DAT-CNN: Dual Attention Temporal CNN for Time-Resolving Sentinel-3 Vegetation Indices

Abstract

The synergies between Sentinel-3 (S3) and the forthcoming fluorescence explorer (FLEX) mission bring us the opportunity of using S3 vegetation indices (VI) as proxies of the solar-induced chlorophyll fluorescence (SIF) that will be captured by FLEX. However, the highly dynamic nature of SIF demands a very temporally accurate monitoring of S3 VIs to become reliable proxies. In this scenario, this article proposes a novel temporal reconstruction convolutional neural network (CNN), named dual attention temporal CNN (DAT-CNN), which has been specially designed for time-resolving S3 VIs using S2 and S3 multitemporal observations. In contrast to other existing techniques, DAT-CNN implements two different branches for processing and fusing S2 and S3 multimodal data, while further exploiting intersensor synergies. Besides, DAT-CNN also incorporates a new spatial–spectral and temporal attention module to suppress uninformative spatial–spectral features, while focusing on the most relevant temporal stamps for each particular prediction. The experimental comparison, including several temporal reconstruction methods and multiple operational Sentinel data products, demonstrates the competitive advantages of the proposed model with respect to the state of the art. The codes of this article will be available at https://github.com/ibanezfd/DATCNN.

Keywords

• Biophysical products
• fluorescence explorer (FLEX)
• Sentinel-2 (S2)
• Sentinel-3 (S3)
• temporal resolution