Infrared Observations Of the Eclipsed Moon from Space

Introduction

•Space craft and infrared sensor

–MSX – multi-objective BMDO experiment

–SPIRIT II

•Line scanned radiometer

•The experiment

–3 observations of the 26 Sep 1996 lunar eclipse

•10 partial images of the Moon during each observation

•Results

–Numerous hot spots – seen previously in mid-IR

–Time and disk resolved cooling profiles


	The Midcourse Space Experiment (MSX) mapped the thermal 4.3 µm emission from the Moon during the 27 September 1996 eclipse at a resolution of about 30”. MSX obtained 4.3 µm brightness temperatures every 1 to 3 minutes during three observations of the eclipse and was thus able to define disk resolved (45km) cooling curves over the entire surface of the Moon. The temperature contrasts observed for various regions during eclipse agree well with those previously published, although there is a tendency for the MSX 4.3 µm values to be ~20K warmer. A large number of “hot spots” were observed, which correlate well with those noted by previous observers. Most of the warm discrete spots correspond to craters. The maria, and portions thereof, tend to be warmer than the highlands. This database on the details of the non-uniform cooling during the eclipse provide information on the thermo-physical properties of the various features on the surface of the Moon.
	The only previous published infrared maps of the entire Moon during eclipse at relatively high spatial resolution are those at 11 µm obtained by Shorthill² and by Saari et al.³ of the 19 December 1964 eclipse. They raster scanned a 10” beam across the Moon, taking ~16 minutes to complete a map. They noted hundreds of areas perceptively warmer than the surroundings, which they labeled as anomalies. They also found that the maria, or portions of maria, were warmer than the disk averaged temperature. Hunt et al.⁴ mapped about 70% of the Moon during the 13 April 1968 eclipse at 10 µm, looking for changes in the relative intensities of the anomalies between the epochs of the two eclipses, which they did not find. The MSX measurements are of lower spatial resolution, but the data are not aliased and each lunar observation is a snap-shot of only 10 seconds in duration.