EARTH’S SATELLITES

By Heba Jaleel and Ria

Biju

CONTENTS• What are satellites• Natural satellites• Earth’s moon• Application of the Moon• Artificial satellites• Types of artificial satellites• Satellite missions• Satellite orbits• Low earth orbit• Medium earth orbit• Geostationary earth orbit• Applications of artificial satellites

WHAT ARE SATELLITES ?

A satellite is a small body revolving around a plane.A satellite is held by the gravitational force of the planet and revolves around it.The orbit of the satellite can be predicted mathematically.The word satellite originated from the Latin word “satellit”-meaning an attendant, one who is constantly moving around the earth.

NATURAL SATELLITES A natural satellite is a celestial body that orbits another body. There are 173 known natural satellites orbiting the planets in in the solar system. Earth has one large natural satellite, known as the Moon.

EARTH’S MOON The Moon, whose formal name is La Luna, is the fifth largest moon in the world. The Moon orbits the earth once every 27.3days. This time period is called the orbital period or sidereal period. The moon is the only celestial body other than the earth on which humans have set foot. The time from one full moon to the next is 29.5days.

APPLICATIONS OF THE MOON

For most of our history, we were hunting or fishing or doing agriculture and organized our lives by using the Moon. That’s why most of our calendars are based on the Moon. Studying the Moon help us determine the distances in the solar system and the size of the celestial objects. The sight of many mammals is sensitive to moonlight. The Moon affects the liquid envelope of the Earth, and the oceanic tides in particular.

ARTIFICIAL SATELLITESo Artificial satellites is a manufactured object that continually orbits the earth or some other space body.o They gather information about the bodies they orbit.o The world’s first artificial satellite, Sputnik 1, launched by the Soviet Union in 1957.

TYPES OF ARTIFICIAL SATELLITES

1. Research Satellites measure fundamental properties of outer space.

2. Weather Satellites help scientists study weather patterns and forecast the weather.

3. Communication Satellites provide a worldwide link up of radio, telephone and television.

4. Navigation Satellites are mainly intended to help determine the positions of aircraft, ships and submarines with great accuracy.

5. Earth Observation Satellites are used to map and monitor our planet’s resources an ever-changing chemical life changes.

SATELLITE MISSIONS

Satellite Missions

CommunucationsNavigationMilitary SurveillanceEarth ObservationAstrophysicsEarth ScienceOther

SATELLITE ORBITS• Satellite orbits have a variety of shapes.• The greater the altitude, the longer the orbital period.• In terms of altitude, satellites are classified as:i. Low earth orbit satelliteii. Middle earth orbit satelliteiii. Geostationary earth orbit satellite

LOW EARTH ORBIT (LEO)LEO satellites have a small area of coverage.They are positioned in orbit approximately 3000km from the surface of the earth.They complete one orbit every 90 minutes.ADVANTAGESReduces transmission delay.Eliminates need for bulky receiving equipment.DISADVANTAGESSmaller coverage area.Shorter life span (5-8yrs).

MEDIUM EARTH ORBIT (MEO)

MEO satellites have orbital altitudes between 3000 and 30,000 km.

MEO’s are placed in an elliptical (oval-shaped) orbit.

ADVANTAGES Radio signals sent from a satellite at

medium altitude can be received over a large area of earth’s surface.

The stability and wide coverage of the orbit make it ideal for navigation satellites

GEOSTATIONARY EARTH ORBIT (GEO)

o GEO satellites are positioned over the equator.o The orbital altitude is around 30,000-40,000 km.o The orbit is synchronous with the earth’s

rotation.ADVANTAGESo Television broadcasts are uninterrupted.o Used to track major developments such as

hurricanes 24 hours a day.DISADVANTAGESo It takes longer for the signal to get to earth and

back to satellite.o Increased difficulty of telephone conversations.

APPLICATIONS OF ARTIFICIAL SATELLITES

They record changes in earth and its atmosphere.

It helps transfer telephone calls over the oceans.

They have also orbited the moon, the sun, asteroids and the planets. Such satellites mainly gather information about the bodies they orbit.

It helps support military activities.It helps monitor crops and other

resources.

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