20 Topics.
0 of 10 Concepts Done
What to Study: Be clear about what remote sensing is and why it is done without touching the object. Remember the definition in terms of electromagnetic energy. Understand the steps from the energy source, to its interaction with the surface, to the sensor, and then to the processing of data.
What to Study: Which parts of the spectrum do satellites use (visible, infrared, thermal, microwave)? Understand what a spectral signature is and what an atmospheric window is. Why does healthy vegetation look bright in near-infrared light, and how does this lead to vegetation indices such as NDVI?
What to Study: Three platforms carry sensors: satellites, aircraft and drones. Which one gives wide, repeated coverage, and which gives fine detail over a small area? Understand why the choice depends on the task.
What to Study: How does a passive sensor get its energy, and how does an active sensor? Remember examples of each type. Can a passive sensor work at night, and which kinds can? Why can an optical camera not work at night? Do thermal sensors record reflected or emitted energy?
What to Study: For each family, what is measured: reflected light, emitted heat or microwaves? Which of them can see through cloud or in darkness, and why? Understand how this links to synthetic aperture radar and to thermal missions such as TRISHNA.
What to Study: Be clear about the four kinds of resolution and what each one measures, with an everyday example. Understand revisit time as temporal resolution. Why would a satellite that stays over one region improve temporal resolution?
What to Study: How do multispectral and hyperspectral sensors differ in the number and width of bands they use? Understand what hyperspectral imaging can reveal (minerals, crop stress, hidden objects). Remember HySIS. Was a hyperspectral satellite lost in a launch failure in January 2026, and which one?
Asked in UPSC PrelimsUPSC 2015UPSC 2019
What to Study: Uses in agriculture include crop identification, forecasting, damage assessment, soil and moisture mapping. Uses in natural resources include land use, wetlands and wildlife habitat. Also be clear about groundwater and mineral studies. Are Indian Remote Sensing (IRS) satellites used for telecommunication or traffic studies?
What to Study: Remember the hazards tracked from space: cyclones, earthquakes, erosion and floods. Understand how satellite data helps with early warning, with mapping damage afterwards, and with planning relief.
Asked in UPSC PrelimsUPSC 2010UPSC 2019
What to Study: Know the uses for weather and rainfall, ocean currents, temperature and sea ice, and for the environment (greenhouse-gas sources, canopy chlorophyll, ecosystem health). Why are aircraft sensors used along with satellites to find emission hotspots?