Evaluation of air-LUSI Measurements to Advance Lunar Modeling and the ROLO Lunar Calibration Reference

Date

2021-10-20

Department

Program

Citation of Original Publication

Rights

This item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.
Public Domain Mark 1.0
This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.

Subjects

Abstract

The airborne Lunar Spectral Irradiance (air-LUSI) project is dedicated to acquiring high-accuracy, spectrally resolved measurements of the Moon from the NASA ER-2 high-altitude aircraft, flying above more than 90% of Earth's atmosphere. The air-LUSI instrument is a non-imaging system designed specifically for measuring spectral irradiance of the Moon at wavelengths from ~350 nm to 1100 nm. The project aims to achieve absolute measurement uncertainty approaching 0.5% (k=1) with traceability to NIST radiometric standards and SI. These measurements can advance lunar calibration by constraining absolute scale of models that constitute the lunar radiometric reference, such as the USGS ROLO model. A 5-night flight campaign in November 2019 collected lunar measurements at phase angles ranging from 9.4 to 58.5 degrees after Full Moon. ROLO model outputs have been generated for the times and aircraft locations of each night's observations. Inter-night comparisons after normalizing by ROLO show inter-consistency of the measurements within 1.5%, despite a factor of 3.34 difference in lunar irradiance at 500 nm over the 5-night span. These results give no indication of an appreciable phase angle dependence in the ROLO model within the observed range. This talk will highlight implications of the high-accuracy air-LUSI measurements with regard to lunar calibration using irradiance measurements derived from lunar images acquired by space-based sensors.