Abstract. An environmental trace gases monitoring instrument (EMI) is a nadir-viewing wide-field imaging spectrometer, which aims to quantify the global distribution of tropospheric and stratospheric trace gases, and is planned to be launched on 9 May 2018. The selected wavelength bands for EMI are ultraviolet channels: UV1 (240–315 nm), UV2 (311–403 nm) and visible channels: VIS1 (401–550 nm), and VIS2 (545–710 nm). The spectral resolution is 0.3–0.5 nm, and the swath is approximately 114∘ wide to achieve a one-day global coverage. The preflight calibration of the EMI is discussed in this paper. A tunable laser and rotating platform are adopted for an EMI wavelength calibration of the entire field of view. The accuracy of the wavelength calibration is less than 0.05 nm. In addition, the solar calibration mode shows the same results compared with Earth observation mode. A thermal vacuum test is performed to investigate the influence of in-orbit thermal vacuum conditions on the EMI, and EMI spectral response changes with pressure, optical bench temperature, and charge-coupled device (CCD) detector temperature are obtained. For a radiometric calibration of UV1, a diffuser plate with a 1000 W xenon lamp, which produces sufficient UV output, is selected. An integrating sphere system with tungsten halogen lamp is selected for the UV2, VIS1, and VIS2. The accuracies of radiance calibration are 4.53 % (UV1), 4.52 % (UV2), 4.31 % (VIS1), and 4.30 % (VIS2). The goniometry correction factor and irradiance response coefficient of the EMI are also calibrated on the ground for an in-orbit calibration of the solar. A signal-to-noise ratio (SNR) model of the EMI is introduced, and the EMI in-orbit SNR is estimated using the SNR and MODTRAN radiance models.

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Two strength mooring chain steels were used to investigate the stress corrosion cracking (SCC) in synthetic seawater. The resistance of both strength steels to SCC was similar in neutral synthetic seawater. But the failure mechanism was different. For lower strength steel, it is mainly induced by anodic dissolution, while for higher strength steel, by hydrogen embrittlement. The reason was elucidated from their microstructures and corrosion characteristics.

The effects of grain boundary characters on the morphology evolution of grain boundary carbides in Inconel Alloy 600 with high proportional low Σ coincidence site lattice (CSL) boundaries aged at 715 oC for 1-100 h were investigated by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). During the aging process, the carbides precipitated at coherent twin (Σ3) boundaries are very few and finest within all the aging time. Bar like carbides precipitated near both sides of the incoherent twin (Σ3) boundaries, and bigger carbides than that of coherent Σ3 boundaries had been found on the incoherent Σ3 boundaries. Bar like carbides precipitated near only one side of Σ9 boundaries, and much bigger carbides than that of Σ3 boundaries have been found on the Σ9 boundaries. The morphology of carbides precipitated at Σ27 and random grain boundaries are similar, and is bigger than that of precipitated at other grain boundaries. The carbides precipitated at grain boundaries with all types grow bigger with the aging time prolonging, but their growth rates are different.