Configuration Stability Analysis for Geocentric Space Gravitational-Wave Observatories

Round 1

Reviewer 1 Report

This paper studies the configuration stability of a geocentric gravitational-wave detector, such as the proposed TianQin space-based observatory. It does that by looking at the propagation of the configuration uncertainty with time with the method of the e Unscented Transformation (UT), as previously done in Adv. Space Res. 2021, 67, 3744–375 for the case of a heliocentric orbit. A comparison with Mont Carlo (MC) methods is also provided, showing a better computational efficiency of UT with respect to the latter.

Overall, this article constitutes a valuable contribution toward the development of the research about space-based gravitational-wave detectors in geocentric orbits.

The general exposition is well presented and organized, with many figures and tables representing the principal results and some sound interpretations of the results. The bibliography is also adequate for the purpose of the characterization of proposed space-based, geocentric gravitational-wave detectors.

The main issue that I have found is some lack of editorial care, especially in some parts of the text and figures. Though the usage of English is generally fine, some additional proofreading is required. Specifically:

- I suggest using hyphens in compound attributive nouns and avoiding the plural. that is: "gravitational-wave observatory" instead of "gravitational waves observatory" [e.g. Line 39], etc.

- The punctuation and the usage of capital letters at the beginning of paragraphs are sometimes not correct [e.g. L.81,84].

- I think the word "special", used for example in terms like "special directions" [L.12,92, etc.], should be replaced with "spatial".

- It seems there is an "i" instead of a "\dot{l}" in Eq.4.

- The symbols n_x,y,z used in Fig. 7, 8 and 9, although quite intuitive, are not referenced in the text. I suggest adding them in the paragraph at L.279-284. Also, in the same figures, the label of the colorbars (predicted STD on arm length etc.) are missing.

- In Figures 3, 5, 9 and 10, lines with different colours are largely superimposed, despite the usage of different line styles. While this is probably intentional in the case of Fig.5, with the comparison of MC and UT results, the lines on the background are largely hidden by that on the front. Maybe changing also the line transparency (alpha parameter) can help.

- In Tables 5, 7 and 8, there is a repetition in the subscript of the breathing angles. Change une 2 with a 3.

Moreover, the presentation of the statistical quantities related to the stability indices in Section 2.1 can be improved, as this is at the base of the entire study described in this article and some additional comments should be advised, for example about the interpretation of x, y and P, and why only the second order moments are considered (this should be the case of a stationary and Gaussian random variable). Notice also the typos in the inline equations in [L.143] and [L.148].

 

I invite the authors to take into consideration the above recommendations/suggestions for minor edits to the submitted manuscript.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Report on the paper "Configuration Stability Analysis for Geocentric Space Gravitational Wave Observatories"

 

The paper presents a research about the stability of geocentric gravitational wave observatory from the view of the configuration uncertainty propagation. The effects of the orbit insertion errors on the configuration stability are propagated using the Unscented Transformation (UT).

 

The paper can be accepted for publication with minor corrections, and the authors must address the issues listed below before I can recommend acceptance.

 

The observations are the following:

 

Major issues:

 

1. Originality:

The paper is original because they use by first time Unscented Transformation in TianQin project.

 

2. A clear separation of hypothesis, methods and conclusions:

The structure of the article is adequate, the sections are in order, the hypothesis and conclusions are clear, the relevance of their research is shown.

 

3. Clarity of analysis:

The structure and analysis of the paper is clear. They make a comparative result using UT and Monte Carlo result and obtain a comparative result. They obtain a better estimation on time in comparison with Monte Carlo simulations. The stability domain of the geocentric gravitational wave observatory is computed and analyzed.

 

Finally, they found that the radial position and the tangential velocity insertion errors have the most significant effect on the configuration stability and the normal position and velocity insertion errors have the least effect on the stability.

 

 

 

Minor issues.

 

1. Typo in line 42 “parametersthe”

2. Explain better the caption in figure and tables

3. Typo in line 82 “. And”

4. A figure with orbital elements must be included

5. In figure 1 they don’t described who is RXJ0806.3+1527

6. A better explain must be addressed in the formula 1, how it was obtained

7. Typo in line 143, “l|_ij”

8. Typo in line 148 “x_0(t)))”

9. Typo in table 5 “Monta”

10. Typo in line 375 “he”

11. Typo in line 382 “out of line”

12. Explain what is JGM3 in line 110

 

Author Response

Please see the attachment

Author Response File: Author Response.pdf