1 . A satellite is an object in space that orbits around another. It has two kinds — natural satellites and artificial satellites. The moon is a natural satellite that moves around the earth while artificial satellites are those made by man.
Despite their widespread impact on daily life, artificial satellites mainly depend on different complicated makeups. On the outside, they may look like a wheel, equipped with solar panels or sails. Inside, the satellites contain mission-specific scientific instruments, which include whatever tools the satellites need to perform their work. Among them, high-resolution cameras and communication electronics are typical ones. Besides, the part that carries the load and holds all the parts together is called the bus.
Artificial satellites operate in a systematic way just like humans. Computers function as the satellite’s brain, which receive information, interpret it, and send messages back to the earth. Advanced digital cameras serve as the satellite’s eyes. Sensors are other important parts that not only recognize light, heat, and gases, but also record changes in what is being observed. Radios on the satellite send information back to the earth. Solar panels provide electrical power for the computers and other equipment, as well as the power to move the satellite forward.
Artificial satellites use gravity to stay in their orbits. Earth’s gravity pulls everything toward the center of the planet. To stay in the earth’s orbit, the speed of a satellite must adjust to the tiniest changes in the pull of gravity. The satellite’s speed works against earth’s gravity just enough so that it doesn’t go speeding into space or falling back to the earth.
Rockets carry satellites to different types and heights of orbits, based on the tasks they need to perform. Satellites closer to the earth are in low-earth orbit, which can be 200-500 miles high. The closer to the earth, the stronger the gravity is. Therefore, these satellites must travel at about 17,000 miles per hour to keep from falling back to the earth, while higher-orbiting satellites can travel more slowly.
1. What is Paragraph 2 of the text mainly about?| A．The appearance of artificial satellites. | B．The components of artificial satellites. |
| C．The basic function of artificial satellites. | D．The specific mission of artificial satellites. |
| A．Providing electrical power. | B．Recording changes observed. |
| C．Monitoring space environment. | D．Processing information received. |
| A．By relying on powerful rockets to get out of gravity. |
| B．By orbiting at a fixed speed regardless of gravity’s pull. |
| C．By changing speed constantly based on the pull of gravity. |
| D．By resisting the pull of gravity with advanced technologies. |
| A．They are more affected by earth’s gravity. |
| B．They take advantage of rockets more effectively. |
| C．They have weaker pull of gravity in higher orbits. |
| D．They are equipped with more advanced instruments. |
