Probing Atmospheric Properties of Mars and Venus by High-Resolution Infrared Heterodyne Spectroscopy of CO2

了解行星大气的物理和化学过程对发展大气环流模式和气象预报模式至关重要。这不仅适用于地球，也适用于其他类地行星，如火星和金星。特别是在火星的情况下，大气模型在过去几年中已经得到了很大的改进，这是由于几个太空任务（如火星新闻、火星全球勘测者（MGS）和火星漫游者）提供的数据所施加的限制。然而，这些数据只是选择性的，主要来自火星表面和有限的海拔区域。在其他（较高）大气区域的观测很少，但对于约束模型和为未来的太空任务和登陆器做准备是必要的。其中一个预报参数是纬向风速。与地球上的急流类似，预计火星上的全球纬向气流在80公里高度附近风速可达200米/秒。利用高光谱分辨率外差光谱法观测红外CO2吸收和发射线是测量高大气风的一种简便方法。从线频（多普勒-）可以直接推导出发射气体和吸收气体的频移速度。与微波观测相比，红外外差观测技术除了具有较高的光谱分辨率外，还可以获得足够的空间分辨率。类似的观测也计划在金星上进行，以支持欧洲航天局的金星快车太空任务。

Understanding of the physical and chemical processes in planetary atmospheres is essential for the development of general circulation models (GCM) and meteorological forecast models. This is not only true for Earth but for the other terrestrial planets, Mars and Venus, as well. Especially in the case of Mars, atmospheric models have been improved substantially over the last few years due to constraints imposed by the data that became available from several space missions e.g. MarsExpress or Mars Global Surveyor (MGS) and the Mars Rovers. Nevertheless these data are only selective and mainly from the surface and from limited altitude regions of Mars. Observations in other (higher) atmospheric regions are rare but are necessary to constrain the models and to prepare for future space missions and landers to the Red Planet. One forecast parameter is zonal wind velocity. Similar to jet streams on Earth global zonal flows are predicted for Mars with wind velocities up to 200 m/s near 80 km altitude. An elegant method to measure high atmospheric winds is by observing infrared CO2 absorption and emission lines with high spectral resolution heterodyne spectroscopy. From line frequency (Doppler-)shifts velocities of the emitting and absorbing gas can be directly deduced. In contrast to microwave observations an adequate spatial resolution can be achieved in addition to the high spectral resolution with the infrared heterodyne observing technique. Similar observations are planned on Venus in the support of the ESA VenusExpress space mission.