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19 Jul 2026SCIENCE & TECHNOLOGY3 questions

Watching the Ocean From 700 km: Oceansat-3A and the Satellites That Find Fish

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Article summary

The Director of the National Remote Sensing Centre has indicated that Oceansat-3A, designated EOS-10, is likely to be launched by the end of the year, alongside the inauguration of a coastal observation research laboratory at Andhra University's Centre for Studies on Bay of Bengal. Oceansat-3A is the fourth satellite in ISRO's Oceansat series and carries four instruments: an Ocean Colour Monitor, a Scatterometer, a Sea Surface Temperature Monitor, and a Millimeter-wave Atmospheric Temperature and Humidity Sounder. Operating in tandem with Oceansat-3, also designated EOS-06, it is intended to provide daily coverage supporting identification of potential fishing zones, measurement of phytoplankton and chlorophyll concentration, coastal zone management, ocean dynamics, numerical weather prediction and cyclone monitoring. The pairing of two satellites is what converts periodic observation into operational forecasting.

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recallTests whether you read the article and retained key facts.
1Q
applicationTests whether you can apply the concept to a new scenario.
1Q
analysisTests whether you can reason across multiple related facts.
1Q

Sample questions — answers revealed after test

SCIENCE & TECHNOLOGYRecallEasy

Q1. On what physical principle does a satellite-derived Potential Fishing Zone advisory rest?

AThe satellite detects fish shoals directly by their acoustic signature.
BRadar altimetry measures sea surface height, from which the location of fish aggregations is computed.
CThermal imaging detects the body heat of fish schools near the surface.
DAn Ocean Colour Monitor derives chlorophyll concentration from the spectral reflectance of the sea surface, and fish aggregate where primary productivity is high.
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SCIENCE & TECHNOLOGYApplicationMedium

Q2. During a cyclone, dense cloud covers the storm system. Which of the satellite's instruments remains usable, and why?

AThe Ocean Colour Monitor, because chlorophyll fluorescence penetrates cloud.
BThe Scatterometer, because it is an active instrument transmitting its own microwave pulses, which pass through cloud and function equally at night.
CNone, since all orbital remote sensing requires a clear line of sight in visible wavelengths.
DThe Sea Surface Temperature Monitor, because thermal infrared is unaffected by water droplets in the atmosphere.
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SCIENCE & TECHNOLOGYAnalysisHard

Q3. Consider the following statements regarding satellite ocean observation: 1. Values such as chlorophyll concentration and sea surface temperature are inferred from radiance measurements and require calibration against in-situ observations. 2. Coastal waters present different optical conditions from the open ocean because of sediment load and river discharge, so regional validation is necessary. 3. Because the measurements are made by instruments of known specification, satellite-derived values are direct readings requiring no ground validation. Which of the statements given above are correct?

A1 only
B1 and 2 only
C2 and 3 only
D1, 2 and 3
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