摘要：The ocean has provided an important means of commerce and transport for centuries and does so to this day. With the ocean covering roughly 70% of Earth’s surface, much maritime activity occurs well out of sight of land. In addition to legitimate ocean activities, there may also be undesirable ones, such as dumping of pollutants, illegal fishing, drug and human trafficking, pirating, and perhaps even terrorism-related activities. Satellites provide a robust platform for observing shipping activities beyond shore-based sensors. Today’s commercially available satellite imagery offers a variety of data types and imaging opportunities. Electro-optical systems can provide quality imagery but are useless at night or when clouds are present. Synthetic aperture radar systems offer all-weather and day/night collection opportunities, and their importance has grown in recent years. These systems are promising tools for aiding those responsible for monitoring the environment, managing ecosystems, and enforcing the law.
