Abstract
The environmental trace gas monitoring instrument (EMI) is a space-borne imaging spectrometer onboard GaoFen-5, which was launched in May 2018, covering wavelengths in the range of 240–710 nm to measure NO2, O3, HCHO, and SO2. An advanced EMI-2 instrument with a higher spatial resolution and sufficient signal-to-noise is currently planned for launch on the GaoFen-5(02) satellite in 2021. The EMI-2 instrument bidirectional scattering distribution function (BSDF) is obtained from the absolute irradiance and radiance calibration on-ground. Based on EMI-2 earth and sun optical paths, the key factors of BSDF parameters are introduced. An NIST-calibrated 1000 W FEL quartz tungsten halogen lamp and a 2D turntable are adopted for the absolute irradiance calibration. A large aperture integrating sphere system is used for the absolute radiance calibration. Based on absolute irradiance and radiance calibration functions, the BSDF parameters are obtained, with accuracy of 4.9% for UV1, 4.3% for UV2, 4.1% for VIS1, and 4.2% for VIS2. The on-ground measurement results show that the reflectance spectrum can be calculated from BSDF parameters. On-orbit application of the EMI-2 instrument BSDF are also discussed.
Highlights
QVD is used frequently to provide a solar reference spectrum, and F4 is used on a long-time basis to monitor QVD degradasolar reference spectrum, and F4 is used on a long-time basis to monitor QVD degradation
environmental trace gas monitoring instrument (EMI)-2 instrument bidirectional scattering distribution function (BSDF) is obtained by preflight calibration and mainly used to calculate earth reflectance spectrum
Environmental trace gas monitoring instrument-2 (EMI-2) instrument BSDF is used as key input parameter for the
Summary
The environmental trace gas monitoring instrument (EMI) onboard GaoFen-5 was launched in May 2018, its on-orbit performance was discussed in [1], and the trace gas products (NO2 , O3 , and SO2 ) were introduced in [2,3,4,5]. The Environmental trace gas monitoring instrument-2 (EMI-2) is an improved version of EMI, which is a nadir-viewing push-broom imaging spectrometer, and is currently planned for launch on GaoFen-5(02). EMI-2 and EMI have a descending node equator crossing time of 10:30 and an ascending node equator crossing time of 13:30, respectively. These two instruments have the same altitude of approximately 705 km and can be networked for remote sensing
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