The Development of Remote
Sensing Instruments in the Chinese Academy of Sciences
Liu Yue-guang The Space Science and Technology Centre, The Chines Academy of Science Deputy Chief Engineer Introduction China has a vast territory and a varied topography with rich natural resources. In order to speed up “ the four modernizations”. The broad scientific and technical workers have devoted themselves to exploiting and making full use of the natural resources of their country. Since the early 1970’s, the Chinese Academy of Sciences (CAS) has paid great attention to remote sensing technology. Some institute of CAS has created favourable conditions and done lot of work in studing the fundamental research of remote sensing developing instruments, image processing technology and field experiments, etc. They have got a lot of aerial remote sensing data about the subtropical plateaus, the scabcaches, the deltas of the esturies, the plains and the deserts. Doing all this, not only entiched our technical knowledge of remote sensing but also solved many problems in agriculture, forestry, geography, water resources, etc. As the satellite remote sensing technology in our country is still at the preparatory stage, this article is only about the outline of the main aspects of the remote sensing. II. Aerial Multispectral Instruments 1. The Aerial Multispectral Camera The Aerial Multispectral Camera has been developed by the Changchun Institute of Optic and Fine Mechanics. In several times of aerial remote sensing experiments, it has taken a lot of high quality multispectral images. The camera has four channels (lenses) and five spectral bands (the blue band may change into ultraviolet band it required). The focus length of the lenses is 100mm; the resolution is 50 lines/mm; and the speed height ratio (V/H) range is 0.007-0.07. Some institute and colleges have installed the 135-camera into simple 4- and 6-spectral cameras. These cameras are used in the mcasurement of spectrum of ground scene. 2. The Multispectral Scanner In the past few years, the Shanghai Institute of Technical Physics has developed and put in operation five kinds of instrument. These instruments and their specifications are mentioned below: 2-1. The Aerial 9-Channel Scanner Wave ranger: 0.4 – 14 mm Sensitivity: 0.15 – 5% Field of view: 90% Instantaneous field of view: 3mrad. Speed-height ratio (V/H) range: 0.01-0.075rad./sec. 2.2. The Visible and infrared Scanning Rediometer This instrument consists of two single wave band infrared scanning radiometers. Operating wave length. 0.4 – 1.1 um and 8 – 14 mm Field of View : 1200 Instantanceous field of view : 3.6 mrad. Scanning speed: 120 lines/min. or 400 lines/min Sensitivity in visible spectrum: (better than) 7x10 – 11 w/cw2 Temperature resolution in infrared spectrum: (better than) — 0.10 c 2-3 The Aerial Infrared 6-Channel Scanner Wave range: 8 — 14 mm Field of view: 600 Instantaneous field of view: 2 mrad. V/H range: 0 — 0.0725 rad./sec. 2-4. The Aerial Infrared 2-Channel Scanning Camera Wave range: 3—5µm or 8 — 14 µm Field of view: 1000 Instantaneous field of view: 0.52 or 1.04 mrad. V/H range: 0—3.12 rad. Min. 2-5. The Low-Altitude High Resolution Infrared Scanning Camera Wave range: 8 — 14µm Field of view: 1000 Instantaneous field of view: 0.65 mrad. Max. V/H: 1.11 rad./sec. The ground resolution of this instrument is much higher (at the height of 300 meters, the ground resolution is 0.2m). All of the above instruments are equipped with tape recorders or film recorders. Some institutes have also developed JHY 2-Band Infrared Scanners and 12-badn visible and Infrared Scanning Radiometers. III. The Spector-radiometer for Spectro-ignature Investigation of Ground Objects The purpose of the research of spectral signatures of ground objects is to provide scientific basis for designing and manufacturing remote sensing instruments and for image analysis. We paid attention to this at the very beginning of the work. We held a scminar on the results of testing spectro-radiometric instruments in 1979. During the discussion, we tested 17 instruments with five different types. Their spectral range is from visible spectrum to near infrared, and the instrument which may reach far infrared and microwave will be developed in the near future.
During 1970’s, the government agencies in China began to use the Landsat imagery. They also have carried out many times of aerial remote sensing experiments. That impelled them to develop their own image analysis technology. Now they have the capability to carry out their work depending on their own technology and equipments. The following instruments and systems have been developed. 1. The False Color Image Compositer The Changchun Institute of Optics and Fine Mechanics developed a 4-band Flase Color Compositer. A half achromatic lens with the focus length 200 mm is used as the projective lens. The relative aperture is 1:5.6. the image can be enlarged to 5 times the 70 mm aerial photographic film or Landsat images can be used the secreen size is 300 x 300 mm. And the non-uniformity fo illumination is less than 20% The type JY Horizontal 3-Channel Color Compositer was designed and manufactured by the Chengdu Scientific Instrument Factory. The focus length of the projective lens of the compositer is 180mm, the relative aperture is 1: 4.5 the size of the projective screen is 430 x 455mm, and the non-uniformity of illumination is less than 20%. By the way, some simple version of 3-channel color compositers were designed and manufactured by other colleges and factories. 2. Pseudo Color Density Slicer Five different types of pseudo color density slicers were designed and manufactured by eight colleges and factories co-operatively. They have been used in processing of the cloud map of meteosatellite and landsat images. 3. Digital Image Processing System since 1973, CAS has begun to develop the digital image scanning system. The system was consisted of the electronic color separative scanning digitizer and the drum typeplotter which are connected to the digital computer through a controller. The black and white and color images or the graphics both transparent film and reflected photographs can be digitized. Various kinds of digital image processing systems have been developed in our country, e.g. the colleges, universities and institute have built TV camera image digitizer, flying spot image input device, analog tapes, moving window display devices, etc. which were connected to some chines made minicomputer systems. The software packages for remote sensing application are now in developing. V. The Microwave Remote Sensing Technology Now it is known that the microwave remote sensing technology is an indispensable part of the remote sensing technology. The microwave remote sensing and the infrared remote sensing may supplement each other. The Beijing Institute of Electronics and the Changchun Institute of Physics under CAS have begun to develop the airborne sidelooking radar and the airborne scanning microwave radiometer and have made some a chievements. It is expected that the airborne side-looking radar will be tested in near future. The 3cm and 10 cm airborne scanning microwave radiometer has tested at the dcsert area, subtropical plateau plain, and beaches and got very good results. VI. Conclusion As mentioned in the introduction, remote sensing technology is very important in exploiting the natural resources of our country. Therefore, the government of China has paid great attention to all kinds of work on emote sensing carried out all over the country. All the work are planned by the National Commission of Science and Technology. Co-operative activities and application of advanced technology are encouraged by the commission. Some of the following are being carried on and some of them will be carried on in China:
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