second law: an object in orbit about Earth moves much faster when it is close to Earth than when it is farther away.
• Perigee is the closest point and apogee is the farthest.
• If the orbit is very elliptical, the satellite will spend most of its time near apogee (the furthest point in its orbit) where it moves very slowly.
• Thus, it can be above a specific location most of the time.

Disadvantages of Highly Elliptical Orbits

• In a highly elliptical orbit, the satellite has long dwell time over one area, but at certain times when the satellite is on the high speed portion of the orbit, there is no coverage over the desired area.

Solution

• We could have two satellites on similar orbits but timed to be on opposite sides at any given time.
• In this way, there will always be one satellite over the desired coverage area at all times.

• If we want continuous coverage over the entire planet at all times, such as the Global Positioning System (GPS satellites are in Medium Earth Orbit though), then we must have a constellation of satellites with orbits that are both different in location and time.
• In this way, there is a satellite over every part of the Earth at any given time.

Satellite constellation (Source)

Geosynchronous Orbits (GSO)

• Another solution to the dwell time problem is to have a satellite whose orbital period is equal to the period of rotation of the earth (24 hrs) (satellite’s revolution is in sync with the earth’s rotation).
• In this case, the satellite cannot be too close to the Earth because it would not be going fast enough to counteract the pull of gravity.
• Using Kepler’s third law it is determined that the satellite has to be placed approximately 36,000 km away from the surface of the Earth (~42,000 km from the centre of the Earth) in order to remain in a GSO orbit.
• By positioning a satellite so that it has infinite dwell time over one spot on the Earth, we can constantly monitor the weather in one location, provide reliable telecommunications service, etc.
• The downside of a GSO is that it is more expensive to put and maintain something that high up.

Geostationary Orbit or Geosynchronous Equatorial Orbit (GEO)

• A geostationary orbit or geosynchronous equatorial orbit is a circular geosynchronous orbit above Earth’s equator and following the direction of Earth’s rotation.
• Because the satellite stays right over the same spot all the time, this kind of orbit is called “geostationary.”

Geostationary vs Geosynchronous

Geostationary Orbit or Geosynchronous Equatorial Orbit (GEO)	Geosynchronous Orbit
They are both geosynchronous orbits (orbital period = 24 hours).Line of sight transmission
Orbital path is circular.	Orbit is an inclined circle or an inclined ellipse.
Orbital tilt is zero.	The orbital tilt is non-zero (inclined orbit)
An observer on the ground would not perceive the satellite as moving and would see it as a fixed point in the sky	A person on a point on Earth, will see a satellite in this orbit in the same place in the sky at the same time of the day, every day.Since the orbit has some inclination and/or eccentricity, the satellite would appear to describe a more or less distorted figure-eight in the sky and would rest above the same spots of the Earth’s surface once per day.
There are a limited number of positions available (traffic jam, interference of signals due to more satellites in the same orbit and risk of damage due to space debris) in this orbit due to safety and manoeuvring limits.	There are more orbital planes and positions available to satellites using this technique
Can receive signals with a simple antenna as the satellite is in relatively same position (DTH, VSAT services).(Parabolic antenna is used to nullify the effect of atmospheric distortions)	Requires a parabolic antenna as the satellite’s position slightly changes longitudinally.
Steering the antenna is not required.	It may sometimes require steering the antenna to achieve line of sight

Medium Earth Orbits (MEO: 2000-36,000 km)

• Medium Earth Orbits (MEO) range in altitude from 2,000 kms up to the geosynchronous orbit at 36,000 km which includes part of the lower and all of the upper Van Allen radiation belts.
• The Van Allen Radiation Belt is a region of high energy charged particles moving at speeds close to that of light encircling the Earth which can damage solar cells, circuits, and shorten the life of a satellite or spacecraft.
• Practical orbits therefore avoid these regions.

Polar Orbits (PO)

• Satellites in these orbits fly over the Earth from pole to pole in an orbit perpendicular to the equatorial plane.
• This orbit is used in surface mapping and observation satellites since it allows the orbiting satellite to take advantage of the earth’s rotation below to observe the entire surface of the Earth as it passes below.
• Pictures of the Earth’s surface in applications such as Google Earth come from satellites in polar orbits.

Sun-synchronous orbits (SSO)

• Polar orbit and sun-synchronous orbits are low earth orbits.
• Sun-synchronous orbit is a near polar orbit in which the satellite passes over any given point of the planet’s surface at the same local mean solar time.
• When a satellite has a sun-synchronous orbit, it means that the satellite has a constant sun illumination.
• Because of the consistent lighting, the satellites in sun-synchronous orbit are used for remote sensing applications (image the Earth’s surface in visible or infrared wavelengths) like imaging, spying, etc.

Parking Orbit

• It is not always possible to launch a space vehicle directly into its desired orbit.
• The launch site may be in an inconvenient location or the launch window may be very short.
• In such cases the vehicle may be launched into a temporary orbit called a parking orbit.
• The parking obit provides more options for realising the ultimate orbit.
• For manned space missions the parking orbit provides an opportunity to recheck the systems.

Hofmann transfer orbit

• The transfer orbit is the orbit used to break out of the parking orbit and break into the geosynchronous or geostationary orbit.

Geosynchronous transfer orbit (GTO)

• A geosynchronous transfer orbit is a Hohmann transfer orbit — an elliptical orbit used to transfer between two orbits in the same plane — used to reach geosynchronous or geostationary orbit.

Escape velocity

• Escape velocity is the minimum launch velocity (assuming the object is launched straight up) required for an object to escape earth’s gravitational pull (it doesn’t fall back to earth).
• One condition is that once launched the object is not supplied with any additional energy nor hindered by external force (like atmospheric drag) other than earth’s gravity.
• The escape velocity required for an object to escape earth’s gravitational pull is ~11.2 m/s (40,000+ kmph).
• It is neither feasible (atmospheric friction will turn it into ash) nor desirable (cannot place satellites in desired orbit) to launch rockets at escape velocity.

Polar Satellite Launch Vehicle (PSLV)

• PSLV is an indigenously-developed expendable launch system.
• PSLV was developed in 1990s by ISRO to place satellites (mostly remote sensing satellites) in polar and near polar (e.g. sun-synchronous orbit) Lower Earth Orbits.
• However, over the last decade, several PSLV missions were successful in sending satellites towards geosynchronous transfer orbit.
• E.g. Chandrayaan-1 – 2008 and Mars Orbiter Mission or Mangalyaan – 2014 were launched using PSLV.
• PSLV can fly in different configurations depending on the mass of its payload and the target orbit.
• These configurations vary the number and type of solid rocket boosters attached to the rocket’s first stage, while the four core stages remain the same across all configurations.
• PSLV’s first stage and third stage are solid-fuelled stages.
• PSLV’s second stage and forth stage are liquid-fuelled stages.
• The second stage engine, Vikas, is a derivative of France’s Viking engine.
• The PSLV-C (PSLV Core Alone) version of the rocket does not use additional boosters, while the PSLV-DL, PSLV-QL and PSLV-XL use two, four and six boosters respectively.

The Workhorse of India’s space program

• PSLV earned its title ‘the Workhorse of ISRO’ through consistently delivering various satellites to Low Earth Orbits, particularly the IRS (Indian Remote Sensing) series of satellites.
• PSLV Payload Capacity to SSO: 1,750 kg
• PSLV Payload Capacity to Sub-GTO: 1,425 kg
• In forty-seven launches to date, PSLV has achieved success forty-four times.
• Despite the failure of its maiden flight, PSLV went on to record thirty-six consecutive successful launches from 1999 to 2017.
• PSLVs were used to place the IRNSS satellite constellation (3 in GEO and 4 in GSO) in orbit.

Geosynchronous Satellite Launch Vehicle (GSLV)

• GSLV is also an expendable launch system.
• The GSLV project was initiated to launch geosynchronous satellites (most of them are heavy for PSLV).
• GSLV uses solid rocket booster and the liquid-fuelled Vikas engine, similar to those in PSLV.
• GSLV has solid-fuelled first stage, liquid-fuelled second stage and a cryogenic third stage.
• A Cryogenic rocket stage is more efficient and provides more thrust.
• However, cryogenic stage is technically a very complex system due to its use of propellants (liquid oxygen ― minus183 °C and liquid hydrogen ― minus 253 °C) at extremely low temperatures.
• India had to develop cryogenic technology indigenously as the US objected to Russia’s involvement citing Missile Technology Control Regime (MTCR) May 1992.
• A new agreement was signed with Russia for cryogenic stages with no technology transfer.
• GSLV rockets using the Russian Cryogenic Stage (CS) are designated as the GSLV Mk I.
• GSLV rockets using the indigenous Cryogenic Upper Stage (CUS) are designated the GSLV Mk II.
• GSLV Payload Capacity to LEO: 5,000 kg
• GSLV Payload Capacity to GTO: 2,500 kg
• GSLV’s primary payloads are heavy communication satellites of INSAT class (about 2,500 kg) that operate from Geostationary orbits (36000 km) and hence are placed in Geosynchronous Transfer Orbits by GSLV.
• The satellite in GTO is further raised to its final destination by firing its in-built on-board engines.

Geosynchronous Satellite Launch Vehicle Mark III (GSLV-III)

• GSLV-III is designed to launch satellites into geostationary orbit and is intended as a launch vehicle for crewed missions under the Indian Human Spaceflight Programme.
• The GSLV-III has a higher payload capacity than GSLV.
• GSLV-III Payload Capacity to LEO: 8,000 kg
• GSLV-III Payload Capacity to GTO            : 4000 kg

Chandrayaan-2

• Chandrayaan-2 has three modules namely Orbiter, Lander (Vikram) & Rover (Pragyan).
• Chandrayaan 2 will be launched using GSLV Mark III rocket.
• GSLV MK-III is a three-stage launch vehicle designed to carry four-tonne class satellites into Geosynchronous Transfer Orbit (GTO). (The Chandrayaan-1 was launched on board a PSLV).
• The GSLV Mark III rocket will first launch the spacecraft into an Earth Parking Orbit (170 km X 40,400 km).
• Then the orbit will be enhanced until the spacecraft can reach out to the Lunar Transfer Trajectory.
• On entering the moon’s sphere of influence, it will be eased into a circular orbit (100 km X 100 km).
• Subsequently, Lander will separate from the Orbiter (100 km orbit) & soft land close to lunar South Pole.
• The Rover will be carrying out scientific experiments on the lunar surface.
• The instruments will collect scientific information on lunar topography, mineralogy, elemental abundance, lunar exosphere & signatures of hydroxyl & water-ice.
• The 3.84 lakh km journey will take five days, but the spacecraft must orbit the moon for about 28 days before the lander separates itself from the orbiter.
• The mission life of the Orbiter is one year, & the rover has an expected life of 14 Earth days (one lunar day = 14 earth days; after 14 days it will be lunar night & hence the rover will be deprived of solar power).
• If the landing is successful, it will make India only the fourth country to soft-land on the lunar surface.
• The erstwhile Soviet Union, the U.S & China are the only countries to have achieved lunar landings.

Source & Credits: The Hindu

Gaganyaan Mission

• Gaganyaan is the 1^st human space flight programme of ISRO.
• Under this mission Indian astronauts will go into space (low earth orbit) by 2022.
• This will be done by using its own capabilities. 
• This crewed orbital spacecraft is expected to carry 3 peoples into space for 7 days.
• A GSLV-Mk III launch vehicle will lift them to their orbit.
• India has signed agreements with Russia & France for cooperation on the Gaganyaan mission.
• Recently Human space flight centre was inaugurated to coordinate Indian human space flight programme, it will also be responsible to implement the project.
• Until now, only Russia, US & China have managed to send manned missions to outer space.

Challenges for Astronauts

• The astronauts will have to adapt to the change in gravitational field. 
• The change in gravity affects hand-eye & head-eye coordination.
• Bones may lose minerals adding to the risk of osteoporosis related fractures.
• Lack of exercise & improper diet make them lose muscle strength & cause develop vision problems.
• Once they are in space, astronauts will receive over 10 times more radiation than what people are subjected to on earth. 
• It can cause cancer, nervous system damage & trigger nausea, vomiting, & anorexia & fatigue.
• Without pressure, human blood heats up.
• Despite the training, behavioural issues may crop up due to isolation leading to depression.

GEMINI: Gagan Enabled Mariner’s Instrument for Navigation & Information

• For dissemination of information on disaster warnings, Potential Fishing Zones (PFZ) and Ocean States Forecasts (OSF) to fishermen, GOI launched GEMINI device and mobile application.

The need for GEMINI

• PFZ forecasts, developed by INCOIS, will provide advisories on PFZ to fishermen 3 days in advance.
• Ocean State Forecasts include the forecasts on winds, waves, ocean currents, water temperature, etc.
• However, PFZ & OSF advisories do not reach fishermen when they move 10-12 km away from the coast.
• The communication gap puts the life & property of those involved in deep sea fishing in Indian Ocean at risk.
• To overcome this difficulty, GEMINI portable device was developed.

How GEMINI works?

• GEMINI device utilizes the GAGAN system to transmit the PFZ, OSF and disaster warnings to user’s cell phone.
• The GEMINI app on the cell phone decodes the signals from GEMINI device and alerts the user on imminent threats like cyclones, high waves, strong winds along with PFZ and search and rescue mission.

GPS Aided Geo Augmented Navigation (GAGAN)

• GAGAN is a Satellite Based Augmentation System (SBAS) for the Indian Airspace.
• It provides the additional accuracy and integrity necessary for all phases of flight.
• ISRO and Airports Authority of India (AAI) have implemented the GAGAN project.
• GAGAN is operational through GSAT-8, GSAT-10 satellites & GSAT-15 satellites.
• The system is inter-operable with other international SBAS systems like US-WAAS, European EGNOS, etc.
• GAGAN footprint extends from Africa to Australia.
• GAGAN though primarily meant for aviation, will provide benefits beyond aviation to many other segments such as intelligent transportation, maritime, railways, etc.

Source: ISRO

Satellite-based Augmentation Systems (SBAS)

• The performance of Global Navigation Satellite Systems (GNSSs) can be improved by regional Satellite-based Augmentation Systems (SBAS), such as GAGAN.
• SBAS improves the accuracy and reliability of GNSS information by correcting signal measurement errors.

Examples of Satellite-based Augmentation Systems (SBAS)

• USA: Wide Area Augmentation System (WAAS)
• EU: European Geostationary Navigation Overlay Service (EGNOS)
• India: GPS and GEO Augmented Navigation (GAGAN)

Examples of Global Navigation Satellite Systems (GNSSs)

• Global Positioning System (United States)
• GLONASS (Russia)
• Galileo (EU)
• BeiDou (China)
• IRNSS ― NAVIC (India)

India’s Communication Satellites

• Indian National Satellite System (INSAT)
• GSATs (Geo synchronous Satellites)

Indian National Satellite System (INSAT)

• INSAT, is a series of multipurpose geostationary satellites launched by ISRO.
• Established in 1983 with commissioning of INSAT-1B, the INSAT system with more than 200 transponders in the C, Extended C and Ku-bands provides services to telecommunications, television broadcasting, satellite newsgathering, weather forecasting, disaster warning and Search and Rescue operations.

GSATs (Geo synchronous Satellites)

• The new generation INSATs are now named as GSATs (Geo synchronous Satellites).
• The GSAT satellites are used for digital audio, data and video broadcasting.

Transponder

• In a communications satellite, a satellite transponder receives signals over a range of uplink frequencies, usually from a satellite ground station.
• The transponder amplifies them and re-transmits them on a different set of downlink frequencies to receivers on Earth, often without changing the content of the received signal or signals.

Satellite frequency bands

Source and Credits: ESA

L-band (1–2 GHz)

• Used by Global Positioning System (GPS) carriers and satellite mobile phone communication devices.

S-band (2–4 GHz)

• Used by weather radar, surface ship radar, and some communications satellites.

C band (4–8 GHz)

• Used for satellite communications, for full-time satellite TV networks.
• Ssed in areas that are subject to tropical rainfall (less susceptible to signal degradation than Ku band).
• Because of the low frequencies, C band waves have longer wavelengths.
• Because of bigger wavelengths, a bigger dish is required to receive such frequencies.

X-band (8–12 GHz)

• Primarily used by the military.
• Sub-bands are used in civil, military and government institutions for weather monitoring, air traffic control, maritime vessel traffic control, defence tracking and vehicle speed detection for law enforcement.

Ku-band (12–18 GHz)

• Used for satellite communications, most notably the downlink used by DTH television.
• Because of the higher frequencies, Ku band waves have shorter wavelengths.
• Shorter wavelengths mean that you need a smaller dish to receive these frequencies.

K-band (18–26 GHz)

• Due to the 22 GHz water vapor absorption line this band has high atmospheric attenuation and is only useful for short range applications.

Ka-band (26–40 GHz)

• Used for communications satellites with high-resolution, close-range targeting radars on military aircraft.

Why are the Geostationary satellites launched from east coast in eastward direction and from locations that are close to the equator?

• If you observe the location of all the launch centers like Sriharikota, Kennedy Launch Center (USA: Florida), Guiana Space Centre etc., all are located on the East coast of the continent and are close to the equator.
• The location of Kennedy Space Center and Satish Dawan Space Center makes them particularly vulnerable to tropical cyclones and other weather “events”.
• However, they are good locations for rocket launches as thay are on the east coast and close to the equator.
• Also, the islands are less densely populated, making them safer to carry out launches.

Why in eastward direction?

• As the earth rotates from west to east, a satellite launched in the east direction will get an initial boost equal to the velocity of Earth surface.

Why at equator?

Reason 1:

• Earth’s rotational velocity is maximum at the equator (on earth, centrifugal force is maximum at the equator).
• Hence for maximum initial boost, the launch site needs to be closer to the equator.
• Anything on the surface of the Earth at the equator is already moving at 1670 kilometers per hour (rotational velocity of earth).
• But this benefit can be taken only for such satellites which are placed in geo-stationary orbit or which circle the Earth parallel to the equator.

Reason 2:

• Communication satellites are put into geostationary orbit above the equator with zero inclination to the equatorial plane.
• The ideal place to launch to geostationary orbit is, obviously, on the equator.
• Equatorial launches only require the vehicle to bring the payload to orbital speed and do not require inclination changes.
• For launches that are not on the equator, the vehicle must perform a complex adjustment burn in the GTO (geostationary transfer orbit) phase of the mission to bring the vehicle an inclination of 0º.

• The vehicle first reaches low earth orbit (green circle), then makes a burn to geostationary transfer orbit (the red ellipse), then makes a second burn to circularize the orbit into geostationary orbit (orange circle).
• When a vehicle is launched from the equator, the three orbits shown are planar (they lie in the same plane).
• If the vehicle is launched from a non-equatorial launch site, the green circle and the orange circle are non-planar, thus requiring the red ellipse to bridge the two orbits (More fuel will be required = high costs).
• This maneuver consumes propellant and thus decreases the payload. That’s another reason why equatorial launches (or as close as possible) are preferred.

What about polar satellites (remote sensing and earth observation satellites)?

• Such satellites are usually communication satellites or satellites used for scientific research such as ISS.
• There are other satellites which are placed in polar orbits moving across the equator in north south direction and used mainly for mapping or sometimes for spying.
• Such satellites are generally launched in south ward or north ward direction and therefore cannot take advantage of the Earth’s rotation.

Why are launch sites on the east coast?

• Launching stations are generally located near eastern coastline so that, just in case of failure of the launch, the satellite does not fall on built-up hinterland.

NavIC Navigation System

Countries are working on building their navigation systems

• GPS è owned by the US government and operated by the US Air Force.
• GLONASS è Russia
• Galileo è European Union (EU)
• BeiDou è China
• Quasi-Zenith Satellite System (QZSS) è Japan (regional navigation system still under construction)
• India’s navigation system is called Navigation with Indian Constellation (NavIC) — previously known as Indian Regional Navigation Satellite System (IRNSS).

Link: Source and Credits

NavIC (IRNSS)

•  IRNSS is an independent regional navigation satellite system being developed by India (ISRO).
• It is designed 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.
• IRNSS is a regional and not a global navigation system.
• An Extended Service Area lies between primary service area and area enclosed by the rectangle from-
• Latitude 30 deg South to 50 deg North,
• Longitude 30 deg East to 130 deg East.
• IRNSS will 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 better than 20 m in the primary service area.
• Some applications of IRNSS are:
• Terrestrial, Aerial and Marine Navigation
• Disaster Management
• Vehicle tracking and fleet management
• Integration with mobile phones
• Precise Timing
• Mapping and Geodetic data capture
• Terrestrial navigation aid for hikers and travellers
• Visual and voice navigation for drivers
• ISRO has built a total of nine satellites (earlier 7) in the IRNSS series of which eight are currently in orbit.
• Three of these satellites are in geostationary orbit (GEO) while the remaining in geosynchronous orbits (GSO) that maintain an inclination of 29° to the equatorial plane.
• The IRNSS constellation was named as “NavIC” (Navigation with Indian Constellation).

Link: Source and Credits

Additional Reading How Navigation System Works? Satellite Navigation is based on a global network of satellites that transmit radio signals. The working of the navigation system is based on the ‘trilateration’ & ‘triangulation’ principle.A navigation system device uses data from satellites to locate a specific point on the Earth in a process called trilateration. To trilaterate, a GPS receiver measures the distances to satellites using radio signals. Trilateration is similar to triangulation, which measures angles, depicted in this illustration. Link: Source and Credits Triangulation Triangulation works with line-of-sight.Triangulation Measures Angles, Not Distance. Trilateration Three signals put you at one of two points on that circle—and that’s usually enough to figure out where you are, because one of the points might be up in the air or in the middle of the ocean. With four signals, you know your position precisely. Finding your location this way is called trilateration.GPS Receivers Use Trilateration. Link: Source and Credits Link: Source and Credits

Private Sector Participation in Space Sector

PIB | GS3 > Space Technology

• Context: Government has created Indian National Space, Promotion & Authorization Centre (INSPACe), under Department of Space to encourage the private sector for their participation in Space Sector.

IN-SPACe

• Private players will also be able to use ISRO infrastructure through INSPACe.
• The role of New Space India Limited (NSIL) in the post reformed space sector would be to build launch vehicles, providing launch services, build satellites, providing space-based services, technology transfers, etc.
• The broad areas and sectors covered by private companies are- providing materials, mechanical fabrication, electronic fabrication, system development, integration, etc.
• IN-SPACe is supposed to be a facilitator, and also a regulator.
• It will act as an interface between ISRO and private parties, and assess how best to utilise India’s space resources and increase space-based activities.
• IN-SPACe will have a Chairman, technical experts for space activities, Safety expert, experts from Academia and Industries, members from PMO and MEA of Government of India.
• IN-SPACe is the second space organisation created by the government in the last two years.
• In the 2019 Budget, the government had announced the setting up of a New Space India Limited (NSIL), a public sector company that would serve as a marketing arm of ISRO.
• Its main purpose is to market the technologies developed by ISRO and bring it more clients that need space-based services.
• That role, incidentally, was already being performed by Antrix Corporation, another PSU working under the Department of Space, and which still exists.

About ISRO

• The Indian Space Research Organisation is the space agency of the Government of India and has its headquarters in the city of Bangalore (also known as Bengaluru).
• Its vision is to “harness space technology for national development while pursuing space science research & planetary exploration”.
• The Indian National Committee for Space Research (INCOSPAR) was established by Jawaharlal Nehru under the Department of Atomic Energy (DAE) in 1962, with the urging of scientist Vikram Sarabhai recognising the need in space research.
• INCOSPAR grew and became ISRO in 1969, also under the DAE.
• ISRO built India’s first satellite, Aryabhata, which was launched by the Soviet Union on 19 April 1975.

Organisation Structure and Facilities

• ISRO is managed by the Department of Space (DoS) of the Government of India. DoS itself falls under the authority of the Space Commission and manages the following agencies and institutes:
• Indian Space Research Organisation
• Antrix Corporation – The marketing arm of ISRO, Bangalore.
• Physical Research Laboratory (PRL), Ahmedabad.
• National Atmospheric Research Laboratory (NARL), Gadanki, Andhra pradesh.
• New Space India Limited – Commercial wing, Bangalore.
• North-Eastern Space Applications Centre (NE-SAC), Umiam.
• Semi-Conductor Laboratory (SCL), Mohali.
• Indian Institute of Space Science and Technology (IIST), Thiruvananthapuram – India’s space university.