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Studies were conducted to define lunar radiances on an absolute radiometric scale tied to the International Temperature Scale of 1990 (ITS-90). The Clouds and the Earth's Radiant Energy System (CERES) thermistor bolometer sensor instruments were used to measure lunar radiances from the NASA Tropical Rainfall Measuring Mission (TRMM), Terra, and Aqua spacecraft platforms. Each CERES instrument package consisted of three different sensors: (1) broadband shortwave [0.3 to 5 micrometers]; (2) broadband total [0.3 to >100 micrometers]; and (3) narrowband, water vapor window [8 to 12 micrometers]. Moon-reflected solar radiances were measured with the shortwave sensor while both moon-reflected solar and moon-emitted longwave radiances were measured using the total sensor. The differences between the total and shortwave sensor measurements were used to determine the broadband longwave, moon-emitted radiances. The narrowband, water vapor window sensor measured only the longwave, moon-emitted radiances. The radiances were obtained as a function of phase angle (formed at the moon between directions to the sun and the spacecraft). The resulting filtered radiances were normalized to the mean sun-moon distance, one astronomical unit (AU), and to the mean earth-moon distance of 0.0026 AU (384,400 kilometers). 1998, 2000, and 2001, CERES lunar filtered measurements are presented, compared, and analyzed. Additional measurements are presented from the January 9, 2001, and May 16, 2003, total lunar eclipse events. Analyses of the Clouds and the Earth's Radiant Energy System (CERES) thermistor bolometer sensor observations of lunar radiances indicated that broadband shortwave and longwave lunar filtered radiances can be linked to a radiometric scale based upon an International Temperature Scale of 1990 (ITS-90) at absolute levels approaching ± 0.2 Wm-2sr-1. For a lunar image diameter of 31 minutes of arc, an emitting lunar disc temperature of approximately 400 Kelvin was estimated from the longwave radiances near 7-degree phase angle. The integration of the CERES unfiltered radiances over all reflection angles can be used to define the moon radiation budget (MRB).
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