在多普勒和距离可观测量中火星旋转参数的特征
Signatures of the Martian rotation parameters in the Doppler and range observables
摘要：
火星着陆器的位置受到火星旋转运动的不同方面的影响：章动，岁差，日长变化和极移。这些不同的运动在地球和火星表面的着陆器之间的多普勒观测中有不同的签名。了解这些特征之间的相关性以及这些特征在一天或更长时间尺度内不为零的时刻对于确定最大化大地测量实验的地球物理观测回报的策略非常重要，特别是对于未来NASA InSight或ESA-Roscoplant ExoMars 2020任务的策略。我们提供了一阶公式的签名的旋转参数的多普勒和距离可观的。这些表达式是火星日自转、着陆器位置、行星半径和自转参数的函数。此外，在多普勒观测的章动签名是成比例的地球相对于火星的下降。对于靠近赤道的火星着陆器，多普勒观测到的最大特征的运动是由于日长变化，岁差率和刚性章动。极移和液核特征的振幅要小得多。对于一个更接近极点的着陆器，极地运动特征增强，而其他特征减少。我们还数值计算了其他行星或卫星上的着陆器在多普勒观测到的旋转参数签名的幅度。
英文摘要：
The position of a Martian lander is affected by different aspects of Mars' rotational motions: the nutations, the precession, the length-of-day variations and the polar motion. These various motions have a different signature in a Doppler observable between the Earth and a lander on Mars' surface. Knowing the correlations between these signatures and the moments when these signatures are not null during one day or on a longer timescale is important to identify strategies that maximize the geophysical return of observations with a geodesy experiment, in particular for the ones on-board the future NASA InSight or ESA-Roscosmos ExoMars2020 missions. We provide first-order formulations of the signature of the rotation parameters in the Doppler and range observables. These expressions are functions of the diurnal rotation of Mars, the lander position, the planet radius and the rotation parameter. Additionally, the nutation signature in the Doppler observable is proportional to the Earth declination with respect to Mars. For a lander on Mars close to the equator, the motions with the largest signature in the Doppler observable are due to the length-of-day variations, the precession rate and the rigid nutations. The polar motion and the liquid core signatures have a much smaller amplitude. For a lander closer to the pole, the polar motion signature is enhanced while the other signatures decrease. We also numerically evaluate the amplitudes of the rotation parameters signature in the Doppler observable for landers on other planets or moons.
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