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Background for CE-1 data research

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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.

- 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).

MRM data stored in SQL-server

Some details of the Earth-Moon system

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.

- 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

Data Preprocess: The Lunar Equatorial Coordinate system

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.

The Horizontal System and the Equatorial Coordinate system

Sun

Transformation of Horizontal to Equatorial Coordinates

A: Azimuth

a: altitude

: Hour Angle

: Declination (偏差)

: Lunar Latitude

Hour Angle

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.

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°

TB Data

Hour Angle

After removing the noise: latitude between ±1°

TB

Hour angle

Regression with degree-seven polynomial

Regression analysis in Hour-angle

for 3 different latitude TB data within narrow latitude bands extending ±1°up & down

TB

Hour angle

EDA analysis for a small region

First, we could see the raw data below, which is regular, but there has some repetitive cover data (at fixed HA)

Latitude

Longitude

EDA analysis for a small region

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

C

B

Half way from A to B,

Value is (A + B) / 2

A

- 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)

Correlation studies

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

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.

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.

Lunar regions with TiO2 content higher than 0, 3, 6, and 9 wt.%

(top to bottom)

37GHz

3GHz

3GHz

- For global imaging, it is important to distinguish between the spatial and local time effects on the CE-1 MRM data.
- We introduce the solar “hour angle” as a local time variable.
- TB is a function of latitude, longitude, and hour angle.
- Imaging procedure:
- regression analysis on hour angle
- Spatial interpolation

- Correlation studies with CE-1 MRM data and Clementine UV-VIS-IR data
- High TiO2 content may be responsible for some interesting day-night thermal behavior in Oceanus Procellarum and Mare Tranquillitatis.

Voronoi Domain