Relative weighting of space and ground colocated laser- and microwave observations in common parameter estimation. An ACES related simulation study
Year: 2025
Type: article
Abstract: Each geodetic observation technique has its noise level and may contain systematic errors. When combined through a common parameter estimation using the least squares methods, it is essential to address their different characteristics. This becomes possible with an appropriate weighting during parameter estimation. In state-of-the-art processing, this weighting is based on the instrument noise of the respective techniques. Thereby, the technique-specific noise characteristics outside the electronic components, such as colored noise of tropospheric turbulences are not considered. This study investigates different weighting approaches for combining microwave and laser observations between one satellite and one ground station. Therefore, the geodetic observatory in Wettzell (Germany) and the Atomic Clock Ensemble in Space (ACES) mounted on the International Space Station (ISS), were selected. The Wettzell station plays an important role in system calibration for this mission. The ACES mission is equipped with a laser-based one-way and two-way ranging system and a microwave-based two-way system comprising an uplink in the Ku band and two downlinks in the S and Ku bands. The investigations are carried out in a controlled simulation environment. This, allows to investigate the influence of different weighting approaches on the accuracy and precision of the parameter estimation. All results are benchmarked with respect to a weighting based on instrument noise and a weighting based on Variance-Component-Estimation. In addition, equal weighting, higher weighting of laser-based observations, and modeling of tropospheric fluctuations as alternative approaches are evaluated. The procedure for relative bias calibration of the microwave system relative to the laser-based system serves as the basis for processing. Since this is a one-satellite to one-station scenario, no precise orbit determination in the conventional sense is performed, only an short-arc orbit fit. The results show that a higher weighting of the laser-based observations minimizes the influence of the tropospheric fluctuations and significantly improves the parameter estimation. The same applies to improved noise modeling in the stochastic model by introducing covariance information from errors not included in the functional model. To sum up, considering different types of noise is more important than their magnitude, up to a certain extent. This result is also relevant for the combination of established geodetic observation techniques such as GNSS and SLR, as these exhibit noise and error characteristics comparable to optical and microwave observations used in this study.
Source: Advances in Space Research
Authors: Peter Vollmair, Anja Schlicht, Urs Hugentobler
Institution: Technical University of Munich
Language: English
Subfield: Aerospace Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $2,780
OpenAlex ID: W4414242822