Research Progress of Dynamic Measurement Technology of Atom Gravimeter

Round 1

Reviewer 1 Report

Reports

In the submitted manuscript, the authors first review the main research papers on the atomic gravimeter, especially its dynamic measurement technology. Then, it presents the reported principle, scheme and dynamic measurement equipment of an atom gravimeter. The generation mechanism and suppression methods of the main sources of dynamic measurement error, such as vibration noise, accelerometer drift and dynamic carrier effect, are analyzed. Finally, prospects for applying the dynamic measurement technology of the atomic gravimeter in the mapping of the gravitational field, navigation and detection of underwater targets are explored. The authors point to the state-of-the-art for several essential characteristics of gravimeters. Highlighting mainly those related to dynamic characteristics and a vast and relevant updated bibliography is discussed in the manuscript. They add a separate section on temperature effects and an experimental apparatus, in Fig. (1) and Fig.(7), used in their measurements. It is imperative to emphasize, however, the preliminary character and few measurements of these types of gravimeters. In the opinion of the authors themselves comes through the sentence: "Currently, field measurements of atomic gravimeters are mostly static or quasi-dynamic stop-and-go experiments, and dynamic measurement research is still in its infancy" . The work is important due to the bibliography and the analysis of the characteristics of the relevant models and experiments on this type of meter. They also emphasize that: the accelerometer must have high precision, therefore, the error of the accelerometer itself cannot be ignored. For example, the influence of environmental factors, such as temperature or the structure of the device itself, makes the accelerometer oscillate. The authors certainly indicate the main methods that can be involved in the entire measurement process, do not conflict with each other and can be used all or only some of them to inhibit accelerometer drift; i) first is to add a temperature control system; ii) second is to model and compensate for accelerometer temperature drift, collect the drift data at different temperatures; iii) third is to compare the exact gravity value obtained by the atomic gravimeter with that of the accelerometer to obtain the drift value and deduce it.

It is a good and extensive bibliographic work on the state-of-the-art on gravimeters, a project of an experimental apparatus and a very promising beginning of measurements, but little progress. However, there are some points that deserve further attention:

1 - Check the flow of Eq. (1). Definition of Df = (keff . g - 2pa)T2, with a= keff . g. Rewrite Eq.(1) so that Df can be a number between zero and 2p.

2 - Fig.(2) is the same as Fig.(2) of the cited reference with Ref.(41) with some improvement, but without the citation of the original figure or its authors.

3 - The sensitivity function h(t), from Eqs.(5) and (7), has no phrase or expression showing its characteristics.

4 - A point where the work of the present manuscript is described concerns the experimental setup for the experiment - Fig.(1), was not much explored in measurements. It would be advisable to have more data with this self-developed apparatus and its measurements to give greater understanding and support to the gravimeter model in evidence, and a consistent comparison with current gravimeters.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

Thank you very much for your time involved in reviewing the manuscript and your very encouraging comments on the merits. We also appreciate your clear and detailed feedback and hope that the explanation has fully addressed all of your concerns. In the remainder of this letter, we discuss each of your comments individually along with our corresponding responses. To facilitate this discussion, we first retype your comments and then present our responses to the comments in a different color(blue).

Comments:

In the submitted manuscript, the authors first review the main research papers on the atomic gravimeter, especially its dynamic measurement technology. Then, it presents the reported principle, scheme and dynamic measurement equipment of an atom gravimeter. The generation mechanism and suppression methods of the main sources of dynamic measurement error, such as vibration noise, accelerometer drift and dynamic carrier effect, are analyzed. Finally, prospects for applying the dynamic measurement technology of the atomic gravimeter in the mapping of the gravitational field, navigation and detection of underwater targets are explored. The authors point to the state-of-the-art for several essential characteristics of gravimeters. Highlighting mainly those related to dynamic characteristics and a vast and relevant updated bibliography is discussed in the manuscript. They add a separate section on temperature effects and an experimental apparatus, in Fig. (1) and Fig.(7), used in their measurements. It is imperative to emphasize, however, the preliminary character and few measurements of these types of gravimeters. In the opinion of the authors themselves comes through the sentence: "Currently, field measurements of atomic gravimeters are mostly static or quasi-dynamic stop-and-go experiments, and dynamic measurement research is still in its infancy". The work is important due to the bibliography and the analysis of the characteristics of the relevant models and experiments on this type of meter. They also emphasize that: the accelerometer must have high precision, therefore, the error of the accelerometer itself cannot be ignored. For example, the influence of environmental factors, such as temperature or the structure of the device itself, makes the accelerometer oscillate. The authors certainly indicate the main methods that can be involved in the entire measurement process, do not conflict with each other and can be used all or only some of them to inhibit accelerometer drift; i) first is to add a temperature control system; ii) second is to model and compensate for accelerometer temperature drift, collect the drift data at different temperatures; iii) third is to compare the exact gravity value obtained by the atomic gravimeter with that of the accelerometer to obtain the drift value and deduce it.

It is a good and extensive bibliographic work on the state-of-the-art on gravimeters, a project of an experimental apparatus and a very promising beginning of measurements, but little progress. However, there are some points that deserve further attention.

Point 1:

Check the flow of Eq. (1). Definition of Df = (keff . g - 2pa)T2, with a= keff . g. Rewrite Eq.(1) so that Df can be a number between zero and 2p.

Response 1:

Thank you for pointing out our error. We have rewritten the relevant content of this equation in the revised manuscript and corrected some errors.

Point 2:

Fig.(2) is the same as Fig.(2) of the cited reference with Ref.(41) with some improvement, but without the citation of the original figure or its authors.

Response 2:

We draw this figure to introduce the basic principle of atom gravimeter more clearly. After introducing, we have cited several related literatures, including ref. [41], i.e., line 156 in the original manuscript.

Maybe you are referring to ref. [40] because we did not find a similar figure in ref. [41]. We added a citation of ref. [40] here.

This figure is very classic and appears in almost every reference dealing with the basic principles of atom gravimeters. We have improved it according to our own understanding, mainly concerning the number of atoms of the two paths in the interference process. In addition, to unify the style with Fig.3, we have made some adjustments in the color.

Point 3:

The sensitivity function h(t), from Eqs.(5) and (7), has no phrase or expression showing its characteristics.

Response 3:

We supplemented the relevant expression of h(t) in equation (6) of the new manuscript according to ref. [35].

Point 4:

A point where the work of the present manuscript is described concerns the experimental setup for the experiment - Fig.(1), was not much explored in measurements. It would be advisable to have more data with this self-developed apparatus and its measurements to give greater understanding and support to the gravimeter model in evidence, and a consistent comparison with current gravimeters.

Response 4:

Thank you for your very excellent advice. In fact, we are also making efforts on this. In the next step, we will use this setup to conduct gravity measurement experiments at sea to verify its stability and environmental adaptability.

Thank you again for your valuable comments and suggestions.

Yours sincerely,

The Authors

Reviewer 2 Report

The paper presents comprehensive review on dynamic measurement of atom gravimeter by focusing on the sensitivity of past instruments, measurement principle, error sources, and application prospects. The paper is worth for publication but the reviewer feels that some discussions should be added as a future prospects for the field.

- In section 4, the possible applications are presented, but the required sensitivity is mentioned only in 4.3. It would be good to discuss required sensitivities even with some specific examples for other application directions, which help reader to know the current situation and what is needed toward the applications.

- In section 4, since the paper focusing on the dynamic measurements, the expected velocity for each application and requirements for progress should be mentioned.

 

Author Response

Dear Reviewer,

We would like to thank you for your efforts in reviewing our manuscript, and providing many helpful comments and suggestions, which will all prove invaluable in the revision and improvement of our paper.

To facilitate this discussion, we first retype your comments and then present our responses to the comments in a different color(blue).

Comments:

The paper presents comprehensive review on dynamic measurement of atom gravimeter by focusing on the sensitivity of past instruments, measurement principle, error sources, and application prospects. The paper is worth for publication but the reviewer feels that some discussions should be added as a future prospects for the field.

Point 1:

In section 4, the possible applications are presented, but the required sensitivity is mentioned only in 4.3. It would be good to discuss required sensitivities even with some specific examples for other application directions, which help reader to know the current situation and what is needed toward the applications.

Response 1:

Thank you for your comment. We increase the discussion in the revised manuscript on the required sensitivity and accuracy of devices for other possible application directions. However, we think that not all application directions emphasize accuracy and sensitivity, for example, in navigation, what is more important is that the atom gravimeter does not have drift and does not need regular correction, which brings new opportunities to passive inertial navigation in long voyage. We have also added these discussions to the revised manuscript.

Point 2:

In section 4, since the paper focusing on the dynamic measurements, the expected velocity for each application and requirements for progress should be mentioned.

Response 2:

There are few literatures involved in the expected velocity and progress requirements of atom gravimeter dynamic measurement in these application directions. However, we have made some possible speculations based on the application of traditional devices in these areas, which are reflected at the end of each section of 4.1~4.3 in the revised manuscript.

We would like to take this opportunity to thank you for all your time involved and this great opportunity for us to improve the manuscript. We hope you will be satisfied with this revised version.

Yours sincerely

The Authors