Abstract
Recent investigations have discovered that Terra MODerate-resolution Imaging Spectroradiometer (MODIS) long-wave infrared (LWIR) photovoltaic (PV) bands, bands 27–30, have strong crosstalk among themselves. The linear model developed to test the electronic crosstalk effect was instrumental in the first discovery of the effect in Terra MODIS band 27, and through subsequent investigations the model and the correction algorithm were tested further and established to be correct. It was shown that the correction algorithm successfully mitigated the anomalous features in the calibration coefficients as well as the severe striping and the long-term drift in the Earth view (EV) retrievals for the affected Terra bands. Here, the examination into Aqua MODIS using the established methodology confirms the existence of significant crosstalk contamination in its four LWIR PV, although the finding shows the overall effect to be of lesser degree. The crosstalk effect is characterized and the crosstalk correction coefficients are derived for all four Aqua LWIR PV bands via analysis of signal contamination in the lunar imagery. Sudden changes in the crosstalk contamination are clearly seen, as also in the Terra counterparts in previous investigations. These sudden changes are consistent with the sudden jumps observed in the linear calibration coefficients for many years, thus this latest finding provides an explanation to the long-standing but unexplained anomalies in the calibration coefficients of the four Aqua LWIR bands. It is also shown that the crosstalk contamination for these bands are of similar level for the two MODIS instruments in the early mission that can lead to as much as 2 K increase in brightness temperature for the affected bands, thus demonstrating significant impact on the science results already started at the early going. As Aqua MODIS is a legacy sensor, the crosstalk correction to its LWIR PV bands will be important to remove the impact of the crosstalk contamination from its calibration results and the associated science products.
Highlights
The MODerate-resolution Imaging Spectroradiometer (MODIS) instruments on board the Terra and Aqua spacecrafts have successfully completed more than 16 and 14 years of on-orbit flight, respectively [1,2]
We focus on the sending-band detector-averaged crosstalk coefficients derived from the lunar observations
An examination of Aqua MODIS has confirmed the existence of significant crosstalk
Summary
The MODerate-resolution Imaging Spectroradiometer (MODIS) instruments on board the Terra and Aqua spacecrafts have successfully completed more than 16 and 14 years of on-orbit flight, respectively [1,2]. The crosstalk correction has been applied to the quarterly BB warm-up–cool-down (WUCD) and the routine scan-based BB calibration as well as the MODIS Level-1B (L1B) EV retrievals for the four LWIR PV bands [11]. The Aqua MODIS LWIR PV bands have been observed for many years to have anomalous features in the calibration coefficients derived from the BB calibration even though they are relatively smaller compared to those observed in the corresponding Terra MODIS bands [12,13]. We will clearly show, from the lunar imagery analysis, that non-negligible crosstalk effect exists among the four Aqua LWIR PV bands and that the crosstalk contamination level changes with time.
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