Review Reports

Round 1

Reviewer 1 Report

Summary: The manuscript entitled "Rapid Detection and Orbital Parameters Determination for Fast-approaching Non-cooperative Target to the Space Station Based on Fly-around Nano Satellite" by Sun et al. explores the non-cooperative target detection strategy and algorithm by using angles-only measurements from two cooperative vehicles. The theoretical results are verified by simulations. Generally, this can give practical usefulness and possibility of expansion for orbital guidance problems. From this point of view, it addresses interesting issue for publication in Remote Sensing.
Recommendation: Generally this paper is well organized and written. However, in this time the current manuscript is not so enough to support publication in Remote Sensing. I recommend this paper for a minor revision.
Comments and Suggestions: Below are some comments and suggestions that emerged while reviewing the paper.
1. There are some English grammatical mistakes and ambiguous meaning expressions. I suggest the authors update the whole paper. Maybe asking proofreading service from native English speaker is a good choice.
2. Suggest the authors highlight their contributions.
3. Suggest the authors provide more the explanation for the notations in the formula. It is not good for letting the readers guess the definition.
4. Text paragraph after the Eq.(3) need not be a new paragraph.
5. Please note that the format of the references should be completely in accordance with the examples in the template.
6. The review of the latest work made by others is not so sufficient. Suggest the authors update the introduction.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

In this paper, a novel rapid detection and orbital parameters determination method based on the collaborative observation of a space station and fly-around the nanosatellite is developed. Considering the nano-satellite's observation constraints, the non-cooperative target detection strategy is provided, and the detection efficiency is analyzed. Then the orbital parameters filtering model of the non-cooperative target based on the collaborative observation is constructed, and the Unscented Kalman filter method is utilized to determine the orbital parameters of the non-cooperative target.

In general, the paper is good but I have some comments:

1-       English language and style need to little modification.

2-       In my opinion, it needs improvement both in terms of design and presentation of the results.

3-      why this UKF filter is chosen for analysis? If the standard Kalman filter or the least squares method fails or does worse, it would be a big plus to show it. More specifically, it remains unclear why UKF is used, and whether there are problems with predicting the error area of the state vector in the problem.

 

4-      There is very little information on the composition of the measuring information (it is all model, as far as I understand). It would be interesting, in addition to the graphs of the velocity and position errors from the article, to have information on how the measurements are consistent.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Dear editor and authors,

 

Manuscript ID

remotesensing-2152092

 

Rapid Detection and Orbital Parameters Determination for Fast-approaching Non-cooperative Target to the Space Station Based on Fly-around Nano Satellite

 

With the objective of fast detection and determination of the orbital parameters of the rapidly approaching non-cooperative target, in this manuscript a new method of fast detection and determination of the orbital parameters based on the collaborative observation of the space station of nanosatellites is proposed. The nanosatellite and space station fly-around configuration is designed for coverage scanning of the early warning region around the space station. Then, the filtering model of the non-cooperative target's orbital parameters is established and the Unscented Kalman filter (UKF) method is used to determine the orbital parameters. This work proposes to improve the observability through the orbital maneuver of the nanosatellite. As one of the results, if only the camera on the space station is considered for scanning in the alert region, the probability of covering the alert region is only 66.27% limited by observation constraints, while it reaches 97.36% with based on collaborative nanosatellite observation. Thus showing an excellent result.

The manuscript has scientific merit that can be published. I recommend the publication, here are just a few comments listed below.

 

 

1)    What is the source of Figure 1? Please indicate the source in the caption.

 

2)    Please define variable n from equation 1.

 

3)     How were the calculations made to arrive at equation 2? I believe that the authors should describe more about these accounts.

 

4)     In “As shown in Figure 8(b), set r=25 km , the nano satellite is always located at 25 km in front of the y axis in the LVLH coordinate system, the red point represents the nano satellite and it maintains following flight with the space station.”

In this case, the red dot would not be the non-cooperative target ?

 

 

5)    What is the country of the publications below? China? I suggest reviewing the references.

 

Dang Z.H. Research on Modeling and Control Method of Spacecraft Cluster Boundary [D]. National University of Defense 532 Technolog, 2015.

 

Luo Y.Z. Research on Spatial Optimal Rendezvous Path Planning Strategy [D]. National University of Defense Technology, 2007.

 

6)    Were references 17 to 20 published in English? I did a search and didn't find any of them. This makes it difficult to verify some equations.

Same for references 2, 3 and others.

Author Response

Please see the attachment.

Author Response File: Author Response.docx