Orbital velocity project, Study Guides, Projects, Research of Physics

Download Orbital velocity project and more Study Guides, Projects, Research Physics in PDF only on Docsity!

GEOSTATIONARY

SATELLITES AND

ORBITAL VELOCITY

What is Gravitation?

Gravitation is a natural phenomenon by which all things with mass or energy, including planets, stars, galaxies , and even light, are attracted to (or gravitate toward) one another. On Earth, gravity gives weight to physical objects, and the Moon's gravity causes the tides of the oceans. The gravitational attraction of the original gaseous matter present in the Universe caused it to begin coalescing and forming stars and caused the stars to group together into galaxies, so gravity is responsible for many of the large-scale structures in the Universe. Gravity has an infinite range, although its effects become weaker as objects get farther away. gravitation is a natural phenomenon by which all things with mass or energy, including planets, stars, galaxies and even light, are attracted to (or gravitate toward) one another. On Earth, gravity gives weight to physical objects, and the Moon's gravity causes the tides of the oceans. The gravitational attraction of the original gaseous matter present in the Universe caused it to begin coalescing and forming stars and caused the stars to group together into galaxies, so gravity is responsible for many of the large-scale structures in the Universe. Gravity has an infinite range, although its effects become weaker as objects get farther away.

◦ (^) A single geostationary satellite is on a line of sight with about 40 percent of the earth's surface. Three such satellites, each separated by 120 degrees of longitude, can provide coverage of the entire planet, with the exception of small circular regions centered at the north and south geographic poles. A geostationary satellite can be accessed using a directional antenna, usually, a small dish, aimed at the spot in the sky where the satellite appears to hover. The principal advantage of this type of satellite is the fact that an earthbound directional antenna can be aimed and then left in position without further adjustment. Another advantage is the fact that because highly directional antennas can be used, interference from surface-based sources, and from other satellites, is minimized.

◦ (^) There are two other, less serious, problems with geostationary satellites. First, the exact position of a geostationary satellite, relative to the surface, varies slightly over the course of each 24-hour period because of gravitational interaction among the satellite, the earth, the sun, the moon, and the non-terrestrial planets. As observed from the surface, the satellite wanders within a rectangular region in the sky called the box. The box is small, but it limits the sharpness of the directional pattern, and therefore the power gain, that earth-based antennas can be designed to have. Second, there is a dramatic increase in background EM noise when the satellite comes near the sun as observed from a receiving station on the surface, because the sun is a powerful source of EM energy. This effect, known as solar fade, is a problem only within a few days of the equinoxes in late March and late September. Even then, episodes last for only a few minutes and take place only once a day.

What Factors Affect Orbital Velocity?

◦ (^) Orbital velocity is made possible by the curved surface of a planet, star, or other celestial body. An orbiting object tends to move in a straight line, whereas the body it is orbiting curves. As such the constant curvature of the orbited body prevents the orbiting object from falling all the way to the surface, provided that the orbiting object maintains the proper speed. ◦ (^) In space, it is easier to maintain a constant speed than it is on Earth, due to the principle of inertia. One of Sir Isaac Newton’s laws of inertia states that an object in motion tends to stay in motion unless acted on by an outside force. Within the earth’s atmosphere, a flying object encounters many air molecules, which cumulatively slow the speed of that object as it flies through the sky. As you journey beyond the earth’s atmosphere into higher altitudes, the air becomes more vacuous, with fewer molecules to counteract the forward velocity of an orbiting satellite.

What Is the Difference Between Orbital Velocity and

Escape Velocity?

◦ (^) It takes a certain level of velocity for an object to achieve orbit around a celestial body such as Earth. It takes even greater velocity to break free of such an orbit. When astrophysicists design rockets to travel to other planets—or out of the solar system entirely—they use the rotational velocity of the Earth to speed up the rockets and launch them out and beyond orbit. The speed required to break free of an orbit is known as escape velocity. ◦ (^) If a spaceship in orbit fires its engine long enough, it will eventually go fast enough to fly away into deep space, escaping the planet’s gravity. That escape velocity is simply the square root of 2, or 41% faster than orbital speed.