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Use of INSAT Satellites to analyse Fog

Facts for Prelims (FFP)


Source: TH

 Context: Large parts of North India, including Bihar, Uttar Pradesh, Uttarakhand, Haryana, Delhi, and Punjab, have been experiencing heavy fog since December 2023. The India Meteorological Department (IMD) utilizes satellite data, particularly from INSAT 3D and INSAT 3DR, to track and analyze the fog.


How Indian National Satellite (INSAT) System Help in Weather Analysis?

Key AspectsDescription
Advanced ImagingINSAT satellites like 3D and 3DR use RGB imagers for solar reflectance and brightness temperature analysis.
Strategic OrbitsGeostationary orbits of satellites like INSAT 3D and 3DR ensure continuous monitoring over India for real-time analysis.
Day and Night MonitoringEquipped with ‘day microphysics’ and ‘night microphysics,’ these satellites track weather changes around the clock.
Snow and Cloud DifferentiationThe satellites distinguish between snow and clouds based on reflectance in different spectral bands.
Enhanced PredictionsCombining day and night data facilitates tracking cyclone formation and predicting thunderstorms, improving early warnings.
Advanced RadiometersUpgraded radiometers in satellites like 3DR offer superior spatial resolution and functionality.
Atmospheric SoundersInstruments measure temperature, humidity, and water vapour, providing detailed atmospheric profiles for analysis.
Continual ImprovementEach new satellite in the INSAT series incorporates improved. The INSAT 3DS meteorological satellite, expected to launch in February 2024, will further enhance India’s weather monitoring capabilities.


How Satellites Analysis Color and Snow

Satellites, such as INSAT 3D, use RGB (Red, Green, Blue) imaging for colour determination based on solar reflectance and brightness temperature. This involves analyzing visible, shortwave infrared, and thermal infrared signals to represent green, red, and blue colours. The unique signature of snow, which reflects similarly to clouds in the visible spectrum but strongly absorbs shortwave infrared radiation, enables satellites to distinguish snow from clouds.


India has several weather satellites:

  1. Kalpana 1 (2002-2017): Geostationary orbit, equipped with early VHRR and data-relay transponder, deactivated in 2017 after 15 years.
  2. INSAT 3A (2003): Carried a three-channel VHRR for meteorological observations with different resolutions for visible, thermal infrared, and water vapour bands.
  3. INSAT 3D and 3DR: Geostationary orbits at 82 and 74 degrees east longitudes, featuring upgraded VHRRs for improved spatial resolution and functionality. They also carry atmospheric sounders for measuring temperature, humidity, and water vapour.
  4. Upcoming INSAT 3DS (Scheduled for February 2024): To be launched by the Indian Space Research Organisation using the GSLV Mk II launch vehicle. The “3DS” indicates it’s a subsequent iteration following the INSAT 3D and 3DR series.