Mass variation observing system by high low inter-satellite links (MOBILE) – a new concept for sustained observation of mass transport from space

Abstract

As changes in gravity are directly related to mass variability, satellite missions observing the Earth’s time varying gravity field are a unique tool for observing mass transport processes in the Earth system, such as the water cycle, rapid changes in the cryosphere, oceans, and solid Earth processes, on a global scale. The observation of Earth’s gravity field was successfully performed by the GRACE and GOCE satellite missions, and will be continued by the GRACE Follow-On mission. A comprehensive team of European scientists proposed the next-generation gravity field mission MOBILE in response to the European Space Agency (ESA) call for a Core Mission in the frame of Earth Explorer 10 (EE10). MOBILE is based on the innovative observational concept of a high-low tracking formation with micrometer ranging accuracy, complemented by new instrument concepts. Since a high-low tracking mission primarily observes the radial component of gravity-induced orbit perturbations, the error structure is close to isotropic. This geometry significantly reduces artefacts of previous along-track ranging low-low formations (GRACE, GRACE-Follow-On) such as the typical striping patterns. The minimum configuration consists of at least two medium-Earth orbiters (MEOs) at 10000 km altitude or higher, and one low-Earth orbiter (LEO) at 350-400 km. The main instrument is a laser-based distance or distance change measurement system, which is placed at the LEO. The MEOs are equipped either with passive reflectors or transponders. In a numerical closed-loop simulation, it was demonstrated that this minimum configuration is in agreement with the threshold science requirements of 5 mm equivalent water height (EWH) accuracy at 400 km wavelength, and 10 cm EWH at 200 km. MOBILE provides promising potential future perspectives by linking the concept to existing space infrastructure such as Galileo next-generation, as future element of the Copernicus/Sentinel programme, and holds the potential of miniaturization even up to swarm configurations. As such MOBILE can be considered as a precursor and role model for a sustained mass transport observing system from space.

Impact of a novel hybrid accelerometer on satellite gravimetry performance

“…It can be shown that with such a configuration temporal aliasing effects, which are one of the dominant error contributors of singlepair missions like GRACE and GRACE-FO and result in typical striping patterns, can be reduced significantly (in the order of a factor 5 to 10; Wiese et al, 2011, Daras andPail, 2017). Another promising constellation is high-precision high-low tracking between high or medium orbiting and low orbiting satellites (Hauk et al, 2017), a concept which has been proposed to the European Space Agency (ESA) in response to the Earth Explorer 10 call (Pail et al, 2018).…”

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.…”

On the Use of Satellite Remote Sensing to Detect Floods and Droughts at Large Scales

“…Also, ESA launched a feasibility study on NGGM with the use of Laser interferometer for ranging measurements (Dionisio et al 2018). A NGGM based on the innovative observational concept of a high-low tracking formation with micrometre ranging accuracy (Pail et al 2019) is currently being studied by CNES. Eventually also, the reversing of GNSS-based kinematic trajectories of low-Earth-orbit constellations might be able to monitor groundwater evolution (e.g., Bezděk et al 2016 and references therein).…”