GRACE and GRACE-FO Related Publications (no abstracts)

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Tailored accelerometer calibration by POD for thermospheric density retrieval with GRACE and GRACE-FO

Wöske, Florian, Huckfeldt, Moritz, and Rievers, Benny, 2024. Tailored accelerometer calibration by POD for thermospheric density retrieval with GRACE and GRACE-FO. Advances in Space Research, 74(10):4517–4542, doi:10.1016/j.asr.2024.09.021.

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@ARTICLE{2024AdSpR..74.4517W,
       author = {{W{\"o}ske}, Florian and {Huckfeldt}, Moritz and {Rievers}, Benny},
        title = "{Tailored accelerometer calibration by POD for thermospheric density retrieval with GRACE and GRACE-FO}",
      journal = {Advances in Space Research},
     keywords = {Precise Orbit Determination (POD), GRACE/-FO, Accelerometer, Thermospheric density, Non-gravitational forces},
         year = 2024,
        month = nov,
       volume = {74},
       number = {10},
        pages = {4517-4542},
     abstract = "{The density of the upper atmosphere can be determined by orbit and
        accelerometer data from low Earth orbit satellites as insitu
        measurements along the orbit. One main challenge therein is the
        estimation of physical accelerometer calibration parameters,
        meaning that these parameters should not absorb other effects
        and model deficiencies in the Precise Orbit Determination (POD)
        process. The accelerometers of all geodetic satellites like
        GRACE and GRACE-FO are affected by time dependent bias and scale
        factors. Therefore a calibration of the data is indispensable. A
        dynamic POD based physical accelerometer calibration is
        developed for the complete GRACE and GRACE-FO missions. We
        investigate different parametrization strategies and utilize
        different observation data, as the accurate inter-satellite
        ranging additionally to GPS orbit data. For the estimation
        parameters we distinguish between offset and scale, furthermore,
        cross-track and radial directions are significantly less
        sensitive than along-track and require a different evaluation.
        For the offset, constant and time dependent parameters are
        investigated. Furthermore, a continuous offset calibration over
        arc boundaries is implemented and tested. The sensitivity of the
        scale factor is lower, although, in contrast to the offset, it
        increases with higher total accelerations. This means that it
        needs to be estimated over longer time periods. We investigate
        periods between three hours and one month as well as results
        from Gravity Field Recovery (GFR). Monthly scale factors give
        valuable results, at least for x-axis and when the Solar
        activity is not very low. Nevertheless, we also estimate
        weighted constant scale factors from the monthly results and use
        these in a subsequent POD, giving more realistic offset results
        for most periods and cross-track and radial directions. From the
        used background models in the POD, Earth's gravitational model
        has a noticeable influence on the estimated calibration
        parameters, especially the scale factors. We utilized several
        different models. Results with monthly ITSG solutions are
        distinctly better than the ones with the time dependent GOCO06s
        model. We show that the validation with usual metrics, like
        post-fit POD residuals, is not able to reflect the quality of
        the different estimated calibration parameters. For a
        quantitative validation we introduce an approach based on the
        modeled non-gravitational accelerations. Therefore, the
        uncertainty of the models is evaluated first. The influence of
        main error sources in the models is assessed and propagated to
        the results. We compare our scale parameters to available
        references and the complete calibration to TU Delft's latest
        results. Finally we show the effect of different calibration
        options on the retrieved density. The estimated calibration
        parameters and non-gravitational accelerations for the whole
        GRACE and GRACE-FO missions are available on our data server
        www.zarm.uni-bremen.de/zarm\_daten.}",
          doi = {10.1016/j.asr.2024.09.021},
       adsurl = {https://ui.adsabs.harvard.edu/abs/2024AdSpR..74.4517W},
      adsnote = {Provided by the SAO/NASA Astrophysics Data System}
}

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