Global Measurements of the Mars Upper Atmosphere: In Situ Accelerometer Measurements from Mars Odyssey 2001 and Mars Global Surveyor
Global Measurements of the Mars Upper Atmosphere: In Situ Accelerometer Measurements from Mars Odyssey 2001 and Mars Global Surveyor
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发表时间：
2003-03
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通讯作者：
G. Keating;M. Theriot;R. Tolson;S. Bougher;F. Forget;J. Forbes
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作者：
G. Keating;M. Theriot;R. Tolson;S. Bougher;F. Forget;J. Forbes
随着最近的火星奥德赛2001年加速计实验对高层大气的测量，现场测量终于从一个极点扩展到另一个极点。2001年9月，火星奥德赛2001号（M01）航天器被送入绕火星的近极地轨道。从那时起至2002年1月进行了空气制动，以使M01轨道成圆形。该航天器携带了三轴加速计，用于安全地进行空气制动，并继续探索高层大气的详细特性，这是从火星全球勘测者加速计测量开始的。加速度计用于测量大气密度，并根据在入境和出境轨迹上测量的垂直结构确定刻度高度、温度和压力。总共获得了600个垂直结构，范围从95公里到170公里以上。第一次在北极附近获得测量结果，也是第一次在北方半球的夜侧获得测量结果。随着冬季北极附近纬度最大化，发现110公里附近的温度意外升高，显然是由于动态加热[1]。这一结果与用于奥德赛大气制动的MarsGram和MTGCM模型相反，其中模型温度预测在冬季极点附近最小化。例如，在100公里处的北冬极附近观测到的最高温度接近200 K，而MTGCM温度预计接近100 K。然而，欧洲火星GCM [2]预测北极和南极在高海拔地区的冬季都会出现冬季极地变暖。北极附近气温的高度变化和高纬日变化也与Forget等人的模式基本雅阁。北半球冬季高层大气变暖可能是南半球夏季越赤道纬向环流下沉分支的绝热加热所致。南半球冬季极地高层大气温度的唯一测量值是从火星全球勘测者号上的加速度计获得的。这些测量结果没有显示冬季极地变暖，但冬季南极附近的最低温度更雅阁辐射平衡，更雅阁MTGCM模式。在近日点附近，向北冬极提供动力加热的夏冬环流明显强于向远日点附近南冬极提供动力加热的夏冬环流。较强的动力加热过程中...
With the recent Mars Odyssey 2001 Accelerometer Experiment measurements of the upper atmosphere, insitu measurements have finally been extended from pole to pole. The Mars Odyssey 2001 (M01) Spacecraft was placed into a near polar orbit about Mars in September 2001. Aerobraking was performed from then until January 2002 to circularize the M01 orbit. The spacecraft carried triaxial accelerometers, which were used to safely perform aerobraking and to continue exploration of the detailed properties of the upper atmosphere, which had begun with the Mars Global Surveyor accelerometer measurements. The accelerometers were used to measure atmospheric density, and from the vertical structures measured on both inbound and outbound trajectories the scale height, temperature and pressure were determined. Altogether 600 vertical structures were obtained ranging from 95 km to above 170 km. Measurements were obtained for the first time near the North Pole and also the first measurements were obtained on the night-side in the Northern Hemisphere. Temperatures near 110 km were discovered to unexpectedly increase with latitude maximizing near the North winter pole, apparently due to dynamical heating [1]. This result is contrary to the MarsGram and MTGCM models used for Odyssey aerobraking, where model temperatures are predicted to minimize near the winter pole. For example, maximum temperatures near the North winter pole at 100 km were observed to be near 200 K while MTGCM temperatures were predicted to be near 100 K. However, a winter polar warming is predicted by the European Mars GCM [2] at both the North and South Poles in local winter at high altitudes. The altitudinal variations and high latitude diurnal variations of temperature near the North Pole also appear to be in fair accord with the Forget et al. model. Apparently the upper atmosphere North polar winter warmings may result from adiabatic heating from the subsiding branch of the cross-equatorial meridional circulation from the Southern Hemisphere summer. The only measurements of the Southern Hemisphere winter polar upper atmospheric temperatures were obtained from accelerometers aboard the Mars Global Surveyor. These measurements do not show winter polar warmings, but minimum temperatures near the winter South Pole more in accord with radiative equilibrium, and more in accord with the MTGCM model. Apparently the summer-to-winter cell supplying dynamical heating to the North winter pole near perihelion is much stronger than the summer-to-winter cell supplying dynamical heating to the South winter pole near aphelion. The stronger dynamical heating during the …