Improved compensation of vibrational noise in the laser interferometer with applications in absolute gravimetry
Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography
Final Report Abstract
The main results of the second phase of this project can be summarized as follows. It has been demonstrated that it is possible to solve the problem of ground vibrations in absolute gravimetry by measuring perturbations of the reference mirror and computing a compensating correction. For the TAG-1 absolute gravimeter (Japan), this provides the targeted measurement precision better than 1 μGal. The approach is well applicable for both cornercube and atom gravimeters and is useful for constructing the compact and robust transportable systems. An open question of inverse filtering, as needed to compensate the transfer function of the used accelerometer, is a promising direction of further research. The post-fit residuals provide important information for other options to compensate vibrational noise: it might be useful (i) to include an additional regression parameter to the model (when it is significant), or (ii) to compute the post-fit residuals-based correction (when the input perturbation is recovered), or (iii) to apply the Lp-norm approximation of the trajectory (when the residuals are far from the Gaussian distribution), or (iv) or to upgrade the uncertainty budget. Owing to such actions, the measurement precision of the gravimeters FG5, TAG-1 and IMGC-02 is typically better than 1 μGal, while the corrected result can be shifted by several microgals. However, to prove the useful impact on accuracy, additional efforts outside this project are needed to revise the comparison reference values, since other primary references for absolute gravity do not exist. The same revision is also necessary to verify inclusion of additional error components to the budget of measurement uncertainty, as originated from the developed absolute gravimeter’s transfer function formalism. Various digital fringe signal processing methods can be effectively combined in the same instrument, including the rise-and-fall system, for which the linear regression model is enabled. This increases a confidence in the measurement results. To conclude, the most important theoretical result of the first phase is the developed transfer function formalism, including the two-channel vibration-invariant structure of an absolute gravimeter. The theory covers both corner-cube and atom absolute gravimeters. The second phase of the project successfully proceeded with experiments and important practical implementations of the theoretical findings. Besides, several important open questions emerging from this project will be investigated in a course of improvements of absolute gravimeters developed at the Earthquake Research Institute, the University of Tokyo, Japan, and also in the current and possibly new projects of the Collaborative Research Center SFB 1128 geo-Q (Hannover, Germany). Because of several innovative results and open questions of this project, we consented to continue perspective research and to present new findings in the foreseeable future.
Publications
- (2012) Accuracy assessment of the two-sample zero-crossing detection in a sinusoidal signal. Metrologia 49 413-424
Svitlov S, Rothleitner Ch, and Wang L J
(See online at https://doi.org/10.1088/0026-1394/49/4/413) - (2012) Frequency domain analysis of absolute gravimeters. Metrologia 49 706-726
Svitlov S
(See online at https://doi.org/10.1088/0026-1394/49/6/706) - (2012) On the evaluation of systematic effects in atom and corner-cube absolute gravimeters. Physics Letters A 376 1090-1095
Rothleitner Ch and Svitlov S
(See online at https://doi.org/10.1016/j.physleta.2012.02.019) - (2012) Self-attraction effect and correction on three absolute gravimeters. Metrologia 49 560-566
Biolcati E, Svitlov S and Germak A
(See online at https://doi.org/10.1088/0026-1394/49/4/560) - (2013) Digital fringe signal processing methods in absolute gravimetry IAG Symposium on Terrestrial Gravimetry: Static and Mobile Measurements, 17-20 September, 2013, Saint Petersburg, Russia 117-124
Svitlov S, Araya A and Tsubokawa T
- (2014) Enabling linear model for the IMGC-02 absolute gravimeter. Metrologia 51 304-315
Nagornyi V D, Biolcati E and Svitlov S
(See online at https://doi.org/10.1088/0026-1394/51/3/304) - (2014) Homodyne interferometry with quadrature fringe detection for an absolute gravimeter. Applied Optics 53 3548-3555
Svitlov S and Araya A
(See online at https://doi.org/10.1364/AO.53.003548) - (2015) Compact absolute gravimeter with a homodyne quadrature laser interferometer, 26th IUGG General Assembly 2015, June 22 – July 2, 2015, Prague, Czech Republic
Svitlov S, Araya A, Tamura Y and Tsubokawa T
- (2016) Improving absolute gravity estimates by the Lpnorm approximation of the ballistic trajectory. Metrologia 53 754-761
Nagornyi V D, Svitlov S and Araya A
(See online at https://doi.org/10.1088/0026-1394/53/2/754)
