UPSC Prelims Practice Questions — What remote-sensing reveals about plants, forests, and minerals from space

Q1. In the context of satellite remote sensing, the term 'spectral signature' of a surface material refers to which one of the following?

  • A. The characteristic pattern of reflectance and absorption exhibited by the material across different wavelengths of the electromagnetic spectrum
  • B. The smallest ground area, in metres, that a sensor can resolve as a single pixel
  • C. The repeat-cycle period after which a sun-synchronous satellite revisits the same point on Earth
  • D. The radiometric calibration coefficient applied to raw digital numbers from a sensor

Q2. The NISAR satellite, launched jointly by NASA and ISRO in July 2025, is notable as the world's first Earth observation satellite to carry which one of the following?

  • A. A dual-frequency synthetic aperture radar operating simultaneously in L-band and S-band
  • B. A hyperspectral imager covering more than 200 contiguous narrow spectral bands
  • C. A space-borne LiDAR dedicated to global forest-canopy height measurement
  • D. A geostationary multispectral scanner for continuous Indian Ocean coverage

Q3. From its sun-synchronous orbit, the NISAR mission (launched in July 2025) is designed to scan nearly all of Earth's land and ice surfaces how many times during every 12-day repeat cycle?

  • A. Once
  • B. Twice
  • C. Four times
  • D. Six times

Q4. The National Remote Sensing Centre (NRSC), which acquires and disseminates Indian Earth-observation satellite data and operates the Shadnagar ground station, functions under which one of the following?

  • A. Department of Space
  • B. Ministry of Earth Sciences
  • C. Department of Science and Technology
  • D. Ministry of Environment, Forest and Climate Change