Infrared Observations Of the Eclipsed Moon from Space


	The thermal profile for various regions of the Moon during the eclipse is shown above. Each data point for a given feature is the brightness temperature measured on an individual scan; the spacing graphically shows the time resolution of the data. The first data point for Mare Crisium is at a time just after it has entered the Earth’s shadow. All the other features are in the lunar western hemisphere and have been in shadow for 20 to 40 minutes. The data labeled SW Limb refers to a point about 10% of the radius from the limb at a position angle of about 80° in view graphs 9 and 10. This is not the coolest area but was chosen because it remains in shadow during the last DCE and data are available from all three DCEs.
	The 4.3 µm brightness temperatures are as much as 40K warmer that those derived from mid-IR maps. As an extreme example, Saari and Shorthill¹⁴ measured a 170K mid-IR brightness temperature for Mare Humorum, which is ~40K cooler than the 4.3 µm value above. The difference appears to be real as likely additional flux contributions from the out of band spectral response and the uncertainties in the effective solid angle, the dark offset and scattering correction are of the order of the 5% absolute calibration uncertainty. A 5% flux uncertainty corresponds to 1K in brightness temperature. The 4.3 µm flux has to change by a factor of two in order to decrease brightness temperature by 10K.
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	¹⁴Saari, J.M., R.W. Shorthill, 1965, Review of Lunar Infrared Observations, in Physics of the Moon: Science and Tech Ser., 13, Amer. Astronaut. Soc. (Pub, Tarzana CA).