4) Why must a geostationary satelite be above the equator?
The plane of every orbit must pass through the center of the earth, because the gravity force acts from there.
You can have 24-hour orbits that are not coplanar with the equatorial plane, but the satellite would drift back and forth across the equatorial plane. From a point on the earth, the satellite would appear to go from north to south and back once a day.
A geostationary orbit requires the satellite to stay at the same place in the sky. This can only happen if the satellite is always above the equator.
There is a clear distinction between a geosynchronous orbit and a geostationary orbit. The early recognition of a geostationary orbit was made by the Russian Konstantin Tsiolkovsky early this century. Others referred to the unique orbit in writings about space travel, space stations, and communications. It was probably Arthur C. Clarke who was given the major credit for the use of this orbit for the purpose of worldwide communications.
The geostationary orbit is one where a spacecraft or satellite appears to hover over a fixed point on the Earth's surface. There is only one geostationary orbit in contrast to there being many geosynchronous orbits. What is the difference you ask? A geosycnchronous orbit is one with a period equal to the earth's rotational period, which, contrary to popular belief, is 23hr-56min-4.09sec., not 24 hours. Thus, the required altltude providing this period is ~22,238.64 miles, or ~35,787.875 kilometers. An orbit with this period and altitude can exist at any inclination to the equator but clearly, a satellite in any such orbit with an inclination to the equator, cannot remain over a fixed point on the Earth's surface. On the other hand, a satellite in an orbit in the plane of the earth's equator and with the required altitude and period, does remain fixed over a point on the equator. This equatorial geosynchronous orbit is what is referred to as a geostationary orbit. The orbital velocity of satellites in this orbit is ~10,088.25 feet per second or ~6,877 MPH. The point on the orbit where the circular velocity of the launching rocket reaches 10,088.25 fps, and shuts down, is the point where the separated satellite will remain. The point on the Earth's surface immediately below the satellite is moving with a velocity of 1525.85 ft./sec.
A geostationary satellite must be positioned above the equator because it orbits the Earth at the same rotational speed as the planet itself. This allows the satellite to appear stationary with respect to an observer on the ground.
To understand why a geostationary satellite needs to be above the equator, let's consider the motion of satellites. Satellites are essentially objects in space that orbit around a larger celestial body, such as Earth. The motion of satellites is determined by the gravitational pull of the celestial body they are orbiting.
When a satellite is launched into space, its initial speed must be carefully calculated based on its desired orbit. To achieve a geostationary orbit, the satellite must be placed at a specific distance from Earth, known as the geostationary orbit height.
The geostationary orbit is located about 35,786 kilometers (22,236 miles) above the Earth's equator. This is because the Earth completes one full rotation in approximately 24 hours. Therefore, to stay synchronized with the Earth's rotation, a geostationary satellite must have an orbital period of 24 hours as well.
If a satellite is placed in an orbit that is too close to Earth, it will move faster than the Earth's rotation. This means that from the perspective of an observer on the ground, the satellite would appear to be moving across the sky. On the other hand, if the satellite is placed in an orbit that is too far from Earth, it will move slower than the Earth's rotation. As a result, it will also appear to drift across the sky.
By placing the satellite above the equator, the satellite's orbital path aligns with the Earth's rotation. This allows the satellite to remain above the same spot on Earth's surface, providing continuous coverage for communication, weather monitoring, and other applications.
In summary, a geostationary satellite must be positioned above the equator to match the rotational speed of Earth, allowing it to remain fixed in a specific position relative to an observer on the ground.