Effects of Ellipsoidal Earth Model on Estimating the Sensitivity of Moon-Based Outgoing Longwave Radiation Measurements

The outgoing longwave radiation (OLR) at the top of the atmosphere is a key component of Earth’s radiation budget. Moon-based OLR observations take Earth as a single point, and provide an alternative to near-Earth orbital measurements. However, in the sensitivity design of a sensor, the effects of adopted Earth’s shape on the design of the sensitivity are particularly severe in the Moon-based OLR observations, which needs to be fully considered. In this study, the observational solid angle related to the ellipsoidal Earth model during OLR measurements was analyzed to improve upon previous studies conducted under the assumption of a spherical Earth. The radiative equilibrium temperature of the Earth–atmosphere system was then applied to simulate the emitted OLR according to Stephen Boltzmann’s law. The magnitude and sensitivity of the Moon-based OLR measurements were estimated by combining the observational solid angle and the simulated OLR. The results showed that the sensitivity of Moon-based OLR measurements is on the order of
$10^{-3}$
W m
⁻²
K
⁻¹
, and the effects of Earth’s shape on sensitivity estimates cannot be ignored. Further, quantitative estimates revealed that a more realistic (ellipsoid) shape is needed when designing the sensitivity of relevant sensors.