| Abstract: |
I. INTRODUCTION
Physical temperature of Moon surface has been well studied by the thermal conduction equation with lunar geographic, topographic and physical properties of lunar meia. Multi-channel microwave radiometers upload on Chinese Chang’E-1 and -2 (CE-1 and -2) satellites had measured the brightness temperature (Tb) of full Moon surfaces, and physical temperature and regolith layer thickness of lunar surface were inverted, and the 3He abundance was evaluated [1-3].
In December 2016, as second generation of Chinese geosynchronous meteorological satellite, the Feng Yun-4 (FY-4) was launched. Its high quality data have been well distributed to meteorological sevices. Muli-channel milimeter waves (180-450 GHz) are planed to be upload on the No. 3 of FY-4 series.
Based on inversion of physical temperature of the lunar surface, calibration for microwave sensors on Chinese geosynchronous satellite, FY-4, is proposed. This paper is to study the inversion of physical temperature of lunar surface based on one-dimentional thermal conduction equation, validated by analysis of Chang’E-1 and -2 data, and present the feasibility for FY-4 calibration.
II. PHYSICALTEMPERATURE OF MOON SURFACE
Based on one-dimensional (1-D) thermal conduction equation with boundary conditions, physical temperature of lunar regolith media can be derived. It is related with solar radiance, and other lunar geographic, topographic and physical parameters.
Fig. 1 shows a typical result to describe the diurnal variation of physical temperature of lunar surface.
III. INVERSION OF PHYSICAL TEMPERATURE FROM CE-1 DATA
It is the first time to make microwave measurement of thermal emission of full lunar surface by CE-1 and -2 [1]. Inversions of physical temperature, regolith layer thickness and abundance of 3He have been studied.
Furthermore, fused with the measurements of the Diviner Lunar IR Radiometer and the subsurface thermal properties from the Apollo Heat flow probes, we create a forward model to predict multi-channel Tb from lunar regolith media in the microwave spectrum. These models can then be directly compared and matched to data from multi-channel microwave radiometers flown aboard the CE-1 and -2 missions [2]. The effective complex dielectric constant of the lunar regolith as a function of depth at different frequency channels is derived.
Fig. 4 shows physical temperature at different lunar local time inverted from CE-1 Tb37 data at the Sinus Iridum area, where CE-3 landed. It shows diurnal variation. Inversions of CE-1 and -2 Tb data are well compared with analysis of solving 1-D thermal conduction equation [3].
Figs. 2-5 show some results of thi sstudy.
IV. CALIBARATION FOR FY-4 MILIMETER SENSORS
Based on solar emisssion, distance between Sun and Moon, and local parameters, as well as available, physical temperature of lunar surface can be accurately derived. Especially, high physical temperature at lunar equator at noon time keeps almost constant and can be well inverted. The surface emissivity to take account of local physical topography in the resolution can be numerically derived.
Thus, a proposal is presented to employ high temperatue of lunar equator at noon time, which is well derived and keeps almost constant for calibration of FY-4. As required by FY-4 technology, all related parameters are specifically designed in detail. The diagram of FY-4 calibration is shown in Fig. 6.
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