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Mitigation of Oceanic Tidal Aliasing Errors in Space and Time Simultaneously Using Different Repeat Sub-Satellite Tracks from Pendulum-Type Gravimetric Mission Candidate

Elsaka B., Ilk K. H., Alothman A.

Acta Geophysica

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2015

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Vol. 63, no. 1

301--318

EN

This contribution investigates two different ways for mitigating the aliasing errors in ocean tides. This is done, on the one hand, by sampling the satellite observations in another direction using the pendulum satellite mission configuration. On the other hand, a mitigation of the temporal aliasing errors in the ocean tides can be achieved by using a suitable repeat period of the sub-satellite tracks. The findings show, firstly, that it is very beneficial for minimizing the aliasing errors in ocean tides to use pendulum configuration; secondly, optimizing the orbital parameter to get shorter repeat orbit mode can be effective in minimizing the aliasing errors. This paper recommends the pendulum as a candidate for future gravity mission to be launched in longer repeating orbit mode with shorter “sub-cycle” repeat periods to improve the temporal resolution of the satellite mission.

2

Sub-monthly gravity field recovery from simulated multi-GRACE mission yype

Elsaka B.

Acta Geophysica

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2014

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Vol. 62, no. 1

241--258

EN

Monthly solutions of the current GRACE mission are affected by the aliasing problem. In fact, sub-monthly temporal sampling may reduce the temporal aliasing errors but this will be done at the cost of reduced spatial sampling. Reducing the effects of temporal aliasing can be achieved by setting two pairs of satellites in different orbital planes. In this paper, we investigate the so-called Multi-GRACE constellation to improve temporal and spatial resolution for the GRACE-type mission without deteriorating accuracy. We investigate two scenarios: the Multi-GRACE ΔM that improves the temporal sampling only and the Multi-GRACE ΔΩ that improves the spatial sampling besides the temporal one in time span of only 12 days for the hydrological signal as a time-varying gravity field component. Our findings indicate that the hydrological signal can be submonthly recovered and the aliasing errors can be reduced as well by increasing temporal resolution (sub-month) via the Multi-GRACE ΔΩ constellations.

3

Rosborough formulation in satellite gravity gradiometry

Sharifi M. A., Safari A., Far K. G.

Artificial Satellites : Journal of Planetary Geodesy

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2013

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Vol. 48, No. 1

39--50

EN

Following the launch of CHAMP, a new era was born in the gravity field determination from satellite observations. Many methods have been proposed and applied for the recovery of the Earth’s gravity field from the observations of the satellite missions CHAMP, GRACE and GOCE. This paper deals with the Rosborough formulation in gravity field modelling. This formulation is derived from the transformation of time-wise representation from the orbital into the spherical coordinate systems. Base functions of the Rosborough formulation depend on the type of the functional of the gravity field and the inclination of the orbit. Unlike the space-wise approach, the Rosborough approach can easily deal with both isotropic and non-isotropic functionals. The proposed formulation is implemented on the GOCE data in order to show its efficiency. Numerical results show that the Rosborough formulation is a powerful and efficient tool in the case of GOCE gradiometry data processing.