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Multidisciplinary Oceanic Information SysTem

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SMO 1 - Vector Magnetometer - RAW dataset

Metadata

Instrument: Fluxgate Prototype #1
Investigator: Angelo De Santis (INGV)
Project: SMO
Observatory: NEMO-SN1

Citation: Giovanetti, G., Marinaro, G., & Embriaco, D. (2012). Vector Magnetometer dataset (Fluxgate #1 @ 1 sample / 4 sec) from INGV/NEMO-SN1 seafloor platform during SMO project in Western Ionian Sea site (East Sicily), part of EMSO network [Data set]. Istituto Nazionale di Geofisica e Vulcanologia (INGV). https://doi.org/10.13127/MD/807DB7A9-2EF5-4682-8AA3-3EFB9C873A37

Abstract: This sensor provides the three components of the magnetic induction vector in the directions N-S, E-W and Z (vertical). It is a fluxgate prototype developed at INGV laboratories equipped with an inertial platform for levelling control. It provides continuous seafloor magnetic data which are important for two main reasons: a) they extend the magnetic observations from land to the seafloor, improving the spatial distribution in the Italian territory; b) these data are important for the study of short and long magnetic field time variations. The variational data allow us to estimate the resistivity structure underneath the area of observations and possibly to detect some magnetic variations related to some geo-hazards, such as earthquakes and tsunamis.

Purpose: The main aim is the continuous and almost real-time measurement of the three components of the Earth’s magnetic field in a very peculiar environment which in fact has a favorable impact on the quality of the measurements: first, the temperature is more stable at the sea bottom, especially in deep sea sites, so the instrumental drift due to temperature variations is absent or negligible. Second, the water column acts as a natural "shield" to the highest frequencies of the iono- and magnetosphere inducing fields.

Quality of data: The data series is almost complete for this sensor: ~96% of expected bytes has been recorded (see problems below). Althougth built with a 0.5 Hz (1 sample / 2 seconds) sampling rate, this sensor began measuring with a sampling rate of 1 sample / 3-5 seconds until September 22, 2012 (21:51:10) when its sampling rate swiched to its proper samplig rate (0.5 Hz) without an apparent reason. Anyway, ~4% of data are missing because the sensor delays erratically its measurements for 4-5 seconds for unknown reasons.
Since timestamp is associated to data after on-shore acquisition with a resolution of milliseconds, it may seem that there exists a mismatch in sampling rate when rounding to seconds, but it is only apparent (compare to Julian date).
A mismatch between the data timestamp (date/hour) and that coming from the sensor (in Julian format) exists since this latter cannot be changed nor adjusted.
Erratically, during on-shore acquisition some data strings are corrupted and this results in gaps.
Recurrent (hourly) spikes are due to the proximity of the SMO Marine Magnetics Sentinel scalar magnetometer (with 1 hour sampling).