Reducing Non-tidal Aliasing Effects by Future Gravity Satellite Formations

One major error source in temporal gravity recovery is temporal aliasing. The satellite mission GRACE suffers from pure along-track observations of its low–low Satellite-to-Satellite Tracking (SST) on a polar orbit. This leads to the typical North-South striped error structures in time-variable gravity fields of GRACE, which are amplified because of the inherent GRACE inverse problem and downward continuation. This study analyzes the possibilities to reduce the non-tidal aliasing effects by formations of future gravity satellite missions. It concentrates on mission options which shall be feasible in the next 10 years. These options contain so-called pendulum formations and double pairs with pairs on orbits with different inclinations. Sharifi et al. Previous studies already analyzed several such mission options and this study on the one hand leads to comparable conclusions for the mission options studied in the cited papers. On the other hand combinations of two low–low SST pairs on polar and sun-synchronous orbits, respectively, which are not studied in the cited papers in detail, and its potential to reduce temporal aliasing are analyzed here. This paper focusses on non-tidal temporal aliasing effects together with typical low–low SST noise characteristics. With semi-analytical simulations it is analyzed that a noise level of \(\mathrm{{10}}^{\mathrm{-11}}\,\mathrm{\mathrm{m}\mathrm{/}\mathrm{{s}}^{\mathrm{2}}}/\sqrt{\mathrm{Hz}}\) of the range acceleration observations is sufficient to get sensitivity for mass variations on the Earth. Comparing the effects of non-tidal aliasing and colored observation noise, closed-loop simulations of ten different future mission options are analyzed. Pure along-track low–low SST observations like GRACE in a so-called in-line formation are highly affected by this temporal aliasing. The double pairs containing an in-line pair on a 63^∘ inclined orbit reduce the aliasing effect most. Both the single pendulum pairs, one on a polar and another on a sun-synchronous orbit, and their combination reach the same level of aliasing reduction as the combinations with the 63^∘ inclined pair.