Characteristics Analysis of Earth’s Reflected Radiation Viewed From a Moon-Based Platform

The Earth’s outgoing radiation (EOR) at the top of atmosphere (TOA) is an advantageous goal of Moon-based Earth observations. In this study, we focused on the Earth’s reflected radiation (ERR), which is a component of EOR and has a strong relationship with the Earth–Moon–Sun positions. To determine ERR characteristics, we parameterized the Moon-based Earth observation geometry and proposed a method to simulate the ERR at TOA for a Moon-based sensor under clear- and all-sky conditions. The ERR was found to have the distinct cycle of a synodic month and was inversely proportional to the Earth’s phase angle. Clouds increased ERR reflected to space under hemispheric-scale observation; thus, ERR under all-sky conditions was approximately twice as much as that under clear-sky conditions. The ERR was also influenced by incoming solar radiation (ISR), and the removal of the effect of ISR on ERR helped reveal ERR characteristics clearly. The results showed that when the Earth’s phase angle was between 0° and 90°, particularly when the Earth’s phase angle was in the range of 30°–60° and 60°–90° under all- and clear-sky conditions, respectively, the ERR–ISR ratio could indicate the reflective characteristics of the Earth under hemisphere-scale observations. These results will be helpful in demonstrating Moon-based ERR monitoring.