A satellite is a moon, planet or machine that orbits a planet or star. For example, Earth is a satellite because it orbits the sun. Likewise, the moon is a satellite because it orbits Earth. Usually, the word “satellite” refers to a machine that is launched into space and moves around Earth or another body in space.
Earth and the moon are examples of natural satellites. Thousands of artificial, or man-made, satellites orbit Earth.
A. Astronomical Satellites
• These satellites are used for the observation of distant stars and other objects in space. India’s envisioned ASTROSAT is an Astronomical satellite.
• The most famous astronomical satellite is the Hubble Telescope. Although now reaching the end of its life it has enabled scientists to see many things that would otherwise not have been possible.
Astronomy Satellites have many Different Applications:
• They can be used to make star maps.
• They can be used to study mysterious phenomena such as Black holes and Quasars.
• They can be used to take pictures of the planets in the solar system.
• They can be used to make maps of different planetary surfaces.
B. Communications Satellites
• These satellites possibly form the greatest number of satellites that are in orbit. They are used for communicating over large distances. INSAT and GSAT of India comes under this category.
• The Indian National Satellite (INSAT) systems which are placed in Geo-stationary orbits are one of the largest domestic communication satellite systems in Asia-Pacific region.
• The height of the satellite above the Earth enables the satellites to communicate over vast distances, and thereby overcoming the curvature of the Earth’s surface.
Even within the communications field there are a number of sub-categories.
• Some satellites are used for point to point telecommunications links, others are used for mobile communications, and there are those used for direct broadcast. There are even some satellites used for mobile phone style communications.
C. Earth Observation Satellites
• These satellites are used for observing the earth’s surface and as a result they are often termed geographical satellites. India’s IRS and RESOURCESAT are part of this.
• The data is used for several applications covering agriculture, water resources, urban development, mineral prospecting, environment, forestry, drought and flood forecasting, ocean resources and disaster management.
• Using these satellites it is possible to see many features that are not obvious from the earth’s surface, or even at the altitudes at which aircraft fly.
• Using these earth observation satellites many geographical features have become obvious and they have even been used in mineral search and exploitation.
D. Navigation Satellites
• In recent years, satellites have been used for accurate navigation. The 1st system known as GPS (Global Positioning System) was set up by the USA and was primarily intended for use as a highly accurate military system. Since then, it has been adopted by a huge number of commercial and private users including India.
• India launched its own navigation satellite in the name of IRNSS-Indian Regional Navigation Satellite System.
E. Reconnaissance Satellites:
• These satellites are able to see objects on the ground and are accordingly used for military purposes. As such their performance and operation is kept secret and not publicized. DRONES are part of reconnaissance system.
F. Weather Satellites
• As the name implies these satellites are used to monitor the weather. They have helped considerably in the forecasting of the weather and have helped provide a much better understanding not only of the underlying phenomena, but also in enabling predictions to be made.
• India’s Kalpana-1 and INSAT-3A are part of this.
G. Student Satellites
• ISRO has influenced educational institutions by its activities like making satellites for communication, remote sensing and astronomy. The launch of Chandrayaan-1 increased the interest of universities and institutions towards making experimental student satellites. Capable Universities and institution can venture into space technology on orbit with guidance and support from ISRO in following ways:
• Every satellite carries a payload that performs the intended function to achieve the mission goal and the main bus that supports the payload function. The Development of payloads may comprise of detectors, electronics and associated algorithms, which can be an experimental piggy back payload on the ISRO’s on-going (Small or operational) satellite projects.
• Example- ANUSAT, STUDSAT, YOUTHSAT, Jugnu, SRMsat.
The Indian National Satellite (INSAT) system is one of the largest domestic communication satellite systems in Asia-Pacific region with nine operational communication satellites placed in Geo-stationary orbit. Established in 1983 with commissioning of INSAT-1B, it initiated a major revolution in India’s communications sector and sustained the same later. GSAT-18 joins the constellation of INSAT System consisting 14 operational satellites, namely – INSAT-3A, 3C, 4A, 4B, 4CR, 3DR and GSAT-6, 7, 8, 10, 12, 14, 15 and 16.
The INSAT system with more than 200 transponders in the C, Extended C and Ku-bands provides services to telecommunications, television broadcasting, satellite newsgathering, societal applications, weather forecasting, disaster warning and Search and Rescue operations.
a) EDUSAT Programme: EDUSAT, launched by Geosynchronous Satellite Launch Vehicle (GSLV-F01) in September 2004, is India’s first thematic satellite dedicated exclusively for educational services. The satellite is specially configured to relay through audio-visual medium, employing multi-media multi-centric system, to create interactive classrooms.
b) Educational TV Services: INSAT is being used to provide Educational TV (ETV) service for primary school children
c) Telemedicine Programme: ISRO’s telemedicine pilot project was started in the year 2001 with the aim of introducing the telemedicine facility to the grass root level population as a part of proof of concept technology demonstration. The telemedicine facility connects the remote District Hospitals/Health Centres with Super Specialty Hospitals in cities, through the INSAT Satellites for providing expert consultation to the needy and underserved population.
d) Television: INSAT has been a major catalyst for the expansion of television coverage in India. Satellite television now covers 100% area and 100% population. The terrestrial coverage is over 65 percent of the Indian land mass and over 90 percent of the population. All of the Satellite TV channels are digitalized.
e) Satellite Aided Search and Rescue: India is a member of the international COSPAS-SARSAT programme for providing distress alert and position location service through LEOSAR (Low Earth Orbit Search And Rescue) satellite system. Under this programme, India has established two Local User Terminals (LUTs), one at Lucknow and the other at Bangalore. The Indian Mission Control Centre (INMCC), is located at ISTRAC, Bangalore.
Indian LUTs provide coverage to a large part of Indian Ocean region rendering distress alert services to Bangladesh, Bhutan, Maldives, Nepal, Seychelles, Sri Lanka and Tanzania. The operations of INMCC/LUT are funded by the participating agencies, namely, Coast Guard, Airports Authority of India (AAI) and Director General of Shipping and Services.
f) Disaster management: The Disaster Management Support (DMS) Programme of ISRO, provides timely support and services from aero-space systems, both imaging and communications, towards efficient management of disasters in the country. The DMS programme addresses disasters such as flood, cyclone, drought, forest fire, landslide and Earthquake. These include creation of digital data base for facilitating hazard zonation, damage assessment, etc., monitoring of major natural disasters using satellite and aerial data; development of appropriate techniques and tools for decision support, establishing satellite based reliable communication network, deployment of emergency communication equipments and R&D towards early warning of disasters.
Starting with IRS-1A in 1988, ISRO has launched many operational remote sensing satellites. Today, India has one of the largest constellations of remote sensing satellites in operation. Currently, *thirteen* operational satellites are in Sun-synchronous orbit – RESOURCESAT-1, 2, 2A CARTOSAT-1, 2, 2A, 2B, RISAT-1 and 2, OCEANSAT-2, Megha-Tropiques, SARAL and SCATSAT-1, and *four* in Geostationary orbit- INSAT-3D, Kalpana & INSAT 3A, INSAT -3DR. Varieties of instruments have been flown onboard these satellites to provide necessary data in a diversified spatial, spectral and temporal resolutions to cater to different user requirements in the country and for global usage. The data from these satellites are used for several applications covering agriculture, water resources, urban planning, rural development, mineral prospecting, environment, forestry, ocean resources and disaster management.
List of Earth Observation Satellites
Applications of Remote Sensing Satellite
1. Agriculture & Soil
• Crop production forecast
• Saline/sodic soils mapping
• Agro-Met services& disaster surveillance (pest, floods, drought)
• Horticulture development
2. Bio Resources and Environment
• Forest cover and type mapping
• Wetland inventory & conservation plans
• Bio diversity characterization
• Desertification status mapping
• Coastal, mangroves, Coral Related
• Snow and glacier studies
• Large scale mapping
• Satellite based topo-map updation
• Digital Elevation Model (Carto-DEM)
• Cadastral level mapping
4. Geology and Mineral Resources
• Landslide hazard zonation
• Mineral /oil exploration, mining areas
• Seiesmo-tectonic studies
• Engineering and geo-environmental studies
5. Ocean and Meteorology
• Ocean primary productivity
• Ocean status forecast
• Storm surge modelling
• Regional weather prediction
• Tropical cyclone and mesoscale studies
• Extended range monsoon prediction
6. Rural Development
• National Drinking Water mission
• Wasteland mapping/updation
• watershed development and monitoring
• Land records modernization plan
7. Urban Development
• Urban sprawl mapping of major cities
• Master / structure plans
• Comprehensive development plans of selected cities / towns
• Base map generation for towns
• National urban information system
8. Water Resources
• Irrigation infrastructure assessment
• Water resource information system
• Snow melt run-off estimation
• Reservoir capacity evaluation
• Site selection for hydro-power
9. Natural Resources Census
• Periodic inventory of natural resources under NR Census programme
• Land use/land cover, soil, geomorphology, wetland, land degradation, snow and glacier, vegetation
10. Disaster Management Support
• Operationally addressing various natural disasters like floods, cyclone, drought, landslide, earthquake and forest fire
• Research and development on early warning systems and decision support tools
11. Climate Change Studies
• Mapping the indications, monitoring the agents and modelling the impact
• Characterization of climate variables
• Methane emission and Timberline study