Fluorescence Imaging Spectrometer (FLORIS) for ESA FLEX Mission
Fluorescence Imaging Spectrometer (FLORIS) for ESA FLEX Mission
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DOI：
10.3390/rs9070649
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发表时间：
2017-07-01
期刊：
影响因子：
5
通讯作者：
Drusch, Matthias
中科院分区：
文献类型：
--
作者：
Coppo, Peter;Taiti, Alessio;Drusch, Matthias
荧光探测器（FLEX）任务被选为欧空局的第8个地球探测任务。该任务的主要目标是提供植被荧光、实际光合活性和植被胁迫的全球估计。FLEX将与Sentinel-3串联飞行，提供大气特征和校正、植被相关光谱指数和地表温度的辅助数据。这份手稿的目的是展示它的科学有效载荷，FLORIS，这是一个推扫帚高光谱成像仪，在一个中等大小的平台上飞行。FLORIS将以中等空间分辨率（300米）在150公里范围内测量500纳米至780纳米光谱范围内的植被荧光。它配备了一个非常高光谱分辨率（0.3 nm）的成像光谱仪，用于测量两个氧吸收波段（O-2A和O-2B）内的荧光光谱，另一个光谱分辨率较低的光谱仪用于获得额外的大气和植被参数。紧凑的光机械解决方案是当前仪器的基准。偏振扰频器放置在普通屈光望远镜前，为两个光谱仪服务，以最小化偏振灵敏度。望远镜将地面场景成像到双缝组件上。辐射以光谱方式分散到光栅光谱仪的焦平面上。杂散光的抑制是保证荧光测量精度的关键因素。绝对辐射校准是通过观察一个专用的太阳照射朗伯扩散器来实现的，而光谱校准是通过替代技术在飞行中进行的。热稳定是通过使用两个被动散热器直接看着冷空间来实现的，通过一个闭环系统中的加热器来平衡。焦平面是基于定制开发的ccd。光机械设计坚固，抗温稳定，易于对准。最近对一个优雅的面包板进行的最新测试表明，光学质量非常好。科学数据产品包括大气顶部（TOA）辐射测量以及荧光估计和与植被健康状况有关的高级产品，涉及从农业到林业和气候的广泛应用。
The Fluorescence Explorer (FLEX) mission has been selected as ESA's 8th Earth Explorer mission. The primary objectives of the mission are to provide global estimates of vegetation fluorescence, actual photosynthetic activity, and vegetation stress. FLEX will fly in tandem formation with Sentinel-3 providing ancillary data for atmospheric characterization and correction, vegetation related spectral indices, and land surface temperature. The purpose of this manuscript is to present its scientific payload, FLORIS, which is a push-broom hyperspectral imager, flying on a medium size platform. FLORIS will measure the vegetation fluorescence in the spectral range between 500 nm and 780 nm at medium spatial resolution (300 m) and over a swath of 150 km. It accommodates an imaging spectrometer with a very high spectral resolution (0.3 nm), to measure the fluorescence spectrum within two oxygen absorption bands (O-2A and O-2B), and a second spectrometer with lower spectral resolution to derive additional atmospheric and vegetation parameters. A compact opto-mechanical solution is the current instrument baseline. A polarization scrambler is placed in front of a common dioptric telescope serving both spectrometers to minimize the polarization sensitivity. The telescope images the ground scene onto a double slit assembly. The radiation is spectrally dispersed onto the focal planes of the grating spectrometers. Special attention has been given to the mitigation of stray-light which is a key factor to reach good accuracy of the fluorescence measurement. The absolute radiometric calibration is achieved by observing a dedicated Sun illuminated Lambertian diffuser, while the spectral calibration in flight is performed by means of vicarious techniques. The thermal stabilization is achieved by using two passive radiators looking directly to the cold space, counterbalanced by heaters in a closed loop system. The focal planes are based on custom developed CCDs. The opto-mechanical design is robust, stable vs. temperature and easy to align. The optical quality is very good as recently demonstrated by the latest tests of an elegant breadboard. The scientific data products comprise the Top Of Atmosphere (TOA) radiance measurements as well as fluorescence estimates and higher-level products related to the health status of the vegetation addressing a wide range of applications from agriculture to forestry and climate.