Calibration Of AOTF Imaging Spectrometer In Deep-space Exploration Application

Spectrum detection is one of the major methods of material analysis. Calibration is a necessary process before application of the spectrometer. Researches on spectral calibration, radiometric calibration as well as system assessment began since the1980s, when imaging spectrometer was invented on the basis of multispectral remote sensing imaging technology. In the1990s, the application of a new dispersion component, Acousto-Optic Tunable Filter (AOTF), on aerospace spectrum detection, was identified as the most significant progress on spectrometers. It is also called the5th generation spectroscopic techniques. AOTF alters the wavelength of the output diffraction spikes according to the input radio frequency driving signal. With its qualities of minimized volume and weight, programmability, fast response, high stability and integrity as well as good environment adaptation ability, AOTF gains preferable advantages in deep space application.Researches on development of AOTF-based spectrometers had a late start in China, especially on space applications. For deep-space spetrum detection usages, developments of AOTF imaging spectrometers are under way, which is in great demand of systematic calibration technologies for deep-space application. In this essay, the calibration methods of AOTF imaging spectrometers for deep-space application was taken as a research object, the quality assessments of new-type AOTF spectrometers and the response characteristics in a wide-temperature space environment were studied, and detailed analyses on principles of gaze-type imaging, radio frequency modulation spectrometer and temperature effect are given. On the ground of the results, the theoretical basis of spectral and radiometric calibration and pre-processing of data as well as a pragmatic engineering method are built up.The main direction and innovations of this research are shown as follows:1. The systematic calibration method and practical implementation of AOTF imaging spectrometer on a deep-space detection background.Based on the principles of AOTF and its characteristics of space application, calibration methods of AOTF spectrometers were set up, and corresponding calibration equipments were developed. The actual application of them on the development and calibration of VNIS(VIS-NIR Imaging Spectrometer)on moonface detection has verified the effectivity of the methods and equiments. This calibration method is an innovation in the sense that it has never been mentioned in any references across the world.2. A fine testing method of the new-type AOTF electrooptic characteristics and equipment development.On the basis of a detailed analysis of AOTF characteristics, a fine testing method of the new-type AOTF electrooptic characteristics were designed, promoting the development of AOTF performance analysis system. They were not only used on the systematic calibration of VNIS, but also applied in the design and producing process of AOTF devices in China. This is an innovation in the sense of a more advanced method and a better quality of assessment.3. The response characteristics of AOTF imaging spectrometer in a complex temperature environment and its pre-processing model.Utilizing the electrooptical response model of AOTF SWIR imaging spectrometer, after analyzing and verifying the temperature characteristics of infrared detectors and AOTF, a the mathematical model of temperature effect on AOTF spectrometer in a complex temperature environment was set up. Pre-processing models and corresponding softwares were built up, and the feasibility and effectivity of the model were verified by tests. This model has not been found in any reference at home and abroad.All in all, researches on the systematic calibration methods of AOTF imaging spectrometer has not provided technological supports for deep-space detection on planets such as the moon, Mars and Venus, but also given scientific basis of the spectrometer development and spetral analysis for applications like soil and water pollution, agriculture, medicine and food, enriching the methods and theories of imaging spectrometers.