Infrared Observations Of the Eclipsed Moon from Space


	The discrepancy between mid- and near infrared observations could be brought into accord if the 4.3 µm emissivity of the Moon was ~65% higher than that in the mid-infrared. This is, of course, at odds with the usual assumption that the Moon is grey with an emissivity of 0.9. However, Murcray et al¹¹ measured a wavelength dependent emissivity between 7 – 13.5 µm fpr six regions of the nearly full during a balloon flight on 13 April 1868. Vogler et al.¹² corrected the Murcray et al. results for the residual atmospheric absorption above the balloon and found that the normalized emissivity varied from 90% at 13.5 µm to 105% at 7 µm. Murcray¹³ also observed a 30° latitudinal strip of the full Moon in September and October 1964 in three spectral bands between 8.4 and 11 µm and determined that the energy distribution was wider than a single temperature blackbody. Vogler et al.¹² inferred from these results that the partial disk integrated brightness temperature of the full Moon has a mid-infrared slope of – 3K/µm. While it is perilous to extrapolate these observations by a factor of two in wavelength and then to apply the results to the eclipsed Moon, the observed trend is in the correct sense to account for the 4.3 µm brightness temperature measurements.
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	¹¹Murcray, F.H., D.G. Murcray and W.J. Williams 1970. Infrared emissivities of lunar surface features. Balloon observations, J. Geophys. Res. 75, 2662 –2669.
	¹²Vogler, K.J., P.E. Johnson and R.W. Shorthill 1991, Modeling the Non-Grey-Body Thermal Emission From the Full Moon. Icarus 92, 80 – 93.
	¹³Murcray, F.H., 1965, The spectral dependence of lunar emissivity, J. Geophys. Res. 70, 4959 – 4962.