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Background for CE-1 data research Ken Tsang

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Publications: Chan, K. L., K. T. Tsang, B. Kong, Y. C. Zheng, ‘Lunar regolith thermal behavior revealed by Chang'E-1 microwave brightness temperature data’. Earth and Planetary Science Letters. 295, Y. C. Zheng, K. T. Tsang, K. L. Chan, Y. L. Zou, F. Zhang, and Z. Y. Ouyang, ‘First Microwave Map of the Moon with Chang’E-1 data: the Role of Local Time in Global Imaging’, Icarus, 2012.

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Meetings: K. T. Tsang, Y. C. Zheng, K. L. Chan, F. Zhang, Y. Zou, and Z. Ouyang, “Correlation Studies of CHANG'E-1 Lunar Microwave Image and Clementine Data”, Paper PS10-A012, Asia Oceania Geosciences Society Annual Meeting, 8 Aug 2011, Taipei. K. T. Tsang, Y. C. Zheng, K. L. Chana, X. Y. Lic, Q. X. Lid, D. Zhang, Y. Liao, “Seasonal temperature variation in the polar regions of the Moon”, International Symposium Lunar Planetary Science, March 2012, Macau. K. T. Tsang, “Correlation Studies of CHANG'E-1 Lunar Microwave Image and Clementine Data”, 31 August 2011, seminar given at Applied Physics Laboratory, Johns Hopkins University.

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Artist’s view of MRM on-board Chang’E-1

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Major technical parameter of CE-1 MRM InstrumentCE-1 MRM Frequencies3.0, 7.8, and 37 GHz Integration time 200(±15%) ms Temperature Sensivity ≤0.5 K Linearity≥0.99 Footprint 56km for 3.0GHz and 30km for other three channels

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MRM data at various level of preprocessing

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Chang’E-1 microwave brightness temperature data preprocessed to a distributable PDS (Planetary Data System) format. relevant info in each record are: –the UTC time of the measurement, –brightness temperature from the 4 microwave channels, –solar incident angle, –solar azimuth angle, and –the orbital information of CE-1 (longitude, latitude and orbital altitude).

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Channel 1Channel 2Channel 3Channel 4 Sun Incidence Angle Sun Azimuth Angle LongitudeLatitudeDistance

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MRM data stored in SQL-server

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Some details of the Earth-Moon system

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Factors that determine the Lunar surface temperature Ignoring topographical effects, seasonal and diurnal temperature variation in the surface lunar layers are determined by the balance between Solar radiation (1366W·m -2 ) Earthshine (0.099~0.201 W·m -2 ) Internal heat flow ( W·m -2 ) and Radiation from lunar surface.

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Dependence of lunar surface temperature No seasonal variation (except at the poles) Diurnal variation (hour angle) Lunar latitude –Lambertian model –Pettit and Nicholson, “Lunar radiation and temperatures”, Astrophys. J., 71, , 1930 Topographic effects (sloping surfaces, craters) Soil physics: emissivity, dielectric properties

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CE-1 Data Preprocess Horizontal coordinate system: A: Azimuth & a: altitude

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The main disadvantage of the horizon system is the steady change of coordinates for a given astronomical object as Moon rotates. This can be removed by using a coordinate system which is fixed at the stars (or the celestial sphere defined with the Moon). We define the lunar equatorial coordinate system similar to that defined for Earth and thus convenient for lunar observers. Data Preprocess: The Lunar Equatorial Coordinate system

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The Horizontal System and the Equatorial Coordinate system Sun

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Transformation of Horizontal to Equatorial Coordinates A: Azimuth a: altitude : Hour Angle : Declination ( 偏差 ) : Lunar Latitude

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Hour angle is the angular displacement of the sun east or west of the local meridian due to rotation of the moon on its axis at 15° per lunar hour with morning being negative and afternoon being positive. Hour Angle

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The Lunar Thermal Environment

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CE-1’s 37GHz TB data

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Analyze the 3-Dimensional data of CE-1 (TB depends on Latitude, Longitude, Hour-angle) Exploratory data analysis (EDA) Exploratory data analysis (EDA) is an approach to analyze data for the purpose of formulating hypotheses worth testing, complementing the tools of conventional statistics for testing its basic characteristic. The principle graph techniques used in EDA are scalar plot, histogram plot and other tools.

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Raw data: latitude between ±1° Hour Angle TB Data

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After removing the noise: latitude between ±1° Hour angle TB

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Regression with degree-seven polynomial

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Regression analysis in Hour-angle for 3 different latitude TB data within narrow latitude bands extending ±1°up & down Hour angle TB

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First, we could see the raw data below, which is regular, but there has some repetitive cover data (at fixed HA) EDA analysis for a small region Longitude Latitude

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The figure below is the data visualization method for the the actual data points. EDA analysis for a small region

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Spatial interpolation

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Linear interpolation Half way from A to B, Value is (A + B) / 2 A B C

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Nonlinear Interpolation Common types: 1. Inverse Distance Weighted 2. Kriging

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TB map without local time treatment

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Major hot regions on the Moon (37GHz TB image)

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TiO2 distribution retrieved from Clementine UV- VIS-IR data (Lucey et al., 2000) Correlation studies Lucey, P. G., et al., Lunar iron and titanium abundance algorithms based on final processing of Clementine ultraviolet-visible images. Journal of Geophysical Research-Planets. 105,

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40 Correlation between 37GHz daytime TB and TiO2 at equator

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However, if the correlation is computed for the whole moon, the correlation is very low. This may be due to noises on the maps, missing data, or the influence of shadows.

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Conditional Correlation

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Lunar regions with TiO2 content higher than 0, 3, 6, and 9 wt.% (top to bottom)

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37GHz 3GHz

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Conclusion 1.For global imaging, it is important to distinguish between the spatial and local time effects on the CE-1 MRM data. 2.We introduce the solar “hour angle” as a local time variable. 3.TB is a function of latitude, longitude, and hour angle. 4.Imaging procedure: 1.regression analysis on hour angle 2.Spatial interpolation 5.Correlation studies with CE-1 MRM data and Clementine UV-VIS-IR data 6.High TiO2 content may be responsible for some interesting day-night thermal behavior in Oceanus Procellarum and Mare Tranquillitatis.

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Thank you!

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Voronoi Domain

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