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Satellites and Remote Sensing
4.1 Indian Satellite Series
Communication Satellites — INSAT/GSAT Series
- INSAT (Indian National Satellite System): India's multipurpose satellite series since 1983; handles direct-to-home TV, mobile satellite services, disaster warning, and meteorology
- GSAT series: Advanced communication satellites on GTO
- GSAT-11 (2018): India's most powerful communication satellite; capacity: 14 Gbps
- GSAT-30 (2020): Extended INSAT coverage
Earth Observation Satellites — IRS/RESOURCESAT/CARTOSAT
| Satellite | Year | Resolution | Application |
|---|---|---|---|
| IRS-1A | 1988 | 72.5 m | India's first IRS satellite |
| RESOURCESAT-2A | 2016 | 5.8 m (LISS-4) | Agriculture, land use, forest mapping |
| CARTOSAT-1 | 2005 | 2.5 m | Urban planning, terrain mapping |
| CARTOSAT-2 | 2007 | 0.8 m | Urban mapping |
| CARTOSAT-3 | 2019 | 0.25 m | Highest resolution India satellite; defence mapping |
| RISAT-1 | 2012 | SAR (1 m) | All-weather, day-night imaging (floods, agriculture) |
| RISAT-2BR1 | 2019 | SAR (0.35 m) | Enhanced all-weather surveillance |
Navigation Satellites — NavIC
- Constellation: 7 operational satellites (3 geostationary + 4 geosynchronous)
- Coverage: India + 1,500 km surrounding region
- Accuracy: < 20 m for standard users; < 10 m for encrypted military signal
- Applications: disaster management, fleet management, navigation, precise time dissemination, fishing vessel tracking
- India mandated NavIC chip in all smartphones sold in India from January 2023 (BIS notification)
Scientific Satellites
Astrosat (2015) is India's first dedicated multi-wavelength space observatory. It observes celestial objects simultaneously in UV, optical, and X-ray bands.
4.2 Remote Sensing Technology
Remote sensing means collecting information about Earth's surface or atmosphere using sensors carried on satellites or aircraft, without direct physical contact.
Types of Sensors
- Optical/Passive sensors: Detect reflected sunlight (LISS-4 on RESOURCESAT); cannot operate at night or through clouds
- SAR (Synthetic Aperture Radar)/Active sensors: Emit radar pulses and detect the reflection; advantage is all-weather, day-night imaging (RISAT series)
- Thermal infrared sensors: Detect emitted heat — map urban heat islands, forest fires, ocean surface temperature
- Hyperspectral sensors: Capture hundreds of spectral bands — detect specific minerals, crop stress, water quality
Applications in India
| Application | Satellite/System Used |
|---|---|
| Agricultural crop monitoring | RESOURCESAT-2A (Kharif/Rabi crop mapping) |
| Flood mapping and disaster relief | RISAT-1 (all-weather), CARTOSAT |
| Forest fire detection | MODIS (global), INSAT thermal data |
| Coastal zone management | IRS + OCEANSAT |
| Urban expansion mapping | CARTOSAT-3 (0.25 m) |
| Border surveillance | CARTOSAT-3, RISAT (used by Army) |
| Ocean applications | OCEANSAT-3 (2022) — fisheries, chlorophyll, SST |
| Groundwater assessment | IRS + LISS + microwave |
| MGNREGS work verification | BHUVAN (ISRO's geoportal) |
BHUVAN is ISRO's geospatial portal (launched 2009) — India's alternative to Google Earth. It provides satellite imagery, 3D terrain visualization, disaster monitoring, and integration with government scheme data.