Highly Accurate Radar Cross-Section and Transfer Function Measurement of a Digital Calibration Transponder without Known Reference—Part II: Uncertainty Estimation and Validation

Round 1

Reviewer 1 Report

1. What is the main question addressed by the research?

 

The paper is dedicated to investigation of cross section and transfer function measurements of a digital calibration transponder without known reference. Continuing their previous article on this subject considered the measurements and results, this second article considers their uncertainty estimation and validation.

 

 

2. Do you consider the topic original or relevant in the field, and if so, why?

 

The topic is original and relevant in the field. As a continuation of their previous article, the authors have validated the obtained results and performed a comprehensive uncertainty analysis to estimate the overall radar cross section uncertainty associated with the presented measurement data.

 

 

3. What does it add to the subject area compared with other published material?

 

Authors extended the analysis by a comprehensive uncertainty evaluation along with a validation of the results. Although the measurement setup was originally designed to estimate only the radar cross section of a transponder, the radar cross section of the involved trihedral corner reflector was also estimated. This allowing an independent verification of the estimated radar cross section of the corner reflector with the well-established technique of full-wave finite element method simulations. The lower radar cross section uncertainty and the knowledge of the reference targets frequency dependence will enable a more precise external end-to-end calibration of the SAR systems.

 

 

4. What specific improvements could the authors consider regarding the methodology?

 

There is no need to make any improvements or something else. The authors outlined shortly the current achievements in the field in the introduction, and provided detailed description of the materials and method, as well as the obtained results, their discussion, and conclusions.

 

 

5. Are the conclusions consistent with the evidence and arguments presented and do they address the main question posed?

 

The conclusions are consistent with the evidence and arguments presented in the manuscript and address the main questions of their study. Nevertheless, authors should outline the future research perspective in Conclusions.

 

 

6. Are the references appropriate?

 

The references are appropriate. Nevertheless, authors should abbreviate journal names, provide missing DOIs, date of access to the internet sources, dates and places of the conferences and similar events in the References section.

 

 

7. Please include any additional comments on the tables and figures.

 

All the tables and figures are appropriate. They show well the research and experiment details and results.

Please, place table captions over the tables. Please, enlarge text in Figure 2.

 

 

8. Other comments.

 

Use ‘Equation ()’ instead of ‘Eq. ()’ in the text.

Author Contributions paragraph should be prepared exactly in accordance with the journal template.

From my point of view, the Abstract should be rewritten providing more information namely on this paper but not about previous one.

 

 

After detailed consideration of the manuscript, I have found that the results obtained are new and significant for the field. The manuscript is written well but needs some corrections before its publication in the journal.

 

 

So, the paper needs at least a minor revision.

Author Response

Dear reviewer,
thank you for reviewing our paper and for your helpful suggestions.

5. We have added an outlook to the conclusions and suggest extending the frequency range of the measurement to other frequency bands.

6. Lot lot of information has been added to the references. In particular missing DOIs and dates of conferences

7. Table captions have been moved above the tables. 
Figure 2 has been enlarged.

8. We have replaced "eq." by "Equation".
Authors' contributions have been edited to follow the journal template.
The abstract has been adapted to focus more on the current paper, its approach and its results.

Reviewer 2 Report

Table 2: please explain the values in dB for the Total lines.

Figure 4 : could you explain the small bias between FEKO and the 3 Transponder Method ?

Add TCR to the abbreviations list.

line 175: what is "ed" ?

line 206: remove double "in"

 

Author Response

Thank you reviewer 2 for the valuable suggestions.

Table 2: The heading for the "Total" row has been renamed to "Total Range Uncertainty". Additionally, a reference to eq. (5) has been added to the table caption.

Figure 4: The small bias between our 3 transponder measurements and the FEKO simulation can be attributed to imperfections in both the simulation and the measurement. The FEKO simulation assumes perfect 
electrically conducting (PEC) material and does not take into account the depth of the metal plates. The paint on the corner reflector is also not included in the simulation. The measurement will
also never be perfect. Therefore, the remaining bias is a good indication of how well the simlation and measurement fit together and gives an indication of the combined simulation and measurement accuracy.

Added TCR to the abbreviations list.

line 175: isolated "ed" was removed.

line 206: double "in" was corrected.

Reviewer 3 Report

This paper par excellence present the uncertainty Estimation and validation for highly accurate radar cross section and transfer function measurement of a digital calibration transponder without known Reference. The calibration method was proposed in their former paper, which I have reviewed. In my opinion, this paper is well written, the method is convincing, and the topic is good for Remote Sensing. 

 

This paper is already qualified for publication.

Author Response

Thank you for your very positiv review.