In this paper, we present the results obtained in the determination of the true north direction on Mars by using a gnomon on the InSight mission and compare the measurements with either the North determination from the Inertial Measurement Unit and imaging analysis. The obtained measurement has been used to populate the SEIS orientation information in the archived SEIS data. Images taken during December 2018 and January 2019 allow to determine the gnomon shadow position and length over a target. By calculating the Sun local coordinates using planetary ephemeris VSOP87, the images are used to estimate the true North direction on the landing site. By using eight different images selected, we obtain the true North direction with an accuracy up to 2.5°, which is confirmed by the IMU and imaging analysis. The true North direction is also confirmed by an image taken near local noon, when the sun crosses the meridian. The North determination precision is then discussed in view of the seismic determination of the back azimuth.

中文翻译：

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在火星上寻找SEIS北：日SE，惯性和影像测量与地震分析的结果之间的比较

在本文中，我们介绍了通过在InSight任务中使用gnomon在火星上确定真正的北向所获得的结果，并将测量结果与惯性测量单元的北向确定以及成像分析进行了比较。所获得的测量值已用于在归档的SEIS数据中填充SEIS方向信息。在2018年12月和2019年1月期间拍摄的图像可以确定目标上方的gnomon阴影位置和长度。通过使用行星星历表VSOP87计算太阳局部坐标，这些图像可用于估算着陆点的真实北向。通过选择八幅不同的图像，我们获得了高达2.5°的准确北向，这已通过IMU和成像分析得到了证实。当太阳穿过子午线时，也可以通过当地正午附近拍摄的图像来确定真正的北向。然后根据后方位角的地震确定讨论北确定精度。