remote sensing Article Entrance Pupil Irradiance Estimating Model for a Moon-Based Earth Radiation Observatory Instrument Wentao Duan 1, Shaopeng Huang 2,3,* and Chenwei Nie 4 1 School of Human Settlements and Civil Engineering, Xi’an Jiaotong University, Xi’an 710054, China;
[email protected] 2 Institute of Deep Earth Science and Green Energy, Shenzhen University, Shenzhen 518060, China 3 Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109, USA 4 Key Laboratory of Digital Earth Science, Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100094, China;
[email protected] * Correspondence:
[email protected] Received: 26 January 2019; Accepted: 6 March 2019; Published: 10 March 2019 Abstract: A Moon-based Earth radiation observatory (MERO) could provide a longer-term continuous measurement of radiation exiting the Earth system compared to current satellite-based observatories. In order to parameterize the detector for such a newly-proposed MERO, the evaluation of the instrument’s entrance pupil irradiance (EPI) is of great importance. The motivation of this work is to build an EPI estimating model for a simplified single-pixel MERO instrument. The rationale of this model is to sum the contributions of every location in the MERO-viewed region on the Earth’s top of atmosphere (TOA) to the MERO sensor’s EPI, taking into account the anisotropy in the longwave radiance at the Earth TOA. Such anisotropy could be characterized by the TOA anisotropic factors, which can be derived from the Clouds and the Earth’s Radiant Energy System (CERES) angular distribution models (ADMs).