Design of Orbit Controls for a Multiple CubeSat Mission Using Drift Rate Modulation

Round 1

Reviewer 1 Report

The paper is devoted to feasibility study of a mission to test laser communication between two 6U-Cubesats. The use of Cubesats give advantage but otherwise provides harder requirements for orbital motion control and quite more complicated simulation approaches. With remarks let's go through the text referring to the line numbers.

45-46: The paper provides  a ballistic aspects of the mission but there is now system description itself. Even there is no description of thruster characteristics which effect very much the dynamics of the Cubesats. For instance, description of results are given under assumption that delta V lies in the orbital plane.   Violation of this assumption can destroy the developed theory of a relative distance control inevitably.

 69: How laser communication can effect the relative distance?

74-76: While orbits of both SC have the same inclination by initial conditions then satellites can move permanently in same orbital plane. Difference in J2 perturbation can provide different effect on both satellites if their orbits have different inclinations, for instance, due the initial relative velocity provided by deploying but in this case they do not move in the same  plane. So, given phrase is not correct.

77: term "drift rate modulation" must be clear explained because:

78-80: it is not clear why this method can precisely maintain a relative position without determining the relative orbit.

112-113: LVLH coordinate system (CS) and relative CS are mentioned. "Moreover, \bold R,S,W in Fig.2 represents LVLH RS". How mane RS are introduced one or two? If  \bold R,S,W is LVLH RS then \bold S cannot  point along direction of the satellite velocity because in non-circular orbit R and velocity vector are not perpendicular. 

142-143: Why five cycles of laser communication is enough? May be it is too many? Provide a comment.

146: +/-10 km for 10 days - why such an accuracy for 10 days? Clarify.

217: What is it \lambda? What does it mean (AoL, \lambda)? Definition, scalar product? Clarify.

217-218: argument of latitude is equal to si=um of argument of perigee and true anomaly rather than mean anomaly. It can be correct for circular orbit. For elliptical orbit it is wrong. In such a case formulae and conclusions made below can be non-correct and have to be checked.

224:  no explanation of "e".

225-230: Conclusion what terms have to be taken into account are not proved and looks like a bla-bla. 

  295: typo.

301-302: Of course, MOEs have less deviation but satellite along the orbit around the Earth is obeyed J2 and described by COE. So, conclusion that MOE is better to use than COE due their less value has to be clarified.

350-353: This explanation should be moved to the text. This remark concerns other  long captions both to tables and pictures.

366-370: To maximize velocity change delta V should be parallel to the satellite velocity. It is well-known fact and does not require such ornate discussion.

384: Here and below instead of R_s component of velocity it is better to use delta V_s.

407: How authors can provide delta V value with accuracy of 10^{-4} m/s.   

458-459:  velocity and position errors have different dimensions and compare them via 1/1000 is not correct. 

 574-575: What is a novelty in pulse control use to adjust a relative distance? This is standard technique. 

606-607: Is a number of contract-grant available for support? Otherwise, what is a support?

614-615: Is Michael a family name? What is a source? 

618-619: Is it a paper in Proceedings. Provide a reference.

620-621: Source?

622: Source?

631-632: Proceedings or what? 

Author Response

Please see the attached document.

Author Response File: Author Response.docx

Reviewer 2 Report

This paper investigates relative distance control with drift and shows parametric studies.

 

- VISION mission is not proper for keywords.

• Introduction only describes the mission and laser commutation systems. Related methods and research for orbital control should be described.
• In Section 2.1, S axis is assumed to be along the satellite velocity. However, this is only the case for circular orbits.
• Related to the previous question, is the orbit in this paper a circular orbit? Please define the orbit specification clearly.
• In Section 4.5, the definition of the thrust direction error is unclear, because the thrust direction has two degrees of freedom, i.e., azimuth and elevation. Please explain and define the thrust direction clearly.
• This paper discusses the results using the relative distance only. However, the relative distance between two satellites is usually time-varying. Especially, if delta V has error, two satellites no longer stay at the same orbit. Additional figure that shows three dimensional relative position using relative orbital elements(ROEs) would be helpful for clearer understandings.

Author Response

Please see the attached document.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Thank you authors for scrupulous work and accepting remarks. The paper, indeed, looks better. However, a few last steps have to be done.

Lines 620-621: As soon as study was granted by the Program the number of grant/contract should exist and shown otherwise it looks as a declaration.

Lines 628-629: The name is shown but there is no source indication. Please, indicate (book, paper, etc and where it was published).

Line 636: Since it is thesis, please, indicate MS or PhD Thesis.  

 

Author Response

Please see the attached file.

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript has been revised according to the reviewers' comments.

However, "VISION mission" should be removed from keywords.

Author Response

Please see the attached file.

Author Response File: Author Response.docx