Remote Sensing Platforms & Satellite Orbits

Explanation

Orbital mechanics determine the coverage and lighting conditions of satellite imagery. Geostationary satellites orbit at 35,786 km, providing continuous high-temporal monitoring of an entire hemisphere, essential for tracking cyclones and cloud movements. Earth resource satellites (Landsat, Sentinel) operate in Sun-Synchronous Polar Orbits at 600-800 km altitude. Because they cross the equator at the exact same local solar time (e.g., 10:30 AM local time), solar illumination angles remain nearly constant across sequential seasons, minimizing shadow variations during change detection analysis.

Key points

• Geostationary Orbits (GEO): Positioned at ~35,786 km altitude directly above the Equator; orbital period matches Earth's rotation (24 hours); remains stationary over one spot (weather satellites: GOES, INSAT, Himawari).
• Sun-Synchronous Polar Orbits (SSO): Low Earth Orbit (LEO, 600-800 km altitude); inclined steeply near poles (~98 degrees); crosses the equator at the identical local solar time on every pass.
• Swath Width: Ground track width imaged by the sensor during a single orbital pass.
• Nadir: The point on the Earth's surface directly vertically beneath the satellite platform.

Example

Code examples

/*
Satellite Orbit Characteristics:
Parameter          | Geostationary Orbit (GEO)     | Sun-Synchronous Polar (SSO)
Altitude           | ~35,786 km                    | ~600 - 800 km
Inclination        | 0° (Equatorial plane)         | ~98° (Retrograde polar)
Orbital Period     | 24 hours                      | 90 - 100 minutes
Revisit Frequency  | Continuous (every 10-15 mins) | Days to weeks (e.g. 5-16 days)
Primary Use Case   | Weather forecasting, comms    | Earth resource mapping, land cover
*/

Exam questions

• [8 Marks] Compare Geostationary orbits and Sun-Synchronous Polar orbits with respect to altitude, inclination, revisit time, and applications.
• [6 Marks] Describe the characteristics, advantages, and limitations of Drone/UAV platforms compared to satellite remote sensing.