IMGC-02: metrological characterization of a new transportable absolute gravimeter

Over the past thirty years the development of transportable ballistic absolute gravity meters has dramatically improved the ability to measure the local acceleration g due to gravity. The application of new technological advances and the deep study of the physical phenomena influencing the absolute measurement of g allowed significant improvements in accuracy. Nowadays the future progress is expected to reduce instrumental size, weight, costs and to increase the operational simplicity of the instruments rather then to improve the accuracy. Nevertheless we point out a lack of information concerning the estimate of the uncertainty in g measurements that is fundamental to compare measurements performed by different instruments. In particular, according to our knowledge, a comprehensive analysis carried out following the Guide to the Expression of Uncertainty in Measurements ISO-GUM is still missing. The purpose of this paper is to highlight the influence parameters in measurement with an example of the metrological characterization of a transportable absolute gravimeter fulfilling the guidelines of the ISO-GUM. The example concerns a rise-and-falling absolute gravimeter: the IMGC-02. In particular we present: i) the complete list of the influence factors of the measurement, (characteristic of the instrument and of the observation site), ii) details concerning the assessment the most overriding effects, in particular those due to the retroreflector balancing, the verticality of the laser beam and the Coriolis acceleration, iii) the uncertainty budget with tables reporting the instrument and measurement uncertainty, iv) experimental results showing the measurement repeatability and reproducibility achievable with the IMGC-02.