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geostationary and sun-synchronous

Orbital characteristics of Remote sensing satellite geostationary and sun-synchronous

 Orbits in Remote Sensing

  • Orbit = the path a satellite follows around the Earth.

  • The orbit determines what part of Earth the satellite can see, how often it revisits, and what applications it is good for.

  • Remote sensing satellites mainly use two standard orbits:

    • Geostationary Orbit (GEO)

    • Sun-Synchronous Orbit (SSO)

 Geostationary Satellites (GEO)

Characteristics

  • Altitude: ~35,786 km above the equator.

  • Period: 24 hours → same as Earth's rotation.

  • Orbit type: Circular, directly above the equator.

  • Appears "stationary" over one fixed point on Earth.

Concepts & Terminologies

  • Geosynchronous = orbit period matches Earth's rotation (24h).

  • Geostationary = special type of geosynchronous orbit directly above equator → looks fixed.

  • Continuous coverage: Can monitor the same area all the time.

Applications

  • Weather satellites (e.g., INSAT, GOES) → continuous monitoring of clouds, storms, cyclones.

  • Telecommunication & broadcasting → because the antenna can always point at the same satellite.

 Sun-Synchronous Satellites (SSO)

Characteristics

  • Altitude: ~600–900 km (Low Earth Orbit).

  • Period: ~90–100 minutes (around 14 orbits per day).

  • Orbit inclination: near-polar (~98°).

  • Passes the same spot at the same local solar time every day → ensures consistent sunlight conditions.

Concepts & Terminologies

  • Near-polar orbit: passes close to the poles → covers almost all Earth's surface.

  • Sun-synchronous = orbit shifts slightly every day so the satellite crosses each location at the same local solar time → ideal for comparing images over time.

  • Revisit cycle = how often the satellite passes over the same area (e.g., every 5–16 days depending on mission).

Applications

  • Earth observation & remote sensing (Landsat, Sentinel, IRS, Cartosat, ResourceSat).

  • Environmental monitoring: forests, agriculture, urban growth, glaciers.

  • Disaster management: floods, earthquakes, landslides.

GEO vs. SSO (Simplified Comparison)

FeatureGeostationary (GEO)Sun-Synchronous (SSO)
Altitude~36,000 km600–900 km
CoverageFixed area, ~⅓ of EarthGlobal (pole-to-pole)
Revisit timeContinuous over one regionSame spot daily at same solar time
Best forWeather, communicationEarth observation, mapping
ExamplesINSAT, GOES, MeteosatLandsat, Sentinel, IRS, Cartosat


  • Geostationary satellites stay fixed over one region → great for real-time monitoring (weather, communication).

  • Sun-synchronous satellites orbit pole-to-pole and give global coverage with consistent sunlight → great for mapping and scientific studies.


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