Geophysical Challenges for Future Satellite Gravity Missions: Assessing the Impact of MOCASS Mission

The GRACE/GRACE-FO satellites have observed large scale mass changes, contributing to the mass budget calculation of the hydro-and cryosphere. The scale of the observable mass changes must be in the order of 300 km or bigger to be resolved. Smaller scale glaciers and hydrologic basins significantly contribute to the closure of the water mass balance, but are not detected with the present spatial resolution of the satellite. The challenge of future satellite gravity missions is to fill this gap, providing higher temporal and spatial resolution. We assess the impact of a geodetic satellite mission carrying on board a cold atom interferometric gradiometer (MOCASS: Mass Observation with Cold Atom Sensors in Space) on the resolution of simulated geophysical phenomena, considering mass changes in the hydrosphere and cryosphere. Moreover, we consider mass redistributions due to seamounts and tectonic movements, belonging to the solid earth processes. The MOCASS type satellite is able to recover 50% smaller deglaciation rates over a mountain range as the High Mountains of Asia compared to GRACE, and to detect the mass of 60% of the cumulative number of glaciers, an improvement respect to GRACE which detects less than 20% in the same area. For seamounts a significantly smaller mass eruption could be detected with respect to GRACE, reaching a level of mass detection of a submarine basalt eruption of 1.6 109 m3. This mass corresponds to the eruption of Mount Saint Helens. The simulations demonstrate that a MOCASS type mission would significantly improve the resolution of mass changes respect to existing geodetic satellite missions

Geophysical Challenges for Future Satellite Gravity Missions: Assessing the Impact of MOCASS Mission

AbstractThe GRACE/GRACE-FO satellites have observed large scale mass changes, contributing to the mass budget calculation of the hydro-and cryosphere. The scale of the observable mass changes must be in the order of 300 km or bigger to be resolved. Smaller scale glaciers and hydrologic basins significantly contribute to the closure of the water mass balance, but are not detected with the present spatial resolution of the satellite. The challenge of future satellite gravity missions is to fill this gap, providing higher temporal and spatial resolution. We assess the impact of a geodetic satellite mission carrying on board a cold atom interferometric gradiometer (MOCASS: Mass Observation with Cold Atom Sensors in Space) on the resolution of simulated geophysical phenomena, considering mass changes in the hydrosphere and cryosphere. Moreover, we consider mass redistributions due to seamounts and tectonic movements, belonging to the solid earth processes. The MOCASS type satellite is able to recover 50% smaller deglaciation rates over a mountain range as the High Mountains of Asia compared to GRACE, and to detect the mass of 60% of the cumulative number of glaciers, an improvement respect to GRACE which detects less than 20% in the same area. For seamounts a significantly smaller mass eruption could be detected with respect to GRACE, reaching a level of mass detection of a submarine basalt eruption of 1.6 109 m3. This mass corresponds to the eruption of Mount Saint Helens. The simulations demonstrate that a MOCASS type mission would significantly improve the resolution of mass changes respect to existing geodetic satellite missions

Seamount growth to be observed in future satellite gravity missions

Growing seamounts bear a hazard to navigation, especially if their summit reaches shallow depths and they reach the ocean surface. A seamount that expands up to the surface and creates an island, is detectable by remote sensing images, but not if the island retracts below the surface. Real time gravity observations detect the mass change independently of the optical detection, the limiting factor being only the noise level of the data acquisition in relation to the signal generated by the mass change. Starting from realistic size-frequency distributions of seamounts, we estimate the expected signals of seamount growth. We develop a method to compare the signal to the spectral noise characteristics of a GRACE-type mission, expandable to a possible mission with improved noise curve. We evaluate the expected gravity changes of seamounts and find that a noise curve of GRACE improved by a factor 10 would be sufficient to detect a realistic sea mount growth with a latency of 1 year. The detection threshold though has a tradeoff with the time resolution, since resolution improves for increased time periods over which the satellite observation can be averaged

Geodetic observations to monitor natural hydraulic overpressure

The pressurization of a channel system occurs naturally through intake of rainfall and river drainage. The consequences of up to 1MPa pressurization include sudden uprise of water level, blockage of channels, increased erosion and possible triggering of seismicity, with associated diversified hazards. We model the expected deformation with the Finite Element Method and analytical approaches, and find that the pressures induce deformation which can be geodetically detected. The careful analysis of GNSS timeseries and tilt observations recovered in N-Italy demonstrates that the signals are observable. The observations of tilt have been made in karstic caves where a GPS station has been colocated on the surface. The uplift of GPS during underground floods is expected to be up to several mm and the titling at the microradians level for the tiltmeters. The results demonstrate that geodetic observations could be used to monitor internal pressure loading of the underground channel system. The research is based on the results described in Grillo et al. 2018 and Braitenberg et al. 2019. References Braitenberg C., Pivetta T., Barbolla D.F., Gabrovšek F., Devoti R., Nagy I. (2019) Terrain uplift due to natural hydrologic overpressure in karstic conduits, Scientific Reports, in press. Grillo B., Braitenberg C., Nagy I., Devoti R., Zuliani D., Fabris P. (2018). Cansiglio Karst-Plateau: 10 years of geodetic-hydrological observations in seismically active northeast Italy. Pure and Applied Geophysics, Volume 175, Issue 5, 1765-1781, doi:10.1007/s00024-018-1860-7

SYMBIOmatics: Synergies in Medical Informatics and Bioinformatics – exploring current scientific literature for emerging topics

Background: The SYMBIOmatics Specific Support Action (SSA) is "an information gathering and dissemination activity" that seeks "to identify synergies between the bioinformatics and the medical informatics" domain to improve collaborative progress between both domains (ref. to http://www.symbiomatics.org). As part of the project experts in both research fields will be identified and approached through a survey. To provide input to the survey, the scientific literature was analysed to extract topics relevant to both medical informatics and bioinformatics. Results: This paper presents results ofa systematic analysis of the scientific literature from medical informatics research and bioinformatics research. In the analysis pairs of words (bigrams) from the leading bioinformatics and medical informatics journals have been used as indication of existing and emerging technologies and topics over the period 2000-2005 ("recent") and 1990-1990 ("past"). We identified emerging topics that were equally important to bioinformatics and medical informatics in recent years such as microarray experiments, ontologies, open source, text mining and support vector machines. Emerging topics that evolved only in bioinformatics were system biology, protein interaction networks and statistical methods for microarray analyses, whereas emerging topics in medical informatics were grid technology and tissue microarrays. Conclusion: We conclude that although both fields have their own specific domains of interest, they share common technological developments that tend to be initiated by new developments in biotechnology and computer science

Analysis of direct current resistivity data using continuous wavelet transform

We have developed a new method for the direct current resistivity interpretation, based on the continuous wavelet transform (CWT) of electric potential-difference data. It exploits the main properties of the CWT, such as stability versus noise, and does not require a starting model or other a priori information such as a model weighting function or constraints. Because the approximate integral equation of the resistivity problem has the same form as the forward problem for potential fields, the authors analyze geoelectric data (with dipole-dipole configuration) using the wavelets belonging to the Poisson kernel semigroup. They find that the CWT analysis of the measured electric potential difference is able to identify buried bodies, defining their depth, position, and extent. Such parameters are estimated with no prior knowledge of the resistivity contrast between the bodies and the background. We consider several synthetic models, such as dikes, compact bodies, and contacts. In general, the depth and the lateral thickness of the buried bodies are estimated with good accuracy, using a diagram relating the singular point estimations to the different values of the dipole separation factor n. Thanks to the good results obtained from synthetic data, we test the method with data generated during laboratory experiments. In two laboratory-scale models, our method displays a better precision compared with smoothness-constrained least-squares inversion in identifying the exact position of the edges of a buried body. Finally, we find that combining CWT and inversion is advantageous: after constraining the inverse problem with a priori information from the CWT analysis, we obtain an improved inverse model

Hydrologic induced deformation : Distinguish surface loading from pressure induced uplift

The observation of crustal deformation is a means to calculate the strain rates and the stress loading at faults. The strain rate is expected to vary in time during the earthquake cycle, but also due to hydrologic masses and fluxes. Hydrologic mass is an elastic loading of the crust, with a consequent lowering and return to the starting position. The opposite effect occurs in places in which the subsurface waters are constrained to flow in channels with consequent buildup of pressure of the water, which determines a surface uplift and deformation. This latter effect is present in karst areas, and in particular in the classical karst shared between Italy and Slovenia, where crustal deformation is measured with tiltmeters in caves and GPS at the surface

MOCASS: a satellite mission concept using cold atom interferometry for measuring the Earth gravity field

Both GRACE and GOCE have proven to be very successful missions, providing a wealth of data which are exploited for geophysical studies such as climate changes, hydrology, sea level changes, solid Earth phenomena, with benefits for society and the whole world population. It is indispensable to continue monitoring gravity and its changes from space, so much so that a GRACE follow-on mission has been launched in 2018. In this paper, a new satellite mission concept named MOCASS is presented, which can be considered as a GOCE follow-on, based on an innovative gradiometer exploiting ultra-cold atom technology and aimed at monitoring Earth mass distribution and its variations in time. The technical aspects regarding the payload will be described, illustrating the measurement principle and the technological characteristics of a cold atom interferometer that can measure gravity gradients. The results of numerical simulations will be presented for a one-arm and a two-arm gradiometer and for different orbit configurations, showing that an improvement with respect to GOCE could be obtained in the estimate of the static gravity field over all the harmonic spectrum (with an expected error of the order of 1 mGal at degree 300 for a 5-year mission) and that estimates are promising also for the time-variable gravity field (although GRACE is still performing better at very low degrees). Finally, the progress achievable by exploiting MOCASS observations for the detection and monitoring of geophysical phenomena will be discussed: the results of simulations of key geophysical themes (such as mass changes due to hydrology, glaciers and tectonic effects) with expected gravity change-rates, time constants and corresponding wavelengths, show that an improvement is attainable and that signals invisible to past satellites could be detected by exploiting the cold atom technology

GOCE mission follow-on by cold atom technology: the MOCASS study

MOCASS (Mass Observation with Cold Atom Sensors in Space) is a study project funded by the Italian Space Agency in the framework of preparatory activities for future missions and payloads of Earth Observation. The idea is to propose a GOCE mission follow-on, launching a unique spacecraft with an on-board gradiometer based on advanced cold atom interferometry (CAI) accelerometers and capable of measuring Earth\u2019s gravity gradients along one or two orthogonal directions. The MOCASS project aims at investigating whether this mission concept can improve GOCE results in terms of accuracy and resolution of the estimated gravity field model, and the capability of detecting mass distribution and monitoring mass variations. To this purpose, firstly the instrument characteristics are defined in terms of long-term stability, accuracy, and spectral responses. Then simulations on gravity field recovery based on the space-wise approach already used for the GOCE data processing are implemented. Finally, an analysis on the geophysical signals that can be detected given the simulated mission performance is made. Simulations were assembled by considering real GOCE orbits at different altitudes, but assuming that a CAI gradiometer is on board the spacecraft. This allows a direct comparison between GOCE and MOCASS performances. Instrumental error spectra were defined depending on the orbit and the orientation of the CAI gradiometer arms, considering both a nadir-pointing satellite and an inertial-pointing one. For each configuration, the effect of the satellite angular velocity was computed from the time series of the GOCE orbit coordinates at different altitudes. The resulting instrumental error shows a flat spectrum in the low frequencies, differently from the one of the GOCE electrostatic accelerometers. On the other hand, the interferometer transfer function introduces a strong correlation between close observations. Given the error spectra and the interferometer integration spectral response, observations of gravity gradients were first simulated and then processed by the space-wise approach, which basically consists in a sequential application of a Wiener filter deconvolution, a local collocation gridding and a spherical harmonic analysis. From Monte Carlo sample statistics, the estimation error of the retrieved gravity field model was evaluated for the different mission configurations, showing an improvement in both accuracy and resolution with respect to GOCE. This estimation error was finally compared with the expected gravity signal from selected geophysical phenomena. In particular, the focus was on the India-Tibet region, which involves important and different movements of mass through time and comprises several different crustal structures. The results show that both time-varying gravity signals, like those due to the Tibet-Himalaya glacier melting and crustal uplift, and static gravity signals, like those due to the India seamounts, could be detected by the MOCASS mission