An Improved Rock Method for the Chang’E-2 Microwave Radiometer Datasets

Le résumé fourni par la source

Chang’E (CE) microwave radiometer (MRM) measurements provide a unique opportunity to detect the heat flow (temperature gradients) across the global Moon. However, rocks influence the brightness temperature (TB) and consequently impact the precision of the inferred temperature gradients derived from the antenna temperature (TA) sensed by the CE MRM. Hence, we propose an improved rock method to simulate the TA using assumed antenna patterns corresponding to the main beam width and efficiency as specified by the MRM manufacturer. In order to quantify the rock effect, the CE MRM’s footprint is segmented into square grids matching the Diviner’s footprint resolution (128 pixels per degree). The rock abundance (RA) derived from Diviner infrared measurements is used to determine the antenna weight for each discrete cell within the MRM footprint. The cumulative weight for rocks is then obtained by summing the weights of all rock-containing cells. Conversely, the weights without rocks are calculated by subtracting the rock weights from one. For the TB of both the regolith and rocks within each cell, we compute these values based on our established TB and thermal heat models. Subsequently, we utilize the highland diurnal TAs observed at the same latitudes with a 0.01° bandwidth to estimate the loss tangent outside the crater. The diurnal agreements between the simulated and observed TAs over four selected fresh craters demonstrate that our method works well and the rock effect was slightly exaggerated in our earlier rock model. Furthermore, based on our validated model, the estimated average diurnal TB difference induced by rocks between the 10 cm (3 GHz) and 3.85 cm (7.8 GHz) channels is approximately 0.33 K. This magnitude suggests that the rock effect should be accounted for in future MRM-based heat flow retrievals, particularly over rocky terrains like fresh craters.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.