Have you ever heard of the satellite(卫星) called the Early Bird, which was built by a group of scientists from 14 countries? Up till now dozens of satellites have been put into _________and they help people in many ways.

You can speak to people on the other side of the world over the telephone with the help of a satellite. They can help to take the photos of the earth and other _________. Some pictures taken by the satellites show us the right places where different metals can be _________. They can also tell the difference between healthy plants and poor ones. This is a great _________to the scientists who work in the forests and in agriculture(农业).

Satellites are quite useful in our daily life. For example, satellites for _________ are used to send radio and TV programs from one part of the world to another. It is the satellites that make our world seem _________.

A number of research stations have been set up to study the outer space. In the past, it was difficult for the scientists to get a _________picture of space because of the dusty air, _________ satellites make it easier. They are being used more and more to _________ information about space just like _________between space and men.