Abstract
The reflected light from the Moon can be utilized as a reference for radiometric calibration by employing a model to generate reference values corresponding to the Moon observations made by instruments. Using a calibration target that is outside the atmosphere provides a distinct advantage for space-based instruments; however, the lunar irradiance sensed by satellite instruments naturally changes as the host spacecraft traverses its orbit. This article presents a study of the potential impact on lunar radiometric measurements due to their acquisition from an orbiting platform. A simulation of a Sun-synchronous orbit was coupled to the U.S. Geological Survey (USGS) lunar model to generate predicted irradiances for points along orbit passes through several lunations. These irradiance values exhibit variations tied to the spacecraft motion, arising primarily from changes in the Moon-sensor distance and the phase angle. The two effects are similar in overall magnitude, but their respective contributions depend on the time of month and the orbit. Relative changes in irradiance mostly fall within an envelope of ±0.006% per second, except at the smallest phase angles. These studies enable planning space-based Moon observations to minimize the change in the target irradiance, an important consideration for measurements acquired for radiometric characterization of the Moon.
Highlights
T HE increasing recognition of the advantages of using the light from the Earth’s Moon as a radiometric reference has prompted further interest in improving lunar calibration techniques
Symbols were not plotted for times when the Moon’s elevation was below the 120 km viewing constraint, producing the vacant region seen within the positive phase angles for phases ∼18◦ and higher
The right panel of the figure expands a portion of the phase angles before Full Moon, allowing to discern the individual orbit passes as groups of adjacent data points
Summary
T HE increasing recognition of the advantages of using the light from the Earth’s Moon as a radiometric reference has prompted further interest in improving lunar calibration techniques. Lunar calibration has the potential to deliver climate-quality capabilities [1] for quantitative on-orbit evaluation of sensors at reflected solar wavelengths, ∼350 nm to 2500 nm, that can meet essential objectives for developing climate records from datasets produced by space-based Earth observing systems. With advanced development of the lunar radiometric reference, utilizing the Moon as a common target for intercalibration can be key to implementing a constellation approach for Earth environmental observing systems. Interconsistency of data products from the separate constellation components follows from calibrating the sensors to the same reference while on orbit, and the Moon provides a calibration target that is free from atmospheric interference. Lunar calibration can be leveraged for cross-calibration to benchmark reference instruments such as CLARREO (Climate Absolute Radiance and Refractivity Observatory [2]) and TRUTHS (Traceable Radiometry Underpinning Terrestrialand Helio-Studies [3], [4]).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: IEEE Transactions on Geoscience and Remote Sensing
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
