Thermal removal from near-infrared imaging spectroscopy data of the Moon

Abstract

[1] In the near-infrared from about 2 mm to beyond 3 mm, the light from the Moon is a combination of reflected sunlight and emitted thermal emission. There are multiple complexities in separating the two signals, including knowledge of the local solar incidence angle due to topography, phase angle dependencies, emissivity, and instrument calibration. Thermal emission adds to apparent reflectance, and because the emission's contribution increases over the reflected sunlight with increasing wavelength, absorption bands in the lunar reflectance spectra can be modified. In particular, the shape of the 2 mm pyroxene band can be distorted by thermal emission, changing spectrally determined pyroxene composition and abundance. Because of the thermal emission contribution, water and hydroxyl absorptions are reduced in strength, lowering apparent abundances. It is important to quantify and remove the thermal emission for these reasons. We developed a method for deriving the temperature and emissivity from spectra of the lunar surface and removing the thermal emission in the near infrared. The method is fast enough that it can be applied to imaging spectroscopy data on the Moon.

Interpretation of combined infrared, submillimeter, and millimeter thermal flux data obtained during the Rosetta fly-by of Asteroid (21) Lutetia

“…Consequently, inference of surface temperature from IR spectra is not possible without imposing some a priori constraints on the expected values of solution. A variety of approaches have been adopted in the past to cope with this condition (e.g., Clark, 1979;Clark et al, 2011). In most cases, the emissivity and the surface temperature are not retrieved simultaneously.…”

A visible and near-infrared photometric correction for Moon Mineralogy Mapper (M3)

“…Beyond 2 lm, the spectrum of the Moon is composed of light reflected from the surface plus thermal emission. The thermal emission is removed using the algorithm developed by Clark et al (2011) for the M 3 observations. The improved calibration and the thermal correction are used prior to defining an accurate photometric correction for all M 3 observations.…”

Lunar cryptomaria: Mineralogy and composition of ancient volcanic deposits

“…All of the VNIR spectra used in this study were collected from the Moon Mineralogy Mapper (M 3 ) dataset Clark et al, 2011;Green et al, 2011;Besse et al, 2013). M 3 was a VNIR imaging spectrometer aboard the Chandrayaan-1 spacecraft that collected mineralogic information about the Moon's surface in 85 bands, from approximately 0.4-3.0 μm, at a spatial resolution of 140-280 m/pixel, depending on the spacecraft altitude (Pieters et al, 2009;Green et al, 2011).…”