UPSC Prelims Practice Questions — Nightlights are not just getting brighter everywhere

Q1. In nighttime-lights remote sensing, the 'Day/Night Band (DNB)' of the VIIRS instrument — the basis of NASA's Black Marble product — is best described as:

  • A. A low-light panchromatic sensor with multiple gain stages that detects faint visible-to-near-infrared radiance at night
  • B. A thermal-infrared channel that maps land-surface temperature after sunset
  • C. A microwave radar band that penetrates cloud cover to image built-up area at night
  • D. A hyperspectral band that measures atmospheric aerosol scattering of moonlight

Q2. With reference to the VIIRS sensor that generates NASA's Black Marble nighttime-lights imagery, consider the following as satellite platforms that carry a VIIRS instrument. Which of the above is/are NOT correctly identified?

  1. Suomi-NPP
  2. NOAA-20
  3. NOAA-21
  4. Landsat-8
  • A. 1 only
  • B. 2 and 3
  • C. 4 only
  • D. 1 and 4

Q3. In the history of nighttime-lights remote sensing, 'DMSP-OLS' — the principal source of nightlight imagery before VIIRS — refers to:

  • A. The Operational Linescan System flown on the U.S. Defense Meteorological Satellite Program
  • B. An ocean-colour scanner flown on India's early ocean-monitoring satellites
  • C. A European Space Agency radar altimeter for measuring sea-surface height
  • D. A geostationary lightning mapper operated by NOAA

Q4. Nighttime-light composites from the DMSP-OLS sensor were archived and distributed as a long-term economic-proxy dataset chiefly by which agency?

  • A. The U.S. National Oceanic and Atmospheric Administration (NOAA)
  • B. NASA's Jet Propulsion Laboratory
  • C. The U.S. Geological Survey's EROS Center
  • D. The European Space Agency

Q5. With reference to the 2026 Nature study on global nighttime lights, consider the following statements. Which of the statements given above is NOT correct?

  1. It analysed VIIRS Day/Night Band imagery for the period 2014–2022.
  2. Global nighttime radiance rose by about 34% over the study period.
  3. Localized dimming offset roughly 18% of the global radiance gain.
  4. It concluded that every inhabited region brightened uniformly, with no area dimming.
  • A. 1 and 2
  • B. 3 only
  • C. 4 only
  • D. 2 and 3

Q6. The 2026 Nature study that documented simultaneous global brightening and dimming of nighttime lights, using the VZA-COLD algorithm, was led by researchers at which institution (in collaboration with NASA)?

  • A. University of Connecticut
  • B. University of Maryland
  • C. Massachusetts Institute of Technology
  • D. California Institute of Technology

Q7. With reference to the Saubhagya scheme, whose electrification drive shows up as rising nighttime radiance across northern India, consider the following statements. Which of the statements given above is NOT correct?

  1. It provided last-mile electricity connections to un-electrified rural households.
  2. It provided solar photovoltaic standalone systems to remote households where grid extension was not feasible.
  3. It covered economically poor un-electrified households in urban areas.
  4. It guaranteed free monthly units of electricity and a permanent waiver of tariffs for all beneficiary households.
  • A. 1 and 2
  • B. 3 only
  • C. 4 only
  • D. 2 and 4

Q8. 'Saubhagya', the scheme whose universal household-electrification push is visible as surging nighttime radiance in states such as Uttar Pradesh and Bihar, is the popular name of which scheme?

  • A. Pradhan Mantri Sahaj Bijli Har Ghar Yojana
  • B. Deen Dayal Upadhyaya Gram Jyoti Yojana
  • C. Pradhan Mantri Ujjwala Yojana
  • D. Pradhan Mantri Gram Sadak Yojana

Q9. The foundational econometric study establishing a measurable elasticity between nighttime-light intensity and GDP growth — the basis for later use of nightlights to estimate economic activity — was published by Henderson, Storeygard and Weil in which year?

  • A. 2012
  • B. 1998
  • C. 2005
  • D. 2019

Q10. With reference to regions and causes of localized dimming identified in the 2026 nighttime-lights study, consider the following. Which of the above is/are NOT correctly identified?

  1. Ukraine — sustained dimming following the 2022 Russian invasion
  2. France — dimming driven by LED retrofits and energy conservation
  3. Permian Basin of the United States — dimming caused by a collapse of oil and gas activity
  4. Syria and Yemen — dimming due to prolonged armed conflict
  • A. 1 and 2
  • B. 3 only
  • C. 4 only
  • D. 2 and 3

Q11. According to the World Atlas of artificial night sky brightness, for approximately what share of the world's population is the Milky Way no longer visible in the night sky?

  • A. About one-third
  • B. About one-tenth
  • C. About two-thirds
  • D. About nine-tenths

Q12. With reference to Earth-observation missions used for land and nighttime imaging, consider the following statements. Which of the statements given above is/are correctly identified?

  1. Bhaskara-1 and Bhaskara-2 were India's early experimental remote-sensing satellites carrying optical and microwave payloads.
  2. Cartosat-1 was the first Indian remote-sensing satellite capable of providing in-orbit stereo images.
  3. Resourcesat-2 was launched as a follow-on mission to Resourcesat-1.
  4. The VIIRS Day/Night Band used for Black Marble nighttime lights is carried aboard ISRO's Oceansat series.
  • A. 1, 2 and 3
  • B. 1 and 4
  • C. 2, 3 and 4
  • D. 1, 2, 3 and 4