Continuous absolute g monitoring of the mobile LNE-SYRTE Cold Atom Gravimeter - a new tool to calibrate superconducting gravimeter -
20/09/2016 | 15:00 | Session 4:
Author(s): Sébastien Merlet, Pierre Gillot, Bing Cheng and Franck Pereira Dos Santos
Sébastien Merlet, Pierre Gillot, Bing Cheng and Franck Pereira Dos Santos
Atom interferometry technics allow for the realization of a new generation of instruments for inertial sensing based on laser cooled atoms. We have developed an absolute gravimeter (CAG) based on these technics, which can perform continuous gravity measurements at high cycling rate. This instrument, operating since summer 2009 is the new metrological french standard for gravimetry.
The CAG has been developed to be movable to participate to international comparisons and on field measurement. It took part to several comparisons since ICAG’09 and operated in urban environment and low noise underground laboratory.
The atom gravimeter operates with a high cycling rate of 3 Hz. Its sensitivity is predominantly limited by ground vibration noise which can be rejected thanks to isolation platforms and/or correlation with other sensors such as broadband accelerometers or seismometers. These developments allow us to perform continuous gravity measurements, no matter what the sismic conditions are and even in the worst cases such as during earthquakes. At best, a sensitivity of 5.6 µGal after 1 s measurement time have been obtained down to 0.1 µGal for long term measurement. Presently, the measurement accuracy is 4 µGal, which we plan to reduce to 1 µGal or below.
I will present the instrument, the principle of gravity acceleration measurement and its performances. I will focus on continuous gravity measurements performed over several years and compare with our superconducting gravimeter iGrav signal. It allows us to calibrate the iGrav scale factor and follow its evolution. Especially, a one-month measurement demonstrated that, thanks to the CAG very high cycling rate, a single day gravity measurement allows to calibrate the iGrav scaling factor with a relative resolution of 4.10-4.