Background for CE-1 data research

Ken Tsang

Publications:Chan, K. L., K. T. Tsang, B. Kong, Y. C. Zheng, 2010. ‘Lunar regolith thermal behavior revealed by Chang'E-1 microwave brightness temperature data’. Earth and Planetary Science Letters. 295, 287-291.

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.

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, 26-27 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.

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

Major technical parameter of CE-1 MRM

Instrument CE-1 MRM

Frequencies 3.0, 7.8, 19.35 and 37 GHz

Integration time

200(±15%) ms

Temperature Sensivity

≤0.5 K

Linearity ≥0.99

Footprint56km for 3.0GHz and 30km for other three channels

MRM data at various level of preprocessing

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).

Channel 1

Channel 2

Channel 3

Channel 4

Sun Incidence Angle

Sun Azimuth Angle

Longitude

Latitude Distance

-119.7 213 198.43 198123.35

7164.165

480.5211 -54.045

199.9377

-119.58 212.84 198.5 198.11123.28

5164.179

880.5201 -54.120

199.9333

-119.68 213.15 198.58 198.17123.21

3164.194

280.519 -54.195 199.929

-118.46 213.49 198.96 198.47123.05

1164.226

480.5166 -54.364

199.9192

-119.19 213.63 198.93 198.53122.97

8164.240

880.5155 -54.440

199.9146

-119.21 213.77 198.94 198.59122.90

6164.255 80.5144 -54.515

199.9103

-119.3 213.74 199 198.64122.83

4164.269

180.5133 -54.590

199.9059

-119.59 213.66 199.06 198.6122.76

2164.283

380.5123 -54.665

199.9014

-119.69 213.69 199.08 198.57122.68

9164.297

480.5112 -54.740

199.8971

MRM data stored in SQL-server

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Some details of the Earth-Moon system

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 (0.02 - 0.04W·m-2 ) and

•Radiation from lunar surface.

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, 102-135, 1930

• Topographic effects (sloping surfaces, craters)

• Soil physics: emissivity, dielectric properties

CE-1 Data Preprocess Horizontal coordinate

system:

A: Azimuth & a: altitude

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 Su

n

Transformation of Horizontal to Equatorial Coordinates

A: Azimuth

a: altitude

: Hour Angle

: Declination (偏差 )

: Lunar Latitude

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

CE-1’s 37GHz TB data

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.

Raw data: latitude between ±1°

Hour Angle

TB

Data

After removing the noise: latitude between ±1°

Hour angle

TB

Regression with degree-seven polynomial

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

Hour angle

TB

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

Lati

tud

e

The figure below is the data visualization method for the the actual data points.

EDA analysis for a small region

Spatial interpolation

Linear interpolation

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

A

BC

Nonlinear Interpolation• Common types:

1. Inverse Distance Weighted 2. Kriging

TB map without local time treatment

TB map without local time treatment

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

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

TiO2 distribution retrieved from Clementine UV-VIS-IR data (Lucey et al., 2000)

Correlation studies

Lucey, P. G., et al., 2000. Lunar iron and titanium abundance algorithms based on final processing of Clementine ultraviolet-visible images. Journal of Geophysical Research-Planets. 105, 20297-20305.

40

Correlation between 37GHz daytime TB and TiO2 at equator

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.

Conditional Correlation

Lunar regions with TiO2

content higher than 0, 3, 6, and 9 wt.%

(top to bottom)

37GHz

3GHz3GHz

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 angle2. 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.

Thank you!

Voronoi Domain