TYPES OF SATELLITES

Satellites are usually classified according to the type of orbit they are in. There are four types of orbit associated with satellites, and the type of orbit dictatesa satellite's use.

Low Earth Orbits

Satellites in low Earth orbits are normally military reconnaissance satellites that can pick out tanks from 160 km above the Earth. They orbit the earth very quickly, one complete orbit normally taking 90 minutes. However, these orbits have very short lifetimes in the order of weeks compared with decades for geostationary satellites. Simple launch vehicles can be used to place these satellites of large masses into orbit.

Sun-Synchronous orbits

Meteorological satellites are often placed in a sun-synchronous or heliosynchronous orbit. These satellites are in polar orbits. The orbits are designed so that the satellite's orientation is fixed relative to the Sun throughout the year, allowing very accurate weather predictions to be made. Most meteorological satellites orbit the Earth 15 to 16 times per day.

Geosynchronous satellites

Earth-synchronous or geosynchronous satellites are placed into orbit so that theirperiodof rotation exactly matches the Earth's rotation. They take 24 hours to make one rotation. However, the plane of orbit for these satellites is generally not the equatorial plane. Apart from geostationary satellites (see below), the satellites are used for communications at high latitudes, particularly in Russia and Canada. The orbits are called Molniya orbits. The satellites are placed in highly elliptical orbits which enable them to appear to hover above one point on the Earth for most of the day. In twenty four hours they move over the Earth in a figure of eight pattern centered on a fixed longitude, moving slowly where they can be useful and quickly where they are of little use.

Geostationary satellites

The majority of communications satellites are in fact geostationary satellites. Geostationary satellites like geosynchronous satellites take 24 hours to complete a rotation. However, geostationary satellites are positioned directly over the equator and their path follows the equatorial plane of the Earth. As a result geostationary satellites don't move North or South during the day and are permanently fixed above one point on the equator of the Earth.

Most video or T.V. communications systems use geostationary satellites. Geosynchronous and geostationary satellites are typically orbiting at 35,788 km (22,238 miles) above the surface of the planet (42,000 km from its center).

Modern satellites have a mass of several thousand kilograms, compared with just 180 kilograms for Sputnik. Modern satellites are placed in space using launch vehicles like the Arianne Rocket or the Space Shuttle. Once in space, most satellites obtain their power from the Sun using solar panels. Satellites travelling deep into space often carry additional nuclear power supplies.

Name ______# ______Date ______Hour______

Hours 5/6 Types of Satellites Partner Poster Activity

(50 point Formative Assessment)

Part I Directions: Read the article "Types of Satellites” and answer the following questions.

_____ 1. Identify the object that is NOT a natural satellite:

a. the Earth’s moonc. the Moons of Jupiter

b. The International Space Stationd. asteroid debris

_____ 2. How are satellites classified?

a. type of orbitc. composition

b. sized. distance from Earth

3. Most TV or communications systems use ______.

4. If a satellite orbits the Earth 15 times a day; how long does it take to make one orbit? ______

______

5. Describe satellites in low earth orbits: ______

______

______

6. If a satellite is in a sun-synchronous orbit, what does that mean? ______

______

______

7. If a satellite is in a geosynchronous orbit, what does that mean? ______

______

______

8. How high is a geostationary satellite above the center of the Earth?______

______

9. What are geosynchronous satellites used for? ______

______

10. What is the primary difference between a geostationary and a geosynchronous satellite? ______

______

______

Teacher check-in ______

Part II Directions: Get a computer and follow the steps listed below:

1. Decide which type of satellite interests you the most and circle it:

weathercommunicationbroadcastscientific

navigationalearth observationrescuemilitary

2. Use the Internet to find a specific example of the type you circled and write it here: ______

3. Circle the type of orbit your satellite has (might be a combination of two)

Natural GeosynchronousGeostationarySunsynchronous

Teacher check-in ______

Part III Directions: You and your partner will create a poster that includes all of the questions asked and the objectives listed in the rubric below.

Objective or
Question / Points Possible / Student Checklist / Points Earned
Your names, numbers, the date and the hour are on the front of the poster / 2
Your title is what you wrote in question #2 above / 3
The type of orbit is identified (question #3) / 5
How did this satellite get placed into orbit? / 5
Why does this satellite stay in Earth’s orbit? / 5
What keeps this satellite from flying into space or crashing into Earth? / 5
If this satellite appears stationary, why? / 5
What is the revolution period/ orbiting time of this satellite? / 5
The poster is illustrated, neat, and colorful / 5
There are no spelling or grammar errors / 5
Part I of this activity is complete and correct / 5

Points Earned: ______

50