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Space Organizations/Terminology

Space Organizations in India Terminologies Related to the Space Science

Space Organizations

1. Vikram Sarabhai Space Centre (VSSC)

• The VSSC at Thiruvananthapuram is the largest among the ISRO facilities for the development of satellite launch vehicles and associated technology. The centre had its beginnings as the Thumba Equatorial Rocket Launching Station (TERLS) in 1962. It was renamed in honour of Dr. Vikram Sarabhai, the father of the Indian space program.

• November 21, 1963 marked India’s first venture into space, with the launch of a two-stage Nike Apache sounding rocket from TERLS. The first rockets launched were built in United States.

• The Vikram Sarabhai Space Centre is one of the main research and development establishments within ISRO. VSSC is an entirely indigenous facility working on the development of sounding rockets, the Rohini and Menaka launchers, and the Augmented Satellite Launch Vehicle (ASLV), Polar Satellite Launch Vehicle (PSLV), Geosynchronous Satellite Launch Vehicle (GSLV) and GSLV Mk III families of launch vehicles.

• The VSSC pursues research and development in the fields of aeronautics, avionics, composites, computer and information technology, control guidance and simulation, launch vehicle design, mechanical engineering, mechanisms vehicle integration and testing, propellants polymers and materials, propulsion propellants and space ordnance, and systems reliability.

• Current focus of VSSC is on the (GSLV), the GSLV Mk III and the Reusable Launch Vehicle- Technology Demonstrator (RLV-TD).

• VSSC also has programs focused on applications of space technology including village resource centres, telemedicine, tele-education, disaster management support and outreach through Direct To Home television broadcast.

2. ISRO Satellite Centre (ISAC)
• The ISRO Satellite Centre (ISAC) is the leading centre of ISRO for design, development, fabrication and testing of all Indian made satellites. It was established in the year of 1972 as Indian Scientific Satellite Project (ISSP) in Bengaluru.

• The centre has produced more than 50 satellites including the INSAT series, the Indian Remote Sensing series, as well as the GSAT communication satellites. Organisations under the umbrella of ISAC include the Laboratory for Electro-Optics Systems (LEOS) and the ISRO Satellite Integration and Testing Establishment (ISITE).

• The LEOS is mainly responsible for research, development and production of Sensors for ISRO programmes. The ISITE houses all facilities for building a spacecraft under-one-roof. It provides necessary support for testing sub-systems and spacecraft to meet the requirements of space environment.

3. Satish Dhawan Space Centre (SDSC)/ Sriharikota High Altitude Range (SHAR)
• Satish Dhawan Space Centre (SDSC) or Sriharikota High Altitude Range (SHAR) is a rocket launch centre of ISRO. It is located in Sriharikota in Andhra Pradesh. Features like a good launch azimuth corridor for various missions, nearness to the equator (benefiting eastward launches), and large uninhabited area for a safety zone make it an ideal spaceport.

• The SHAR facility now consists of two launch pads, with the second built in 2005. The second launch pad was used for launches beginning in 2005 and is a universal launch pad, accommodating all of the launch vehicles used by ISRO. The two launch pads will allow multiple launches in a single year, which was not possible earlier.

• SHAR will be the main base for the Indian human spaceflight program. A new third launch pad will be built specifically to meet the target of launching a manned space mission by 2017.

4. Liquid Propulsion System Centre (LPSC)
• Liquid Propulsion Systems Centre (LPSC) is the lead Centre for development and realization of earth-to-orbit advanced propulsion stages for Launch Vehicles and also the in-space propulsion systems for Spacecrafts. It is involved in the development of liquid and cryogenic propulsion for launch vehicles and satellites.

• The LPSC activities and facilities are spread across its two campuses viz., LPSC Headquarters and Design Offices and Spacecraft Propulsion Systems Unit.

• LPSC is engaged in development of liquid and cryogenic propulsion stages for launch vehicles and auxiliary propulsion systems for both launch vehicles and satellites. Activities related to liquid propulsion stages, cryogenic propulsion stages and control systems for launch vehicles and spacecraft is done at Thiruvananthapuram. Precision fabrication facilities, development of transducers and integration of satellite propulsion systems are carried out at Bangalore. The developmental and flight tests along with assembly and integration are done at ISRO Propulsion Complex, Mahendragiri in Tamil Nadu.

5. Space Applications Centre (SAC)
• The SAC focuses on the design of space-borne instruments for ISRO missions and development and operationalisation of applications of space technology for societal benefits. It is engaged in the development of pay loads for communication, broadcasting, navigation, disaster monitoring, meteorology, oceanography, environment monitoring and natural resources survey.

• This includes research and development of on-board systems, ground systems and end user equipment hardware and software. Some of the achievements of the Space Applications Centre include development of communication and meteorological payloads for INSAT satellites, optical and microwave payloads for IRS satellites.

• SAC provides its infrastructure to conduct training courses to the students of the Center for Space Science and Technology Education in Asia and The Pacific (CSSTEAP). SAC has three campuses, two of which are located at Ahmedabad and one at Delhi.

6. Antrix Corporation Limited
• Antrix Corporation Limited (ACL) is a wholly owned Government of India Company, under the administrative control of Department of Space (DOS). It is the apex marketing agency under DOS with access to resources of DOS as well as Indian space industries.

• Antrix promotes and commercially markets the products and services emanating from the Indian Space Programme. In the year 2008, the Company was awarded ‘MINIRATNA’ status. The current business activities of Antrix are as follows:

a) Provisioning of communication satellite transponders to various users,
b) Providing launch services for customer satellites,
c) Marketing of data from Indian and foreign remote sensing satellites,
d) Building and marketing of satellites as well as satellite sub-systems,
e) Establishing ground infrastructure for space applications, and
f) Mission support services for satellites.

Terminology

TERMS RELATED TO THE PATH OF THE SATELLITE

1) Apogee: It is a point on the orbit where vertical distance of the satellite from the Earth’s surface is maximum. The maximum distance of the satellite from Earth’s surface is also called apogee of the orbit of the satellite.

2) Perigee: It is a point on the orbit where vertical distance of the satellite from the Earth’s surface is smallest. The smallest distance of the satellite from the Earth’s surface is also called perigee of the orbit of the satellite.

3) Inclination: The angle between the plane of orbit of the satellite and plane of the equator of Earth is called inclination of the orbit.

TYPES OF ORBITS

1) Polar Orbits – A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth) on each revolution.

– These orbits have an inclination near 90 degrees. This allows the satellite to see virtually every part of the Earth as the Earth rotates underneath it. The important features of the satellites revolving in polar orbits are as follows:

• A satellite in a polar orbit will pass over the equator at a different longitude on each of its orbits.
• It takes approximately 90 minutes for the satellite to complete one orbit.

– These satellites have many uses like measuring ozone concentrations in the stratosphere or measuring temperatures in the atmosphere; earth mapping and observation; reconnaissance; study of weather etc.

2) Sun Synchronous Orbits – A satellite whose time period is such that it makes exactly an integral number of revolutions (usually 13, 14 or 15) around earth in 24 hours. After passing over a certain place on Earth, next day it will again pass over the same place at the same time of day.

– While Earth spins one rotation, relative to sun in 24 hours, the satellite makes an accurately integral number of revolutions. Thus, satellite will be able to look at that place and photograph it on consecutive days in identical illumination, Sun being in the same position relative to that place. Such an orbit is called a sun-synchronous orbit & the satellite moving in this orbit is called a sun-synchronous satellite. The important features of the satellites moving in the sun synchronous orbits are as follows:

• These orbits allow a satellite to pass over a section of the Earth at the same time of day. Since there are 365 days in a year and 360° in a circle, it means that the satellite has to shift its orbit by approximately 1° per day.
• These satellites orbit at an altitude between 700 to 800 km.

– These satellites are very important for military and remote sensing purposes.

3) Geosynchronous Orbits/ Geostationary Orbit – The satellites in these orbits circle the Earth at the same rate as the Earth spins. The orbit of such satellite is in the plane of equator, i.e. its inclination is 0o, at a height of about 36,000 km above the equator and keeps this distance constant.

– Thus, it is a circular orbit. Hence, relative to any location on earth, the position of the satellite is stationary. This orbit is called geo-stationary orbit. A satellite revolving in this orbit is called a geo-stationary satellite. The important features of the satellites moving in the geostationary orbits are as follows:

• Geosynchronous orbits allow the satellite to observe almost a full hemisphere of the Earth. These satellites are used to study large scale phenomenon such as hurricanes, or cyclones.
• These orbits are also used for communication satellites. The disadvantage of this type of orbit is that since these satellites are very far away, they have poor resolution. The other disadvantage is that these satellites have trouble monitoring activities near the poles.

4) Low Earth Orbit (LEO) – The Low Earth Orbit extends from 200 km. to 1200 km. It means that it is relatively low in altitude, although well above anything that a conventional aircraft can reach. However LEO is still very close to the Earth, especially when compared to other forms of satellite orbit including geostationary orbit. The important features of the Low Earth Orbit are as follows:

– Orbit times are much less than for many other forms of orbit.
– Less energy is expended placing the satellites in LEO than higher orbits.
– The lower orbit means the satellite and user are closer together and therefore path losses a less than for other orbits such as GEO.
– LEO satellites have shorter life spans than others
– Some speed reduction may be experienced as a result of friction from the low, but measurable levels of gasses, especially at lower altitudes.
– Radiation levels are lower than experienced at higher altitudes.

• A variety of different types of satellite use the LEO orbit levels. These include different types and applications including communications satellites, earth monitoring satellites etc.
• The International Space Station is in an LEO that varies between 320 km. (199 miles) and 400 km. (249 miles) above the Earth’s surface.

Space Debris in LEO – Apart from the general congestion experienced in Low Earth Orbit, the situation is made much worse by the general level of space debris that exists. There is a real and growing risk of collision and major damage – any collisions themselves are likely to create further space debris.

5) Medium Earth Orbits (MEO) – They are in between LEO and geostationary orbits & operate about 8,000-20,000 km. above the earth. They are placed in an elliptical orbit.

– The orbit is basically used for communication satellites.
– Examples include GPS and Global Communication and Orblink.

LAUNCH VEHICLES
1) ASLV:
• Augmented Satellite Launch Vehicle (ASLV) was developed to act as a low cost intermediate vehicle to demonstrate and validate critical technologies.
• With a lift off weight of 40 tonnes, the 23.8 m tall ASLV was configured as a 5 stage, all-solid propellant vehicle, with a mission of orbiting 150 kg class satellites into 400 km circular orbits.
• The strap-on stage consisted of 2 identical 1m diameter solid propellant motors, Under the ASLV programme 4 developmental flights were conducted.
• ASLV provided valuable inputs for further development.

2) PSLV
• The Polar Satellite Launch Vehicle, usually known as PSLV is the 1st operational launch vehicle of ISRO.
• PSLV is capable of launching 1600 kg satellites in 620 km. sun-synchronous polar orbit and 1050 kg. satellite in Geo-synchronous Transfer Orbit (GTO).
• In the standard configuration, it measures 44.4 m. tall, with a lift off weight of 295 tonnes.
• PSLV has 4 stages using solid and liquid propulsion systems alternately. The 1st stage is one of the largest solid propellant boosters in the world and carries 139 tonnes of propellant.
• A cluster of 6 strap-ons attached to the 1st stage motor, 4 of which are ignited on the ground and 2 are air-lit.
• The reliability rate of PSLV has been superb. With its variant configurations, PSLV has proved its multi-payload, multi-mission capability in a single launch and its Geosynchronous launch capability.

3) GSLV Mk I & II
• Geosynchronous Satellite Launch Vehicle (GSLV)-Mark I&II , is capable of placing INSAT-II class of satellites (2000 – 2,500 kg) into Geosynchronous Transfer Orbit (GTO). GSLV is a 3 stage vehicle GSLV is 49 m tall, with 4141 lift off weight.
• It has a maximum diameter of 3.4 m at the payload fairing. 1st stage comprises S125 solid booster with four liquid (L40) strap-ons. 2nd stage (GS2) is liquid engine and the 3rd stage (GS3) is a cryo stage. The vehicle develops a lift off thrust of 6573 km.

4) GSLV Mk III
• The GSLV-III or Geosynchronous Satellite Launch Vehicle Mark III is a launch vehicle currently under development by the Indian Space Research Organization.
• GSLV Mk III is conceived and designed to make ISRO fully self reliant in launching heavier communication satellites of INSAT-4 class, which weigh 4500 to 5000 kg.
• It would also enhance the capability of the country to be a competitive player in the multimillion dollar commercial launch market.
• The vehicle envisages multi-mission launch capability for GTO, LEO, Polar and intermediate circular orbits.

5) Reusable Launch Vehicle
• A reusable launch system (or reusable launch vehicle, RLV) is a launch system which is capable of launching a launch vehicle into space more than once. This contrasts with expendable launch systems, where each launch vehicle is launched once and then discarded.
• Reusable Launch Vehicle-Technology Demonstration (RLV-TD) Programme of ISRO is planned as a series of technology demonstration missions that have been considered as a first step towards realising a Two Stage To Orbit (TSTO) fully reusable vehicle.
• A Winged RLV-TD has been configured to act as a flying test bed to evaluate various technologies using air breathing propulsion. These technologies will be developed in phases through a series of experimental flights.
• Hypersonic experiment (HEX) flight, the first in the series of experimental flights, will be followed by the Landing experiment (LEX), Return flight experiment (REX) and Scramjet Propulsion experiment (SPEX).
• RLV-TD HEX1 is planned to demonstrate the hypersonic aerothermo dynamic characterisation of winged re-entry body, autonomous mission management to land at a specified location and characterisation of hot structures.
• Application of these technologies would bring down the launch cost by a factor of 10.

Scramjet Engine – TD
• The first experimental mission of ISRO’s Scramjet Engine towards the realisation of an Air Breathing Propulsion System was successfully conducted from Satish Dhawan Space Centre SHAR, Sriharikota.
• The Scramjet engine designed by ISRO uses Hydrogen as fuel and the Oxygen from the atmospheric air as the oxidiser. This test was the maiden short duration experimental test of ISRO’s Scramjet engine with a hypersonic flight at Mach 6. ISRO’s Advanced Technology Vehicle (ATV), which is an advanced sounding rocket, was the solid rocket booster used for the test of Scramjet engines at supersonic conditions.  ATV carrying Scramjet engines weighed 3277 kg at lift-off.

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