Sun-Synchronous Orbit: Advantages and Disadvantages

This article explores the benefits and drawbacks of Sun-synchronous orbits.

What is a Sun-Synchronous Orbit?

Introduction: A Sun-synchronous orbit is a near-polar Earth orbit where the satellite passes over any given point on Earth at roughly the same local solar time. This is achieved by carefully selecting the altitude and inclination of the orbit.

Typically, this orbit lies at an altitude of 700 to 800 km above the Earth.

The orbital plane of a satellite in this orbit shifts approximately one degree per day, maintaining its relationship with the Sun. Satellites in Sun-synchronous orbits cover each area of the world at a consistent local time.

Benefits (Advantages) of Sun-Synchronous Orbit

Here are the key advantages of using a Sun-synchronous orbit:

• Consistent Lighting Conditions: The orbit is designed so that the angle between the orbital plane and the Sun remains relatively constant. This results in predictable and consistent lighting conditions for the satellite’s sensors, which is crucial for applications like Earth observation.
• Polar Monitoring: Unlike many other satellite orbits, Sun-synchronous orbits enable monitoring activities near the poles.
• Global Coverage: Sun-synchronous satellites regularly cover the entire globe, providing repetitive coverage on a periodic basis. A satellite passes over all places on Earth having the same latitude twice in each orbit at the same local solar time.
• Good Ground Resolution: The relatively low altitude of this orbit (compared to geostationary orbits) allows for good ground resolution for imaging and other remote sensing applications.
• Easy Active Measurements: This orbit facilitates active measurements using radar or lidar (light detection and ranging) technologies.

Drawbacks (Disadvantages) of Sun-Synchronous Orbit

Despite the advantages, Sun-synchronous orbits have some limitations:

• No Continuous Spot Viewing: Satellites in this orbit cannot continuously view a specific spot on the Earth’s surface. Geosynchronous satellites are better suited for this purpose.
• Limited Weather Forecasting Use: While useful, data from polar-orbiting satellites (which include Sun-synchronous) is sometimes less directly applicable for real-time weather forecasting than data from geosynchronous satellites.
• Less Frequent Observation of a Specific Spot: Sun-synchronous satellites pass over polar regions twice a day. Geostationary satellites, with an orbital period of approximately 24 hours, can view a particular spot on the Earth’s surface continuously.

Conclusion

Understanding the advantages and disadvantages of Sun-synchronous orbits is crucial for selecting the right orbit for a specific satellite mission. Its unique characteristics make it ideal for Earth observation, environmental monitoring, and other applications requiring consistent lighting and global coverage.