SPACE TECHNOLOGY

Difference between air-space and space

 

1. ORBITS AND SATELLITES

1.1 Type of satellites

1.2 Types of orbits

Polar Orbit

Sun Synchronous Orbit or Sun Synchronous Polar Orbit (SSO or SSPO)

Equatorial orbit

Geosynchronous orbit (GSO) or Earth Synchronous orbit

Geostationary orbit or geosynchronous equatorial orbit (GEO)

Geosynchronous or Geostationary Transfer Orbit (GTO)

Low Earth Orbit (LEO)

Medium Earth orbit (MEO)

High Earth orbit

 

2. SATELLITE LAUNCH VEHICLES

Payload

Fuel and Oxidiser

Engine

Strap-on Motors

PSLV: Polar Satellite Launch Vehicle

GSLV: Geosynchronous Satellite Launch Vehicle

Reusable launch vehicle

 

3. SPACE PROBE

Space Probes by NASA

Other space probes

Chandrayaan-1, 2008-2009

Chandrayaan-2, July-2019

ASTROSAT, 2015

Mangalyaan or Mars Orbiter Mission (MOM)

Aditya L1, 2019

Gaganyaan Mission

 

4. RELATED CURRENT AFFAIRS

Anti-satellite (ASAT) missile

IRNSS or NAVIC

Web Mapping Service

Outer Space Treaty, 1967

Laser Interferometer Space Antenna (LISA) mission

GSAT-11

 

 

 

SPACE TECHNOLOGY

Indian Space Programme was started in early 60s by Pt. Jawaharlal Nehru and Vikram Sarabhai under the DAE.

Indian Space Research Organization (ISRO) was established in 1969.

Antrix Corporation, Bangalore is ISRO’s commercial arm.

 

Difference between air-space and space

  • Air space is controlled by individual country. Space is Global common.
  • Air space is used for air transport.

 

1. ORBITS AND SATELLITES

  • 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. – NASA.
  • Planets, comets, asteroids and other objects in the solar system orbit the sun.
  • After having lived out their useful lives, satellites become space debris.
  • Most of the objects orbiting the sun move along or close to an imaginary flat surface. This imaginary surface is called ecliptic plane.
  • An orbit has a balance of two forces: Centripetal force (due to satellite’s velocity) and earth’s gravitation force. An artificial satellite is always falling towards earth. But, it does not fall down due to the balance of these two forces.

 

1.1 Type of satellites

  • Natural satellite: like Earth or moon. Many planets have moons orbiting them.
  • Man-made satellite: like International Space Station. In 1957, Soviet Union launched the world’s first artificial satellite, Sputnik 1.
  • Communication satellites: all INSATs (Except INSAT 3D), GSAT, EDUSAT.
  • Navigation satellites (7): IRNSS
  • Space science satellites (2): MOM, ASTROSAT
  • Earth observation satellites (12): INSAT 3D and all others.

 

1.2 Types of orbits

 

Polar Orbit

  • It has an inclination of 900 to the equator. In a polar orbit, a satellite passes above both the north and south poles.
  • This allows the satellite to observe every part of the Earth. But, a location cannot be under continuous surveillance.
  • Hence, polar orbit is suitable for earth mapping satellites, weather satellites, communication satellites, remote sensing satellites, reconnaissance or spy satellites and surveillance
  • Satellite is launched from higher latitude.

 

Sun Synchronous Orbit or Sun Synchronous Polar Orbit (SSO or SSPO)

  • This is a special case of polar orbit.
  • This orbit allows a satellite to pass over a spot on the Earth at the same time of day.
  • The satellite is always at the same angle to the Sun. Since there are 365 days in a year and 360 degrees in a circle, the satellite has to shift its orbit by one degree per day (approximately).
  • These are Low Earth Orbit.
  • This orbit can place a satellite in constant sunlight, which allows the solar panels to work continually.
  • Advantage: A location can be under continuous surveillance.

 

Equatorial orbit

  • It is an orbit that lies close to the equatorial plane. Such an orbit has an inclination near 0°.
  • A satellite must be launched from a place close to the equator. E.g. French Guiana, Thumba.
  • Launches directly into equatorial orbit eliminate the need for costly adjustments to a spacecraft’s trajectory.

Thumba Equatorial Rocket Launching Station (TERLS) at VSSC

  • Very close to magnetic equator of the Earth, making it ideal to conduct atmospheric research.
  • One of the farthest points from Pakistan and China.

 

Geosynchronous orbit (GSO) or Earth Synchronous orbit

  • It has a period of revolution equal to period of rotation of earth, one sidereal day. It is synchronized with the Earth’s rotation.
  • Satellites are typically launched in an eastward direction. A circular geosynchronous orbit is 35,786 km above the Earth’s surface.
  • The orbit is tilted with respect to the plane of the equator.
  • An object in geosynchronous orbit returns to exactly the same position in the sky after one sidereal day.

Notes: solar day: the time between successive noons. It is 24 hours for earth.

Sidereal day: the time in which Earth rotates once around its axis 360 degrees. It is ~4 minutes shorter than solar day. (23 hours, 56 minutes, 4 seconds).

 

 

Geostationary orbit or geosynchronous equatorial orbit (GEO)

  • It is a special case of geosynchronous orbit, which has a circular orbit in Earth’s equatorial plane.
  • A geostationary orbit is a particular type of equatorial orbit.
  • A circular geosynchronous orbit is 35,786 km above Earth’s equator. It yields an orbital period of 24 hours.
  • The satellite has very high Speed, so that its orbit matches the Earth’s rotation.
  • An object in such an orbit appears motionless, looks like fixed in the sky to ground observers or to its
  • Application: Communications satellites and weather E.g. IRNSS: Three satellites are in geostationary orbit over the Indian Ocean.

 

Geosynchronous or Geostationary Transfer Orbit (GTO)

  • It is a highly elliptical Earth orbit wit elliptical orbit used to transfer between two circular orbits of different radii. It has an apogee (high point) of 35,784 km.
  • A high thrust launch vehicle helps to escape Earth’s atmosphere and to maximize total mass.

 

Low Earth Orbit (LEO)

  • It is placed near to the Earth at an altitude of 2,000 km.
  • Application: All crewed space stations to date, and majority of the satellites, are in LEO. The International Space Station is in LEO.
  • Gaganyaan, 2022 will be the first human spaceflight mission of India.

 

Medium Earth orbit (MEO)

  • A region of space above low Earth orbit and below geosynchronous orbit.
  • The most common altitude is approximately 20,000 kilometres. It yields an orbital period of 12 hours.
  • Application: navigation satellites with global coverage. g. Global Positioning System (GPS), USA. Glonass, Russia. Galileo, EU. BeiDou, China.

Note: If the satellite is in a polar, sun-synchronous, or equatorial orbit, its orbital altitude may be medium or low.

 

 

High Earth orbit

  • Its altitude is above that of a geosynchronous orbit i.e. 35,786 kilometres.
  • The orbital periods are greater than 24 hours.

 

 

2. SATELLITE LAUNCH VEHICLES

 

Payload

  • It is the carrying capacity of an aircraft or launch vehicle, usually measured in terms of weight.

Fuel and Oxidiser

  • PS2: Vikas engine, Earth storable liquid rocket engine, UDMH (Fuel) + N2O4 (Oxidiser)
  • PS3: Solid fuel = HTPB.
  • PS4: 2 engines, MMH + MON

Engine

Principle: Based on Newton’s Third Law of Motion.

  • Jet engines and rocket engines work on the same principle.
  • Jet engines get the oxygen to burn fuel from the These have two openings -an intake and an exhaust nozzle.
  • Rockets carry their own oxygen, which allows them to operate in space. These have one opening -an exhaust nozzle.

Vikas Engine

  • The Vikas (from initials of VIKram Ambalal Sarabhai )
  • It is a family of liquid fuelled rocket engines.

Kaveri Engine

  • It is a jet engine.
  • Originally intended for HAL Tejas.
  • Failed to satisfy the technical requirements.

 Cryo-engine

  • It uses a cryogenic fuel and oxidizer. i.e. its fuel and oxidizer are gases liquefied and stored at very low temperatures.
  • liquid hydrogen (LH2) fuel and the liquid oxygen (LOX) (liquid H2 + O2 )
  • The C25 is powered by CE-20, India’s largest cryogenic engine, designed and developed by the Liquid Propulsion Systems Centre.
  • India is among six nations — apart from the US, Russia, France, Japan and China — to possess cryogenic engine technology.

Strap-on Motors

  • Along with the solid rocket motor core of the first stage, strap-ons these are required to extract maximum thrust out of the initial stages.
  • PSLV: In PSLV-XL and PSLV-G, there are HTPB based solid Strap-on motors. There are no strap-on motors in PSLV-CA (core alone version).
  • GSLV: There are 4 liquid strap-on motors, powered by one Vikas engine

 

 

PSLV: Polar Satellite Launch Vehicle

  • Before the advent of PSLV in 1993, launching a satellite into sun-synchronous orbits service was commercially available only from Russia.
  • It was developed to launch earth observation satellites. g. Indian Remote Sensing (IRS) satellites into sun-synchronous orbits.
  • PSLV is an expendable medium-lift launch vehicle.

Capacity

  • It can launch up to 1,750 kg payload to Sun-Synchronous polar orbits (600 km approx).
  • It is also used to launch a payload with lower lift-off mass up to 1400 Kg into Geostationary Transfer Orbit (GTO). It ultimately launches a satellite into Geosynchronous and Geostationary orbits. E.g. for IRNSS.

Stages

  • Four stages, alternating solid and liquid stages.
  • PS1: It is a Solid fuel (HTPB) powered stage. It provides the launcher the high thrust that is required for lift off. PSLV-G and PSLV-XL are Strap-on versions.
  • PS2: It is earth storable liquid fuel powered stage. Vikas engine is used.
  • PS3: It is a Solid fuel powered stage, which provides high thrust after the atmospheric phase of the launch.
  • PS4: It is a Solid fuel (MMH + MON) powered stage. 2 engines are used. The purpose of this stage is to correct the trajectory.

Some notable payloads launched by PSLV

  • India’s first lunar probe Chandrayaan-1, India’s first interplanetary mission Mangalyaan and India’s first space observatory Astrosat, India’s indigenous navigation system IRNSS

 

GSLV: Geosynchronous Satellite Launch Vehicle

  • GSLV is designed mainly to deliver the communication satellites to the Geosynchronous Transfer Orbit (GTO).
  • GSLV Mark II (GSLV Mk II): It is a three stage medium lift launch vehicle. (First Flight: 2001). It uses CE-7.5, India’s first cryo engine.
  • GSLV Mk-III: It is a three stage heavy lift launch vehicle with an indigenous cryogenic upper stage engine (C25).

It has two solid fuel strap-on engines in first stage. It uses CE20, India’s largest cryogenic engine.

It will be the launch vehicle for Gaganyaan to LEO.

Capacity

  • GSLV Mk-II: It can launch up to 2,500 kg payload to GTO (Geosynchronous Transfer Orbit) and up to 5,000 kg to LEO (low earth orbit).
  • GSLV Mk-III: It has been designed to carry heavier communication satellites weighing up to 4000 kg to GTO, and 8,000 kg to LEO.

Stages

  • Stage 1: The first stage of GSLV is derived from the PS1 of PSLV. Strap-ons are required to extract maximum thrust out of the initial stages.
  • Stage 2: The second stage was derived from the PS2 of PSLV, where the Vikas engine has proved its reliability.
  • Stage 3: Cryogenic Upper Stage (CUS- Mk II, C25- Mk III): It imparts a high velocity to the payload to achieve escape velocity.

Some notable payloads launched by GSLV

  • Communication satellites of INSAT class, EDUSAT and GSAT (all in Geostationary orbits)

Problem: All INSATs were launched from outside India.

Reusable launch vehicle

A few companies are developing reusable launch systems intended to cut costs. Such as the SpaceX Falcon 9.

 

 

3. SPACE PROBE

It is a robotic spacecraft that does not orbit Earth, but explores into outer space, orbits or lands on other planetary bodies. E.g. Moon or Mars.

Space Probes by NASA

  • Cassini–Huygens: (NASA+ESA+..)To study Saturn, along with its ringed system and moons. In 2017, the probe was de-orbited and burned up in Saturn’s atmosphere.
  • New Horizons: First probe
  • Dawn: First spacecraft to visit protoplanet (4 Vesta). Currently orbiting Ceres is the largest object in the asteroid belt that lies between the orbits of Mars and Jupiter.
  • Mars Climate Orbiter, Mars Polar Lander: planet Mars.
  • Juno: planet Jupiter.
  • Messenger: planet Mercury.
  • Pioneer 10 and 11, Voyager 1 and 2: Interstellar probes: Beyond the Solar System.
  • Apollo 11: the first crewed mission of USA to land on the Moon (1969).
  • Themis: to study auroras.

 

Other space probes

  • Luna 2: First man-made object to reach the surface of the Moon (1959).
  • Selene: Japanese lunar orbiter.
  • Chang’e 4, 2019: first soft landing on the far side of the Moon [Chang’e: Chinese Moon goddess]

 

Chandrayaan-1, 2008-2009

  • It was India’s first lunar probe. It made India the fourth country to place its flag on the Moon.
  • Launched from PSLV-XL C11 rocket, from SDSC, Sriharikota.
  • The probe struck near Shackleton crater, known as Jawahar Point.
  • It stopped working in 2009 due to failure of the star sensors and poor thermal shielding. In 2016, NASA used ground-based radar systems to relocate it in its lunar orbit.

 

Chandrayaan-2, July-2019

  • It will be is India’s second lunar exploration mission, and is to be launched from GSLV Mk III.
  • If successful, Chandrayaan-2 will be the India’s first mission to land near the lunar south-pole. Earlier Chang’e 4 has landed here.
  • Chandrayaan-2 will make India the 4th country to soft-land on the moon, only after US, USSR and China. Soft-landing prevents damaging vehicle.
  • It has three modules namely Orbiter, Lander (Vikram) & Rover (Pragyan). The rover data will be relayed through Chandrayaan-2 orbiter.

 

ASTROSAT, 2015

  • Astrosat is India’s first dedicated multi wavelength space observatory. (space telescope).
  • It was launched from PSLV-XL vehicle at SDSC, with a lift-off mass of 1500 kg into a near-Earth, equatorial orbit.
  • It is an IRS-class satellite (Indian Remote Sensing).
  • A number of space agencies have become successful to send a space observatory.

 

Mangalyaan or Mars Orbiter Mission (MOM)

  • It is orbiting Mars since 2014. It is “technology demonstrator” for interplanetary mission.
  • It is India’s first interplanetary mission. ISRO became fourth space agency to reach Mars, after Roscosmos (Russia), NASA (USA), and the European Space Agency.
  • India became the first nation to do so in first attempt, and is the first Asian nation to reach Mars orbit.
  • The lifted-off from Satish Dhawan Space Centre using a PSLV C25 rocktet in 2013.
  • The total cost of the mission was ₹450 Crore, the least-expensive Mars mission to date.

 

Aditya L1, 2019

It is India’s first solar mission.

It will be placed in a halo orbit around a vantage point in space known as L1 Lagrange point. The Aditya-L1 mission will be inserted in a halo orbit around the L1, which is about 1.5 million km from the Earth.

The 1,500 kg class satellite, carries a total of seven payloads, including the main payload- Visible Emission Line Coronagraph (VLEC).

Objective:

  • First satellite to study the magnetic field of the sun’s corona.
  • To study that why the deeper layer of the sun (photosphere) is at much lower temperature than the corona.
  • To study space weather, solar wind, etc. to Pluto.

Lagrange point

  • It is a point of equilibrium where combined gravitational forces of two bodies equal the centrifugal force felt by much smaller body. For example, Earth and sun.
  • The sun can be viewed sun without any occultation or eclipses.

 

Gaganyaan Mission

It will be first Indian human spaceflight mission into the space by 2022.

  • It will use GSLV Mk-III.
  • Experiments are already done and are successful. such as Space Capsule Recovery Experiment (SRE-2007), Crew module Atmospheric Reentry Experiment (CARE-2014).
  • ISRO also recently unveiled a space capsule (crew module) and Space suit prototype.
  • Aim: development of newer technologies, increased understanding of human body functioning, understanding of effects of microgravity and cosmic radiation on bioorganisms etc.
  • Will be implemented by ISRO Human Space Flight Centre (HSFC), Bengaluru.

 

 

 

4. RELATED CURRENT AFFAIRS

 

Anti-satellite (ASAT) missile

  • ASATs are space weapons designed to destroy satellites for strategic military purposes.
  • India recently became the fourth country, only next to the United States, Russia, and China, to successfully demonstrate this capability.
  • Mission Shakti: In March 2019, India destroyed a “live satellite” in Low Earth orbit. Developed by DRDO, It was launched from Integrated Test Range (ITR) in Chandipur, Odisha and targeted Microsat-R.
  • Indian ASAT program utilized technologies from Indian Anti-Ballistic missiles defence system. Prithvi Air Defence (PAD) is India’s first exo atmospheric interceptor, similar to THAAD, an American anti-missile system.
  • No ASAT system has yet been utilised in warfare.

 

IRNSS or NAVIC

  • Indian Regional Navigation Satellite System or NAVigation with Indian C
  • Rationale to develop: American Global Positioning System (GPS) refused to provide services during the Kargil War in 1999.
  • It provides real-time positioning and timing services.
  • It covers India and a region extending 1,500 km around it.
  • The system at present consists of a constellation of seven satellites, with two additional satellites on ground as stand-by. There are plans to expand these from 7 to 11.
  • Three satellites will be in geostationary orbit and four in geosynchronous orbit.

 

Web Mapping Service

  • It is the process of using the maps delivered by geographic information systems (GIS) in World Wide Web (Online).
  • It allows users to explore 2D and 3D representation of the Earth surface. e.g. Google earth, Wikimapia, Bhuvan.
  • Bhuvan browser is specifically tailored to view India, offering the highest resolution in the region.

 

Outer Space Treaty, 1967

  • Treaty on principles governing the activities of states in the exploration and use of outer space.
  • India is a signatory.

 

Laser Interferometer Space Antenna (LISA) mission

  • It is led by the European Space Agency to detect and measure gravitational waves, the tiny ripples in the fabric of space-time.
  • LISA would be the first dedicated space-based gravitational wave detector.

 

GSAT-11

  • It is the heaviest satellite built by ISRO. It weighs around 5855 Kg, double the size of biggest satellite built till now.
  • It was launched into circular geo-stationary orbit from French Guiana by Ariane-V Rocket of Arianespace (a joint venture of Airbus and Safran).
  • It will provide country’s Internet Broadband from space to untouched areas at throughput data rate of 16 gbps. It is part of ISRO’s high-throughout communication satellite (HTS)
  • It carries 40 transponders in Ku (32)/ Ka (8) Band. For the First time use of Ka-Band is introduced in India.

ISRO’s most powerful launcher GSLV-Mk III can launch satellite weighing up to 4000 kg only to GTO.

Ku vs Ka Band

  • Ku band ranges between 12-18 GHz while Ka Band ranges from 26.5-40 GHz.
  • It is difficult to build hardware and software for Ka Band Transponders. Most satellites today use Ku Band Transponders.