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Introduction of Remote Sensing of Satellites
 Previously, you have already appreciated the gorgeous picture of lakes by the satellite remote sensing. Here, you would have a general idea of the new technique - remote sensing of the satellite, a bird's-eye view of the lake from the sky. Also, you will be taught how to discern those multicoloured pictures of lakes by the satellite remote sensing.
Chinese nation is rich in imagination, and in the ancient mythology, there is a story about Chang'e rising to the moon. It is said that after taking an elixir of life, Chang'e floated up from the ground, and flew directly to the Moon Palace. Later, Wugang and a little hare also came to the moon. When the white moon hangs up in the sky at a fine night, you can find there is a shadow in the moon. The shadow looks as if Wugang is cutting sweet-scented osmanthus trees and the hare is raising its head to have a look! Li Shangyin, a famous poet in Tang Dynasty, had a poet about Chang'e, "Chang'e should be repentant to steal the elixir, feeling sad for each night in the blue sky." Chairman Mao Zedong wrote in the poem Butterfly Attached to Flower (Replying Li Shuyi), " I lose the blazing sun while you lose the willow, the willow straightens up into the sky. Inquire what Wu Gang can entertain us; Wu steps out, holding osmanthus-fermented wine in both his hands. "
These romantic, bold and unconstrained verses have already come into reality today. The elixir is just the contemporary rocket. Either Chang'e or little rabbit, Wugang are nothing but the satellites sent into the sky by the rocket.
From the ancient times to the present in China, there has been spreading the legends of persons who can see things or hear voices a long way off. In many temples, their statues are molded.
Today, science and technology are extremely developed. Scientists can load on the satellite the scientific instruments, which can observe the earth from the remote space through electronic scanning or optics photographing. Mankind has already realized their dreams of thousands of years. It is called "remote sensing" for this kind of technique of observing and perceiving objects from the remote space without touching the objects. The relative techniques of utilizing scientific instruments loaded on the satellite and realizing observation and technical control of the earth are called satellite remote sensing technology.
Now, let's have a general review of some nouns about " remote sensing."
Remote Sensing
As its name suggests, " remote sensing" means sensing from far away. With the aid of special survey instrument, electromagnetic wave signals radiated (or reflected) from the remote objects are incepted and recorded, and transformed into the pictures that human eyes can discern directly through processing, so that the nature and movement regularities of the object surveyed are revealed.
Remote Sensing Platform
Remote sensing platforms can be divided into two categories: spaceflight and aviation platforms. The spaceflight platforms include spaceships, satellites, and rockets, and the aviation platforms have balloons, and planes. In addition, there are also remote sensing vehicles, etc. All these aircrafts are called remote sensing platform.
Theoretical Foundation of Remote Sensing
Remote sensing technology and application are based on the theories of physics, mathematics, geography, and biology.
(1) Physics foundation: Remote sensing takes use of theory of the electromagnetic waves of ground objects to discern the target.
(2). Mathematics foundation: Remote-sensing pictures must follow strict mathematics rules, treated with according to certain space coordinates, projection, and scale.
(3). Geography and biology foundation: Remote sensing information is drawn and discerned in accordance with the principles of geography and biology.
Resolution of Remote Sensing Information
The remote sensing information is decided by three kinds of resolutions: spectrum resolution, space resolution and time resolution.
(1). Spectrum resolution is generally determined by remote sensing instruments, and divided into panchromatic spectrum (Black-and-white spectrum) and multi-spectrum spectrum (4, 7 or more).
(2). Space resolution: ground subjects are reflected as the image spots. Whereas, we can say each image spot on the picture represents certain area on the ground. Now what are commonly used are: Landsat TM, 30mx30m; multi-spectrum SPOT,20mx20m; the panchromatic film, 10mx10m; India earth resources satellites, 5mx5m, etc.
(3). Time resolution means the interval that the satellite passes through one spot on the earth, namely how much time to obtain new information repeatedly. Now the commonly used are 18 days, 9 days and 5 days, etc., and they play a significant role in analyzing dynamic changes of ground subjects and environmental monitoring.
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