Gravity Field Recovery Using High-Precision, High–Low Inter-Satellite Links

Abstract

Past temporal gravity field solutions from the Gravity Recovery and Climate Experiment (GRACE), as well as current solutions from GRACE Follow-On, suffer from temporal aliasing errors due to undersampling of the signal to be recovered (e.g., hydrology), which arise in terms of stripes caused by the north–south observation direction. In this paper, we investigate the potential of the proposed mass variation observing system by high–low inter-satellite links (MOBILE) mission. We quantify the impact of instrument errors of the main sensors (inter-satellite link and accelerometer) and high-frequency tidal and non-tidal gravity signals on achievable performance of the temporal gravity field retrieval. The multi-directional observation geometry of the MOBILE concept with a strong dominance of the radial component result in a close-to-isotropic error behavior, and the retrieved gravity field solutions show reduced temporal aliasing errors of at least 30% for non-tidal, as well as tidal, mass variation signals compared to a low–low satellite pair configuration. The quality of the MOBILE range observations enables the application of extended alternative processing methods leading to further reduction of temporal aliasing errors. The results demonstrate that such a mission can help to get an improved understanding of different components of the Earth system.

Observational Requirements for Long-Term Monitoring of the Global Mean Sea Level and Its Components Over the Altimetry Era

“…The observation geometry, which is mainly in radial direction, results in a significant reduction of striping effects. It was the basis for the gravity mission proposal called "MOBILE" in response to the ESA EE Call 10 (Hauk and Pail, 2019).…”

Next-Generation Gravity Missions: Sino-European Numerical Simulation Comparison Exercise

“…Based on this concept, in 2016 e.motion 2 was proposed as ESA Earth Explorer 9 mission [10]. Another innovative observation concept is high-precision high-low inter-satellite ranging, which was proposed as the MOBILE mission in response to ESA's Earth Explorer 10 call, e.g., [11] and [12]. On US side, the United States National Academies of Sciences, Engineering, and Medicine published the decadal strategy for Earth observation from space [13], where mass change was identified as one of the top five designated observables to be implemented by future US Earth observation missions, in order to ensure continuity and enable long-term mass budget analyses of the Earth system.…”

The Mass Change Designated Observable Study: Overview and Results

“…Our team's thorough review of the scientific literature, mission proposals, and technology development efforts from the past few decades was essential to identify the SST trade space we investigated. The SST architecture trade space included: (a) single in‐line pair (two satellites in the same orbital plane separated in the along‐track direction, similar to the GRACE and GRACE‐FO architectures); (b) single pendulum pair (two satellites with small differences in the right ascenscion of the ascending node and mean anomaly, where an opening angle specifices the angle at the equatorial crossing between the equator and the line of sight between the two satellites; this formation results in a combination of north–south measurements (maximum at poles) and east–west measurements (maximum at the equator), as the satellites progress in their relative orbits (Sharifi et al., 2007); (c) in‐line pair plus a third trailing satellite that forms a pendulum; (d) two in‐line pairs, commonly referred to as a Bender formation (one pair in a polar orbit, one pair in a lower inclined orbit, typically between 65° and 75°) (Bender et al., 2008); (e) LEO‐MEO (low Earth orbit satellite(s) ranging between medium Earth orbit satellite(s) (Hauk & Pail, 2019)); and (f) SmallSat/CubeSat constellation of satellite pairs performing SST. Cartwheel and helix configurations, which have been previously studied (Elsaka, 2014; Wiese et al., 2009), were omitted given their substantial complexity and limited performance benefit relative to the SST configurations we considered.…”