摘要
利用太阳照射的漫射板在反射波段(400～2500nm)对星载多光谱遥感器进行飞行中定标是一种高精度的定标技术。文中介绍了一种以太阳照射的漫反射板为基准源的星上定标系统的工作原理及基本结构,它由漫反射板、漫反射板监视器及衰减屏几部分组成。遥感器通过其成像光学系统对漫反射板的观察实现绝对定标,漫反射板监视器用于监视漫反射板输出波段辐亮度的长期稳定性,衰减屏的合理设置则确定了系统的工作点,目的是提高定标精度及监视精度。论文重点讨论了有关这几部分的技术要求。经过分析认为:用烧结法加工的聚四氟乙烯板较好地满足了星上定标的要求;由漫反射板监视器可以获得漫反射板输出波段辐亮度及太阳常数短期内变化的信息,这对地物目标观测数据的处理有一定参考价值;结合Sea WiFS的光谱通道及海色数据对确定系统工作点的衰减屏Ⅰ的透射率进行了计算,结论是透射率0.08较为合理;为提高漫反射板监视器的监视精度,经计算,衰减屏Ⅱ的透射率选为0.02;此外,对星上定标工作模式也作了定性的探讨。
In this paper, a kind of on - board calibration assembly using a reflective solar - illuminated diffuser as a standard source in the reflective region of the spectrum is described. The calibration assembly makes up mainly of a full - aperture and full field - of -view solar diffuser, an integrating sphere to serve as the solar diffuser stability monitor and two transmitting screens to weaken the incident solar energy, Once per orbit, at one of the Earth' s poles, the sun' s radiation strikes the diffuser, By knowing the reflectance properties of the diffuser, it is possible to accurately predict the radiance of the diffuser for absolute radiometric calibration of reflective bands. Solar- illuminated diffuser data is only accepted as valid when the satellite is over the dark side of the terminator; this limits the amount of stray light entering the sensor through the Earth - scan viewport during the calibration interval. The solar diffuser with high spectral reflectance fabricated from sintered polytetrafluoroethylene (PTFE) exhibits optimum Lambertian Property, so it' s an accurate radiance target for the calibration. The soiar diffuser stability monitor alternately views the solar diffuser and the sun, providing a check of the diffuser to monitor reflectance stability and detect the presence of any contaminants. Additionally, we may obtain information on solar constant which will be valuable to data processing. The transmissivity of transmitting screen I determines the radiance of the solar diffuser. Based on the specifications which the Sea - viewing Wide Field - of - view Sensor (SeaWiFS) meets, the transmissivity of transmitting screen I is calculated. The result shows it can' t be more than 0. 10, conveniently, it may be 0.08. Another calculation on the transmissivity of transmit- ting screen Ⅱ shows that it had better to be 0.02 to monitor the stability of the solar dif-fuser more precisely. The goal of the study in this paper is to calibrate space - borne mul-tispectral sensors in the reflective bands with an absolute accuracy of 5% .
出处
《航天返回与遥感》
1996年第4期14-21,共8页
Spacecraft Recovery & Remote Sensing
关键词
遥感器
星上定标
漫反射
星载
多光谱
Remote sensor On - Board calibration Diffuse reflection
