Error Sources of Interferometric Synthetic Aperture Radar Satellites

Round 1

Reviewer 1 Report

This paper is fairly well structured. This paper provides an in-depth analysis of various error sources of InSAR. Furthermore, the authors make the thorough comparisons for effect of errors of different band SAR satellites. This work is of great significance on the deep understanding of InSAR technique for both beginners and experts in the field. The manuscript is well written. However, there are still some details that need attention, as follows:

1)       The paper makes an emphasis on the error sources of InSAR satellites, it is suggested that the title becomes “Error Sources of Interferometric Synthetic Aperture Radar Satellites”

2)       Orbit error is a fundamental error source which determines the phase error (flat-earth and orbit phase errors) and location error. The authors should make a comprehensive analysis on orbit error rather than categorizing orbit error as orbit phase error.

Author Response

This paper is fairly well structured. This paper provides an in-depth analysis of various error sources of InSAR. Furthermore, the authors make the thorough comparisons for effect of errors of different band SAR satellites. This work is of great significance on the deep understanding of InSAR technique for both beginners and experts in the field. The manuscript is well written. However, there are still some details that need attention, as follows:

I'm grateful for your positive feedback on the structure, depth of analysis, and the overall significance of our work in the field of InSAR.

1)       The paper makes an emphasis on the error sources of InSAR satellites, it is suggested that the title becomes “Error Sources of Interferometric Synthetic Aperture Radar Satellites”

Thank you for the suggestion. We will make the necessary changes to reflect this improvement.

2)       Orbit error is a fundamental error source which determines the phase error (flat-earth and orbit phase errors) and location error. The authors should make a comprehensive analysis on orbit error rather than categorizing orbit error as orbit phase error.

I appreciate your comment regarding the orbit error analysis in our paper. I would like to clarify that while the focus of the paper includes an exploration of orbit error's influence on orbital phase errors, the primary objective is to provide a comprehensive overview of various error sources in InSAR. The section discussing orbit error aims to synthesize and organize past studies on how orbit error contributes to InSAR orbital phase. While the paper may not delve extensively into a new comprehensive analysis of orbit error, it synthesizes and arranges existing knowledge on this aspect.

For example, for Section 3.1.2. Flat-Earth Phase and Section 3.1.3. Orbital Phase, we cited works from Ferretti et al., 2007; Massonnet and Feigl, 1998; Zebker and Rosen, 1996; Hanssen, 2001; Li and Goldstein, 1990; Rodriguez and Martin, 1992; Tkachenko, 2009; M. Liao et al., 2020; Wang et al., 2021; Fattahi & Amelung, 2014 etc.

Since flat-earth phase is usually corrected during the InSAR processing, and the orbital phase is usually ignored thanks to extremely precise orbit determination satellite platforms (these reasonings are mentioned in the paper), the review for these two error sources is fewer than some the other sections.

I hope this clarifies the paper's intention, and I am open to further suggestions or guidance on how to enhance this aspect of the manuscript.

Reviewer 2 Report

This paper summarizes the error sources and their budgets on InSAR processing by dividing those errors into two categories, i.e., intrinsic height errors and location induced errors. The content of the paper is suitable for InSAR primary researchers, however, those sources effects are investigated thoroughly in previous works, such as the random effects on InSAR processing (Zebker, H.A., Villasenor, J., 1992. Decorrelation in interferometric radar echoes. IEEE Transactions on geoscience and remote sensing 30, 950–959.).

Though the authors listed the main error sources on InSAR processing, I recommend them that at least one real InSAR system data, like the TerraSAR-X/TanDEM-X or the Sentinel-1, should be used to further verify the theoretical analysis effects of error sources.

 The quality of English is well organized 

Author Response

This paper summarizes the error sources and their budgets on InSAR processing by dividing those errors into two categories, i.e., intrinsic height errors and location induced errors. The content of the paper is suitable for InSAR primary researchers, however, those sources effects are investigated thoroughly in previous works, such as the random effects on InSAR processing (Zebker, H.A., Villasenor, J., 1992. Decorrelation in interferometric radar echoes. IEEE Transactions on geoscience and remote sensing 30, 950–959.).

I appreciate your insightful observation regarding the investigation of error sources in previous works, particularly the study by Zebker and Villasenor (1992). In the introduction of my paper, I did acknowledge the early InSAR literature, including works by Zebker, H.A., and Villasenor, J. (1992), emphasizing the exploration of error sources connected to imaging geometry, propagation path, and InSAR processing. I also provided a comprehensive historical overview of early research efforts, including works by Li and Goldstein (1990), Rodriguez and Martin (1992), and Hanssen (2001), highlighting the evolution of InSAR error analysis. In response to your suggestion, we rewrote the second half of the “Introduction” in which we (1) will add specific sentences to the paper (i.e., Zebker and Villasenor, 1992) and (2) reiterate the distinctive contributions of this work.

Though the authors listed the main error sources on InSAR processing, I recommend them that at least one real InSAR system data, like the TerraSAR-X/TanDEM-X or the Sentinel-1, should be used to further verify the theoretical analysis effects of error sources.

We would like to highlight that in our review paper, we meticulously derived many of the error metrics, plots, and figures using parameters from current and upcoming SAR sensors. As a comprehensive review paper, our focus is on synthesizing existing knowledge and presenting a broad overview of various error sources in InSAR processing. Incorporation of real satellite data enhances the applicability and relevance of our findings, but that would be beyond the scope of this review paper. We hope this clarification addresses the reviewer's concern, and we remain open to further suggestions or feedback.

Reviewer 3 Report

I would like to thank the authors for pointing out an important addition in the literature and making a general evaluation. A nice and organized study has been done on the sources of errors that occur in the processing of SAR images. It has become a reference work for researchers who will conduct SAR studies. The compilation of studies from past to present has also added richness.

However, I have a suggestion for authors. You should also mention phase unwrapping parameters in your future studies. Because changing phase unwrapping parameters may cause general errors in SAR applications. This affects the accuracy of the application.

There is a minor revision below. After this correction, I think the article is suitable for publication.

-Title 4.3 is used 2 times. (see Volume decorrelation and Noise decorrelation)

Author Response

I would like to thank the authors for pointing out an important addition in the literature and making a general evaluation. A nice and organized study has been done on the sources of errors that occur in the processing of SAR images. It has become a reference work for researchers who will conduct SAR studies. The compilation of studies from past to present has also added richness.

Thank you for your insightful feedback on our paper. We are thrilled to hear that you consider our study a well-organized and valuable contribution to the literature on SAR image processing. Your positive evaluation is motivating, and we appreciate your thoughtful comments. 

However, I have a suggestion for authors. You should also mention phase unwrapping parameters in your future studies. Because changing phase unwrapping parameters may cause general errors in SAR applications. This affects the accuracy of the application.

Thank you for your valuable suggestion. While we did not explicitly mention phase unwrapping parameters in our study, we emphasized the significance of errors arising from phase unwrapping, underscoring the need for further discussion. Our intentional decision to refrain from delving into extensive details of phase unwrapping aligns with our focus on systematic and random errors associated with SAR applications. We appreciate your input and will consider incorporating additional details in future studies.

There is a minor revision below. After this correction, I think the article is suitable for publication.

-Title 4.3 is used 2 times. (see Volume decorrelation and Noise decorrelation)

Thank you for noticing this mistake. It has been corrected.

Round 2

Reviewer 2 Report

The response is reasonable to my concerns. I have no further comments.

The English expression is clear and readable.