Satellites and Orbits

A satellite is any object that revolves around a planet or another larger body in space. Satellites can be:

• Natural – like the Moon orbiting Earth.
• Artificial – human-made objects launched into space for communication, weather monitoring, navigation, and research.

All satellites stay in their paths because of the balance between gravity and their forward motion.

A satellite stays in orbit because two effects balance each other:

• Gravity pulls the satellite toward Earth.
• Forward velocity pushes it sideways.

This combination results in a curved path around Earth. The satellite keeps “falling” toward Earth, but because it moves forward fast enough, the Earth curves away beneath it—so it never hits the ground.

Orbital velocity is the speed a satellite must have to remain in orbit. Near Earth’s surface, this value is approximately:

Satellites are placed in different orbits depending on their purpose. The most common orbits include:

Satellites have both kinetic energy (because they are moving) and gravitational potential energy (because they are at a height). The total mechanical energy of a satellite in a circular orbit is:

This negative energy signifies that the satellite is bound to Earth’s gravitational field.

Satellites are carried by rockets. The rocket propels the satellite upward and then horizontally to achieve the required orbital velocity. Once the satellite reaches the correct altitude and speed, it detaches and continues orbiting.

Satellites support modern life in countless ways:

• Communication and internet
• Navigation (GPS)
• Weather forecasting
• Military surveillance
• Scientific research and space observation

Next, we will explore a specific type of satellite: geostationary and polar satellites, and understand how their orbits differ.