Innovative calibration methods for strapdown airborne vector gravimetry aboard HALO

捷联式机载矢量重力测量（SAVG）是利用捷联惯性测量单元（IMU）在飞机上测量三维地球重力场的一种方法。传统的稳定平台弹簧重力仪是航空重力测量的主要仪器，与之相比，SAVG具有以下优势：捷联式imu在尺寸、重量、功耗和成本方面节省了大量成本。此外，飞机上不需要操作员。- SAVG能够确定垂直方向的偏转（矢量重力测量）。-最近SAVG活动的结果表明，SAVG在对抗湍流和演习期间可以更加稳健。Universität达姆施塔特技术研究所（TUDa）的物理和卫星大地测量学小组建议参与该项目范围内的ANTHALO-BI活动（参见单独的任务提案），提供仪器和现场操作员。对于SAVG部分，ANTHALO- bi活动可以被视为更大的ANTHALO南极洲活动（计划于2020/21年进行）的科学可行性研究。对于这两个战役，TUDa的SAVG实验将贡献以下内容：- 1mgal级别的标量重力测量（水平：0.5 mGal），-垂直偏转（DoV），目标是0.5角秒精度，以及-高精度，高速率姿态和航向输出（预期精度分别为3和20角秒）。SAVG的一个关键部分是对惯性传感器误差的适当建模。TUDa最近的工作表明，离线IMU校准方法可以显着提高SAVG的整体性能，在最近的SAVG活动中产生1.0-1.4 mGal的标量重力（应用交叉调整后为0.5-0.6 mGal）。这是一项出色的性能，达到了经典弹簧重力仪的精度水平。鉴于ANTHALO- bi和ANTHALO运动，SAVG面临的一个特别挑战是远距离惯性传感器的稳定性。因此，本项目的主要目标是设计和评估针对远程SAVG量身定制的新型校准技术，旨在实现更高的长期稳定性，以及在机动和强湍流等动态情况下更大的鲁棒性。为此，将考虑扩展参数误差模型，包括偏差，比例因子和传感器交叉耦合，每一个都是传感器温度的函数，以及基于样本的（非参数）误差模型。为了进行评估，除了ANTHALO-BI简捷数据集外，还将使用现有的SAVG数据集，这些数据集将提供给TUDa。这项基础研究有望成为未来将捷联式航空重力测量作为航空重力测量默认方法的一步。

Strapdown airborne vector gravimetry (SAVG) is the determination of the three-dimensional Earth's gravity field from an aircraft using a strapdown inertial measurement unit (IMU).Compared to the classical stabilized-platform spring gravimeters, which are the predominant instrumentation for airborne gravimetry, SAVG offers several advantages:- Strapdown IMUs yield considerable savings in terms of dimensions, weight, power-consumption, and costs. In addition, no operator is required onboard the aircraft.- SAVG enables the determination of deflections of the vertical (vector gravimetry).- Results from recent SAVG campaigns indicate that SAVG can be more robust against turbulence and during manoeuvres.The Physical and Satellite Geodesy group at the Technische Universität Darmstadt (TUDa) proposes to participate in the ANTHALO-BI campaign (cf. separate mission proposal) in scope of this project, providing the instrumentation and an on-site operator. For the SAVG part, the ANTHALO-BI campaign can be seen as scientific feasibility study for the larger ANTHALO Antarctica campaign (scheduled for 2020/21). For both campaigns, the SAVG experiment of TUDa shall contribute the following:- Scalar gravity measurements at the 1 mGal-level (levelled: 0.5 mGal),- deflections of the vertical (DoV), aiming at 0.5 arc seconds precision, and- high-precision, high-rate attitude and heading outputs (expected precision: 3 and 20 arc seconds, respectively).A crucial part of SAVG is an apropiate modelling of the inertial sensor errors. Recent work at TUDa showed, that offline IMU calibration methods can significantly improve the overall SAVG performance, yielding scalar gravity at the level of 1.0-1.4 mGal for recent SAVG campaigns (0.5-0.6 mGal after applying a cross-over adjustment). This is an excellent performance, reaching the accuracy level of the classical spring gravimeters.A particular challenge for SAVG in view of the ANTHALO-BI and ANTHALO campaigns is the inertial sensor stability over long ranges. Therefore, the main objective of this project is the design and evaluation of novel calibration techniques tailored to long-range SAVG, aiming at a higher long-term stability, and also at a greater robustness in dynamic situations, as during manoeuvres and strong turbulence.For this, extended parametric error models including bias, scale factors, and sensor cross-couplings, each as a function of the sensor temperature will be taken into consideration, as well as sample-based (non-parametric) error models. For the evaluation, existing SAVG data sets, which are or will become available to TUDa will be used in addition to the ANTHALO-BI strapdown data sets.This basic research is expected to be a step towards establishing strapdown airborne gravimetry as the default method for airborne gravimetry in the future.