5.10.1. Geo-synchronous Satellites

Geo-synchronous or Geo-stationary satellites move in an orbit so that it covers one revolution in the same time as the Earth rotates once about its polar axis. The satellites revolve in the same direction as that of the Earth (west to east) at an angular velocity equal to the Earth’s rotation rate.

Geo-synchronous satellites have a special orbit that matches the rotation speed of the Earth. This means that as the Earth spins on its axis, the satellite makes one complete revolution around the Earth at the same rate. This synchronization allows the satellite to appear to stay in the same spot in the sky relative to a specific point on Earth all the time.

Think of a geo-synchronous satellite like a carousel horse that moves along with a merry-go-round. If the horse were to match the speed of the ride perfectly, it would always be in the same position relative to someone standing on the ground watching it, just like how the satellite stays fixed over one specific spot on Earth.

To achieve this orbital period, geo-synchronous orbits are generally at high altitude of 36,000 km above the equator, making an inclination of 0° from the equatorial plane. Thus from any point on the equator, the satellite moving in such orbit appears to be stationary.

The altitude of geo-synchronous satellites is about 36,000 kilometers above the Earth's equator. They are positioned directly above the equator and do not tilt, meaning they move in a circle around the Earth without changing their elevation or angle relative to the surface. This positioning is crucial for them to maintain a constant view of the same area on Earth.

Imagine a spotlight that must shine on a specific stage at a concert. If you have to keep the spotlight fixed on one spot while the performers move, you need to find a position directly above the center of the stage and keep the light steady. Similarly, geo-synchronous satellites need to hover over a specific point to provide consistent coverage.

The INSAT series of satellites launched by Indian Space Research Organization, Department of Space, Government of India, is an example of these satellites.

One of the most notable examples of geo-synchronous satellites is the INSAT series from India's space agency. These satellites are used for various purposes such as communication, broadcasting television, and weather monitoring. Their ability to provide a constant view of specific regions makes them invaluable for services that require real-time data and updates.

Think of how security cameras work in stores. Some cameras stay pointed at a particular section (like the entrance) all the time. Similarly, geo-synchronous satellites continuously focus on specific areas to monitor weather conditions or send TV signals back to us, ensuring that we always have updated information.

The signals from these satellites are used for communication and television broadcast purposes. Since the images from these satellites cover a large area, the spatial resolution of such images is poor, and thus can’t be used for detailed natural resource mapping.

While geo-synchronous satellites are essential for communication and meteorological observations, one drawback is their spatial resolution. Because they are positioned far from the Earth, the images they capture cover a wide area but lack detailed clarity. This makes them less suitable for tasks that require high-resolution imaging, like detailed mapping of resources or features on the Earth's surface.

Picture taking a photo of a large crowd from a high pole. You can see everyone, but the details of individual faces are blurry. The same goes for geo-synchronous satellites; they can capture broad areas effectively, but fine details get lost, making it hard to analyze specific local features accurately.

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