MW-Luna-2 – Establishing the Moon as reference for climate data from microwave sounders at low frequencies

简而言之，拟议项目的目的是确定对流层温度趋势的确定值，从而结束围绕各种微波卫星观测的争议。它的目的是通过建立一个具有不变表面的通量基准来实现这一点，所有微波探测仪在其运行寿命内都曾多次观测到这个基准：我们的月球。在一个前兆项目中，观测到的GHz频率的月球亮温与一个新模型的预测非常吻合。观测是用AMSU-B(先进微波探测仪B)和MHS(微波湿度探测仪)获得的。有了AMSU-A和ATMS(先进技术微波探测仪)，这项研究就有可能扩展到更低的频率，特别是54 GHz频段。已发表的基于这一波段的热带对流层温度的趋势在每十年0.09°到0.20°之间，这些不一致主要是由于仪器定标不完善造成的。相比之下，月球的亮温只取决于它与太阳的距离和视角。这种关系可以通过大量的观测得到非常准确的描述，这些观测发生在月球偶然出现的时候，也就是在常规操作期间，在微波探测仪的深空视野中。这项研究的重点是检测变化，并作为副产品获得月球辐射的绝对值。然而，它对未来的微波探测仪是有用的，特别是当内部校准源作为一种节省成本的措施被丢弃的时候。此外，仔细刻画不同日照条件下的月球盘面积分亮温，将有助于我们更好地了解月球表层的热物理性质。要分析的观测是使用AMSU-A在九颗不同的卫星上进行的，并在两颗卫星上使用自动取款机进行的。它们一起覆盖了满月周围约80°范围内的所有相位角。通常情况下，月球每年几次接近深空视野，然后连续出现在几个轨道上。由于大多数气象研究卫星的服役年限都在十年以上，每一颗卫星都有数百次月球观测，暴露了每一种可能的仪器异常，从而导致其校正和大气温度测量达到前所未有的精度。

In a nutshell, the aim of the proposed project is to set the definitive value for the trend in tropospheric temperature and thus to put an end to the controversies surrounding the various microwave satellite observations. It is the intention to achieve this by establishing a flux reference with an unchangeable surface that has been observed by all microwave sounders many times over their operational lifetime: our Moon. In a precursor project it was demonstrated that the observed lunar brightness temperatures at a frequency of 89 GHz are in very good agreement with the predictions of a new model. The observations were obtained with AMSU-B (Advanced Microwave Sounding Unit - B) and MHS (Microwave Humidity Sounder). With AMSU-A and ATMS (Advanced Technology Microwave Sounder) it is possible to extend this investigation to lower frequencies, in particular the 54 GHz band. Published trends of the tropical tropospheric temperature based on this band range from 0.09° to 0.20° per decade, and these inconsistencies arose mainly from imperfect instrument calibration. In contrast stands the brightness temperature of the Moon, which depends only on its distance from the Sun and the viewing angle. This relationship can be characterized very accurately with the great number of observations that happened, when the Moon appeared serendipitously, i. e. during routine operations, in the deep space view of a microwave sounder. The focus of this study is on detecting changes, and the absolute value for the radiance of the Moon is obtained as a by-product. It would nevertheless be useful for future microwave sounders, in particular when the internal calibration source is dropped as a cost saving measure. Besides, the careful characterization of the disk-integrated brightness temperature of the Moon under various conditions of solar illumination would improve our understanding of the thermo-physical properties of its regolith. The observations to be analyzed were made with AMSU-A on nine different satellites and ATMS on two satellites. Together they cover all phase angles within some 80° around full Moon. Usually the Moon approaches the deep space view several times per year and shows then up in several orbits in a row. As most of the meteorological research satellites are more than ten years in service, one gets hundreds of observations of the Moon from each of them, betraying every possible instrumental anomaly and thus leading to its correction and the measurement of atmospheric temperatures with unprecedented accuracy.