Satellite OrbitsWritten by Gary Davis
Continued from page 1
In order to do this satellite has a very special orbit. Not only does it orbit earth, but plane of orbit changes as well. It has to do this because each day earth moves a bit through space around. After 3 months, earth has moved 90 degrees of its orbit around sun. If satellites orbit wouldn’t have moved with it, it would show up 6 hours later than planned. (Actually earth spins around its axis in approx. 23 hours, 56 minutes and 3 seconds and not in 24 hours. Because of earth’s orbit around sun, 1 day lasts 24 hours. A star day however is approx. 23 hours, 56 minutes and 3 seconds long.) However, there is no need to actively change plane of orbit. The earth is not a perfect sphere but is a little bit wider around equator. This is caused by spinning of earth. The gravitational difference this causes changes orbit of a satellite. When angle with equator is chosen correctly (approx. 8 degrees of a polar orbit), an orbit is a sun synchronous orbit. A very special type of sun synchronous orbit is called dawn-to-dusk orbit. This orbit is above earth where sun comes up or goes down. A satellite in this orbit never enters shadow of earth but always receives sunlight. Orbit Decay and Reentry The earth’s atmosphere doesn’t stop at a certain altitude but really fades out into space. The higher you get less thick it is until eventually there is no more atmosphere. Generally we say that atmosphere is about 100 km (62 miles) thick, but in reality it extends much further out into space. Satellites experience friction from atmosphere up to altitudes of 1000 km (620 miles). Due to friction, a satellite will loose speed and with that altitude will decrease until eventually satellite will fall out of orbit back to earth. Depending on altitude this happens sooner or later. A satellite at an altitude of 200 km (124 miles) will stay in orbit for just a couple of months. At 300 km (186 miles) a satellite can stay in orbit for a couple of years. Above 1000 km (620 miles) a satellite can stay in orbit for thousands of years. Letting Satellites fall back to earth and burn up in atmosphere is also a way of disposing of satellites.
Gary Davis is owner of Dish Network Satellite TV, has several years experience in the Satellite TV Industry and has written several articles on satellite TV.
| | The Ministry?s Sound AgendaWritten by Chris Meehan
Continued from page 1
The latest issue in what has been a well-received series is The Ministry?s: The Annual 2005 ? It features a tasty mix of year?s spiciest dance tunes, served up on two CDs. CD 1is a frisky mix of big numbers that have held sway throughout British club scene. These include Armand Van Helden?s My My My, Call On Me ?Eric Prydz ? Soul Central?s Strings of Life and Girls by The Prodigy. CD 2 has a harder edge to it, and diamonds in this package would have to be Judge Jules? remix of Michael Woods, Delirium?s Silence, JJ?s So Special and Kristine Blond?s Loveshy. The limited edition box set has a bonus DVD, with plenty of piquant vid footage, as an extra condiment. _=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_=_= This article was written by Chris Meehan who is features editor at www.Just-Jammin.com . You may use this article on your site as long as this resource box is included as is with a clickable link back to Just Jammin Copyright: PC Meehan 2005
Chris Meehan is the features editor at www.Just-Jammin.com. As well as a freelance writer on many subjects
|
