LEO Satellite Navigation Based on Optical Measurements of a Cooperative Constellation

Round 1

Reviewer 1 Report

The paper presents a novel Satellite Navigation Based on Optical Measurements of Cooperative Constellation for LEO satellites. 

Overall, the paper is well-written and contains a few typos. 

Here are some of my comments:

- The navigation algorithm could more clear if written in an algorithm structure instead of steps.

- There could be some explanation for why this particular filter and algorithm are used. For example: Why are authors using a batch filter over a sequential filter? 

- Equation between 20 and 21 is unlabeled. Please label that equation. 

- Some in-depth explanation of why the proposed algorithm is superior to state of the art is missing. I suggest authors add a few more references and compare the performance with more algorithms. 

Author Response

Dear reviewer,

We appreciate you very much for the positive and constructive comments and suggestions. Please see the attachment for our response.

Author Response File: Author Response.pdf

Reviewer 2 Report

- The altitude values of the orbits in Table 3 do not correspond precisely to LEO orbits as proposed by the authors in this paper. In addition, there are errors in the description since, in the table, they indicate it in meters and the text in km, but instead, they put the same numbers without applying the conversion.

- Missing the background and state of the art of this work that allows highlighting its contribution.

- A more outstanding description of the constellation used and the dependence of each constellation parameter with the influence on the system and the results is needed.

- The system is proposed for optics; it is necessary to include the results of the optical link budget. At least, it is needed to see its influence, for example, on power and what other optical parameters influence the system. Compare this with an optical link and an RF to see whether the positioning system is profitable.

- The mathematical description is tedious.

- It is recommended to include a table of acronyms.

Author Response

Dear reviewer,

We appreciate you very much for the positive and constructive comments and suggestions. Please see the attachment for our response.

Author Response File: Author Response.pdf

Reviewer 3 Report

1 1.    General

This paper proposed a new cooperative constellation navigation system, which has similar characteristics with the GNSS, for the LEO satellites using the optical measurement. The idea and methods are well introduced, and the concept is verified with simulation. There are minor comments for the improvement of the manuscript.

 2.    Comments

-  It seems that the ordering numbers of the equations are not strictly matched with the numbers at mentions in the text. A careful check for the equation numbers is needed.

-  There are a few badly written sentences in terms of English, so hard to understand them. They should be revised.

-  There is no description of matrix W in Algorithm 1 in the body, so please add it.

-  Referring to lines 476 and above, it seems like the authors may want to show using Figure 11 that: the increased orbital altitude increases the 3D RMS position error; the SPP is more sensitively affected by the orbital altitude than the OD. The first is well understood from Figure 11, but the second is not, because it looks like the SPP and OD have similar slopes for the orbital altitude. So, it may be effective to change the ranges of the left and right y-axes to be proportional to each other. For example, if the left axis has a range of 60 ~ 260 m, then the right axis can have a range of 3 ~ 12 m. By doing so, the readers can understand the second property intuitively from the Figure. This may be applied to Figure 12 also.

Author Response

Please see the attachment.

Author Response File: Author Response.doc

Round 2

Reviewer 2 Report

The Authors' answers have improved the quality of the manuscript. However, I still have some minor questions:

- What is the channel model used? Could they use any channel model from the following reference?

V. M. Baeza, E. Lagunas, H. Al-Hraishawi and S. Chatzinotas, "An Overview of Channel Models for NGSO Satellites" IEEE Vehicular Technology Conference 2022 London.

- Why have they changed the distances for LEO in Table 3, but the results have not changed?

Author Response

Please see the attachment.

Author Response File: Author Response.doc