Internet of Things (IoT) is an important infrastructure for supporting vertical applications. However, existing IoT systems are still facing some challenges, e.g., lack of coverage in rural areas and lack of efficient data collection methods. To overcome these challenges, a satellite IoT framework is proposed in this study as a promising solution, and smart agriculture is used as a typical application scenario. A satellite edge computing workflow is further proposed, with computer vision as a case study. In the case study, a lightweight deep learning model named MobileViT is proven effective for aphid detection and infestation severity classification on lemon leaves.