Basics of Satellites: Satellites are objects that orbit around larger bodies in space. They are primarily used for communication, navigation, Earth observation, weather monitoring, scientific research, and more. Satellites can be categorized based on their orbits, functions, and sizes. They are launched into space using rockets and placed into specific orbits, depending on their intended purpose 1. Geostationary Earth Orbit (GEO) Satellites: GEO satellites orbit the Earth at an altitude of approximately 35,786 kilometers (22,236 miles) above the equator. They have an orbital period that matches the Earth's rotation, allowing them to remain stationary relative to a fixed point on the Earth's surface. GEO satellites are commonly used for communication, broadcasting, and weather monitoring because they provide continuous coverage of a specific region. 2. Low Earth Orbit (LEO) Satellites: LEO satellites orbit the Earth at altitudes ranging from about 160 kilometers (100 miles) to 2,000 kilometers (1,200 miles) above the Earth's surface. They complete an orbit around the Earth in a relatively short amount of time, typically ranging from 90 minutes to 2 hours. LEO satellites are used for various purposes, including Earth observation, remote sensing, satellite imaging, scientific research, and satellite constellations for global communications. 3. Medium Earth Orbit (MEO) Satellites: MEO satellites orbit the Earth at altitudes ranging from about 2,000 kilometers (1,200 miles) to 35,786 kilometers (22,236 miles) above the Earth's surface. They have orbital periods longer than LEO satellites but shorter than GEO satellites. MEO satellites are often used for navigation systems, such as the Global Navigation Satellite Systems (GNSS) like GPS (Global Positioning System), GLONASS (Global Navigation Satellite System), and Galileo. 4. Molniya Orbit Satellites: Molniya orbit is a specific type of highly elliptical orbit with a high inclination angle. Satellites in Molniya orbits have a long dwell time over high latitudes, making them suitable for communication and observation services in polar regions. These satellites are used for applications like communication in northern latitudes, remote sensing, and reconnaissance. 5. High Altitude Platform Stations (HAPs): HAPs are not traditional satellites but rather platforms stationed at high altitudes in the Earth's atmosphere, typically in the stratosphere. They are used to provide communication and surveillance services over a specific area. HAPs can be equipped with telecommunications equipment, antennas, and other technologies to relay signals between ground stations or act as relays for satellite communication systems. capacity allocation in satellite communications are Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA).