TY  - STD
AU  - V. Korepanov, A. Marusenkov
PY  - 2010//
TI  - Observatory magnetometer in-situ calibration
N2  - XIVth IAGA WORKSHOP ON GEOMAGNETIC OBSERVATORY INSTRUMENTS, DATA ACQUISITION AND PROCESSING; September 13 – 23, 2010; Changchun, Jilin Province, China.The magnetic observatories are continuously striving to improve the accuracy of the field measurements. A renewed interest came up recently for instruments using a scalar sensor placed into the center of a coil system (see references below). They are able to reach very high accuracy , but at the expense of relatively high own noise background. So far, the majority of the observatories are still equipped by flux-gate or even photoelectric variometers. The baseline of these types of variometers are estimated using well-known absolute measurements, whereas the scale factors and orientation of the sensor reference frame, which are implicitly involved into the computation of the absolutes values of the field, usually are poorly known and almost everywhere not calibrated periodically, as should be required. The absence of the periodical calibration can be partly explained by fact that the metrological certification of the instruments should be provided in special laboratory by means of calibrations coils what requires to interrupt the measurements, transport the instrument to and from the calibration site and reinstall it again in the observatory. This way of doing is absolutely unacceptable, especially for remote observatories, because the time taken by the whole procedure can be very long, resulting in large gaps in the records. There is also a calibration method based upon magnetometer rotation in the approximately constant Earth’s magnetic field. However, whereas this method gives acceptable precision for, e.g., satellite magnetometers, it is not applicable to observatory magnetometers, due to the actual limited range of field variation, the large relative errors and the possibly unequal scale factors. In addition, the issue of the in-situ orientation of the triaxial magnetometer remains unsolved if we are seeking high accuracy.	In this report we continue to discuss the possibility to calibrate in-situ the observatory instrument based upon the comparison of its records with the field recorded simultaneously by a reference magnetometer. The certified reference instrument has to be installed close to the tested one, its sensitivity axes properly oriented with respect to the geomagnetic frame and the records as synchronous as possible.	The improved version of the observatory magnetometer LEMI-025 was specially designed as a reference instrument. In order to check practical aspects of the proposed in-situ calibration procedure two such magnetometers calibrated using a reference coil facility have been installed in the Strasbourg University geophysical station for intercalibration. The results obtained by processing synchronous records as well as the reliability of these results and estimations of the errors involved into the in-situ calibration procedure are discussed.
N1  - exported from refbase (http://publi.ipev.fr/polar_references/show.php?record=982), last updated on Tue, 30 Nov 1999 00:00:00 +0100
ID  - V.Korepanov2010
ER  -