Abstract. The short-wave infrared (SWIR) bands (5 to 7, 26) of Terra Moderate Resolution Imaging Spectroradiometer (MODIS), which are colocated with the midwave infrared bands (20 to 25) on the short- and mid-wave infrared focal plane assembly, have a known issue related to 5.3-μm out-of-band (OOB) thermal leak and electronic crosstalk that was identified prelaunch. As a result, a crosstalk correction algorithm was designed and implemented in the MODIS level 1B (L1B) calibration. Shortly after the Terra launch, extensive efforts were undertaken to help characterize and mitigate the impact due to the OOB response and crosstalk on the SWIR on-orbit calibration and, consequently, the associated L1B data products. In addition, special night-time-day-mode operations have been regularly scheduled to derive the crosstalk correction coefficients. Since MODIS does not have a spectral band centered at 5.3 μm, its band 28 (7.325 μm) was chosen as the surrogate sending band to simulate the OOB radiances at 5.3 μm. This was largely based on the measurements from the MODIS Airborne Simulator spectrometer field campaigns in the early months after the Terra launch. In the case of Aqua MODIS, the magnitude of the SWIR crosstalk was much smaller and band 25 (4.52 μm) was found to be more effective as the sending band for the crosstalk correction. In recent years, the Terra MODIS photovoltaic (PV) long-wave infrared (LWIR) bands (27 to 30) electronic crosstalk has increased considerably, especially after the spacecraft safe-mode event occurred in February 2016. This accentuated degradation in the PV LWIR performance has also impacted the performance of the SWIR crosstalk correction and thus its calibration and data quality. We examine the use of band 25 as the sending band for the Terra MODIS SWIR crosstalk correction and compare its performance with that based on band 28 as the sending band. Results indicate an improvement of on-orbit gain stability for the SWIR calibration and reduced detector to detector and subframe to subframe striping in the calibrated L1B imagery, especially during the period when the PV LWIR electronic crosstalk has become more severe. This approach has been implemented in the forward production of Terra MODIS Collection 6 and Collection 6.1, starting from July 2019, and is planned to be used for the future reprocessing of MODIS L1B and to help improve the mission-long reflectance calibration and trending stability of the SWIR bands.

中文翻译：

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Terra MODIS 短波红外光谱带带外响应在轨表征的改进

摘要。Terra中分辨率成像光谱仪（MODIS）的短波红外（SWIR）波段（5至7、26）与中波红外波段（20至25）在短、中波红外焦平面上共置组装，具有与 5.3 微米带外 (OOB) 热泄漏和电子串扰相关的已知问题，该问题在发射前已确定。因此，在 MODIS 1B (L1B) 级校准中设计并实施了串扰校正算法。在 Terra 发射后不久，就进行了大量努力来帮助表征和减轻 OOB 响应和串扰对 SWIR 在轨校准以及相关 L1B 数据产品的影响。此外，还定期安排特殊的夜间-白天模式操作以导出串扰校正系数。由于 MODIS 没有以 5.3 μm 为中心的光谱带，因此选择其带 28（7.325 μm）作为替代发送带以模拟 5.3 μm 处的 OOB 辐射。这主要基于在 Terra 发射后的最初几个月中 MODIS 机载模拟器光谱仪现场活动的测量结果。在 Aqua MODIS 的情况下，SWIR 串扰的幅度要小得多，并且发现波段 25 (4.52 μm) 作为串扰校正的发送波段更有效。近年来，Terra MODIS 光伏 (PV) 长波红外 (LWIR) 波段（27 至 30）电子串扰显着增加，尤其是在 2016 年 2 月发生航天器安全模式事件之后。PV LWIR 性能的这种严重退化也影响了 SWIR 串扰校正的性能，从而影响了其校准和数据质量。我们检查了使用频段 25 作为 Terra MODIS SWIR 串扰校正的发送频段，并将其性能与基于频段 28 作为发送频段的性能进行比较。结果表明，SWIR 校准的在轨增益稳定性得到了改善，并且在校准的 L1B 图像中减少了探测器到探测器和子帧到子帧的条纹，尤其是在 PV LWIR 电子串扰变得更加严重的时期。从 2019 年 7 月开始，此方法已在 Terra MODIS Collection 6 和 Collection 6.1 的前瞻生产中实施，