New progress of airborne scanners at sitp from 1986 to 1990

Printer Friendly Format

Page 1 of 2
| Next |

New progress of airborne scanners at sitp from 1986 to 1990

Xue Yongqu, Shen Mingming, Yang Cunwu,
Wang jainyu, Guo Yiping
Shanghai Institute of Technical Physics, Academia Sinica,
Shanghai 200083, China

Abstract
This paper describes some new airborne scanner systems manufactured at SITP in the recent five years. The spectral resolution of the sensors has become higher. The installation of bands is more complete and has formed series. The onboard electronics has made progress on multiple, high speed, large content, automatic operation and flexible function. The ground preprocess facility provides fast reproduction, information transfer, process service, and standard products the Computer Compatible Tape (CCT). The whole system lays stress on total effect, generalization and standardization. And standardization. A fair technical system with complete units from getting data to standard products in multispectral remote sensing has been formed. Some typical applications are also introduced here.

Introduction
Since 60's, the SITP has obtained a big achievement in scanning image based on the infrared detect technology. Some infrared image systems were successfully made. Because of the research ability in optical remote sensing, the SITP has been taking part in some important plan on scientific and technology. The airborne spectral scanner DGS completed in 1986 was the representative work in that period. Since 1986 the study of airborne optical remote sensing instruments has developed in quality and range. this paper introduces the development of airborne scanners at the institute during recent five years and some application examples.

Sensors
There are two developing directions for the sensor.
One is in the technology itself. The spectral bands should be more complete. The spectral resolution and space resolution should be higher. The instrument will be developed towards resolution and space resolution should be higher. The instrument will be developed towards image spectrometer. The AMS has 16 bands in VIS/NIR and 3 bands corresponding to the 5th, 6th, 7th, CH of TM. The thermo-infrared multispectral scanner TIMS with 7 bands in the range of 8.2-12.2 micron was also manufactured. Through pre-research a test model of image spectrometer 64 CH VIS/NIR SCANNER is being built which is convenient for practical application for its large total FOV.

The second direction is in the specialization of instruments. we had finished the UV/IR 2 CH ACANNER for sea pollution monitoring and the VIS/NIR 3CH SCANNER for forest fire detecting.

Tab. 1 shows the specifications of these scanners and a comparison with the scanner DGS.

Scanners Completed in 1986-1990
Table. 1

Sensor	DGS Multi-spetral scanner	19CH AMS	7CH TIMS	64CH Prototype Scanner	UV/IR 2CH Scanner	VIS/NIR/TIR 3CH Scanner
Application	Multipurpose Remote Sensing	Multipurpose Remote Sensing	Multipurpose Remote Sensing	Multipurpose Remote Sensing	Pollusion Monitoring on sea	Forest Fire Detecting
Tot. View of Field	100 degree	90 degree	90 degree	90 degree	100 degree	100 degree
Ins. View of Field	3 mrad	3 mrad	3 mrad	1.5 mrad	3 mrad	3 mrad
Scan Rate (C/S)	25-100	20-50	10-30	10-20	100	100
Optical Area	52cm²	52cm²	200cm²	200cm²	64cm²	52cm²
Focal Length	666m²	666m²,217m²	180m²	180m²	800m²	666, 217m²
Scan Mirror	4 Sided Mirror	4 Sided Mirror	45 Degree Mirro	45 Degree Mirror	45 Degree Mirror	4 Sided Mirror
Working Bands(um)	0.40-0.43 0.43-0.48 0.48-0.54 0.53-0.62 0.60-0.70 0.68- 0.90 3.0-5.0 or TM 1,2,3,4,5,7 ALL 8CH	16 Bands in 0.46-1.1 1.55-1.75 2.08-2.35 8.0-12.5 ALL 19CH	8.2-8.6 8.6-9.0 9.0-9.4 9.4-9.8 9.8-10.6 10.6-11.4 11.4-12.2 ALL 64CH	32 Bands in 0.465-1.1 16 Bands in 1.40-1.82 16 Bands ln 1.98-2.40 ALL 64CH	0.28-0.38 8.0-12.5	0.4-0.8 3-5 8-12.5
Detector & Working Temperature	PMT Insb(77k)	Si Line Array HgCdTe(77k)	Si Line Array HgCdTe(77k) Line array	Si & HgCdTe(77k) Line Array	PMT HgCdTe(77k)	Si HgCdTe(77k)
Record & Display	Multi-Channel Analog Tape, CRT Display, Film Reproducing	Analog Tape, Laser-desk, Multi-colour Real Time Display	Same as Left	Same as Left	Analog TApe, Multi-colour Real Time Display, Film Reproducing	Multicolour Real Time Display Transmission in TV Format
Flying Paramenter	No	Display & Record	Display & Record	Display & Record	Display	Display
On-board Pre-processing	No	Programmable in Bands	Programmable in Bands	Programable in Bands & Space	No	No
Completed Data	1986	1990	1990		1987	1987

19CH Scanner - AMS

The scanner equally divides the spectrum of 0.46 - 1.1 micron into 16 bands. If necessary such bands can be grouped to form some channels of TM, MSS or HRV. Because of the complete bands visible to infrared to scanner is convenient to resources investigation. The optics is shown in Fig. 1. A Kennedy structure, which has high scan efficiency, is used for ground scanning. A two-mirros telescope converges the energy. The optical path is improved: the two split light beam do not meet each other at the symmetry line of the primary mirror , but are separated at a certain distqance, so the effective optical area is increased. For the second mirror, the front surface is coated with a long wave pass film and the rear surface having a curvature is coated with an antireflection film. The infrared focus is formed through the second mirror. The energy left, which is reflected by the second mirror, passes the filters to get all the bands. The radiation in 0.46-1.1 micro enters the spectrometer, is collimated by a parabolic mirro, and falls on the plane plaze grating with a blaze wavelength of 0,7 micro. The detector array is located on the focus position of the converging lens.
7CH Scanner -- TIMS

Having 7CH in thermo-infrared and detecting the spectral feature of rock and mineral, the scanner is useful for geology remote sensing. It uses a slant 45-degree rotative morror for scanning. The main optical unit consists of a primary morror and a collimating mirror. Both of them have a parabolic surface with a common focus at the field stop. Such arrangement is beneficial to block design and assembly of the dispersive unit, and meets the requirement of onboard space. An infrared blaze grating with blaze wavelength of 9.0 micron is used as the disperse element. The converge unit is a specially designed Ge-lens having a FOV of 4.91 degree and F/No of 0.78. The optical diagram and the sizes of the detector array are shown in fig. 2.
VIS/NIR 64CH Scanner Test Model

This pre-research test model for image spectrometer co-uses the main optical unit of TIMS. A. Long wave pass filter separates VIS from NIR. In spectrometer I, with operation band of 0.46-1.1 micron, a concave holographic grating performs dispersing and converging. there is a special filter on the surface of the 32-element Si detector array to remove the high-order spectra. In spectrometer II, designed in 1.46-2.4 micro, the dispersive element is a plane blaze grating having blaze wavelength of 1.6 micron. The grating sways back and forth between two positions synchronously with scan line and stays at each position for a scan line. So the 16 detector elements can cover 32 bands. The rotative angle of the grating is 3.55 degree. The location precision is better than plus and minus 1.5 minute. The rotative rate is not higher than 10 c/s. The system diagram is shown in Fig.3.

All the above-mentioned sensors employ optico-mechanical object space scanning to eliminate the defect of smaller swath in broom brush scanning. It is good for practical air borne remote sensing work. They also have to optical angle encoder to perform a sample in equal angle which is necessary for data processing.

Page 1 of 2
| Next |