How are the satellite cloud images on TV taken?

Weather forecast programs are broadcast on TV every day. The cloud images transmitted from meteorological satellites demonstrated on the screen reflected the changes in the earth's weather. They were intuitive and dynamic and were widely welcomed by the audience. This shows that meteorological satellites have entered the homes of millions of ordinary people.

Meteorological satellites can be divided into two categories according to their orbits: polar-orbiting meteorological satellites and geostationary meteorological satellites.

Polar-orbiting weather satellites are named because their orbits pass through the North and South Poles every time they orbit the earth. Its orbit is nearly circular and its altitude is between 700 and 1,000 kilometers. Every time this kind of satellite orbits the earth, the observable ground range is 2,800 kilometers wide from east to west, and it can cover the earth's surface once after 14 orbits. However, it can only conduct meteorological observations twice a day in a certain area, with an interval of 12 hours. Its advantage is that global meteorological data can be obtained, but its disadvantage is that due to the rotation of the earth, the cloud image data is discontinuous.

Geostationary weather satellites are stationary relative to the earth because they rotate around the earth at the same speed as the earth's rotation on the equatorial plane 36,000 kilometers above the earth. It can produce a weather data map covering an area of ??nearly 100 million square kilometers of the earth every half hour. Its advantage is that data can be sent to the ground in a timely manner and it can continuously observe the same area. The disadvantage is that a satellite can only observe 1/3 of the earth's area, and its meteorological observation capabilities in high latitude areas (greater than 55°) are poor.

The two kinds of weather satellites have different purposes, different functions, and their own strengths and weaknesses. They cannot replace each other, but they can complement each other. If these two satellites are combined, an ideal meteorological satellite system can be formed.

The remote sensing instruments installed on meteorological satellites receive various radiations from the "Earth-Atmosphere System" and convert the obtained data into electrical signals, which are transmitted to the ground receiving station through the transmitter and then processed by the computer. After processing, the vertical distribution of atmospheric temperature and humidity, the distribution of water vapor in the upper and middle atmosphere, the distribution and content of ozone and other parameters are obtained. At the same time, data such as visible light cloud images, infrared cloud images and water vapor images are obtained. These are the satellites we see on TV. Cloud Atlas.

With satellite cloud images, it not only makes up for the shortage of meteorological observation points in oceans, mountains and desert areas, but also can intuitively monitor changes in various weather systems and gain insight into various ongoing disasters. Processes, such as plum rains, typhoons, heavy rains and cold waves, etc.

Currently, more than 100 meteorological satellites have been launched worldwide. my country has launched "Fengyun-1" (polar orbit) and "Fengyun-2" (stationary) in 1988 and 1997. ) two kinds of meteorological satellites, which are overlooking the motherland and play an important role in my country's meteorological application research.