Disturbance Attenuation and Pointing Control System Design for an Improved Disturbance-Free Payload Spacecraft

Round 1

Reviewer 1 Report

The paper is devoted to a novel technical approach to solve the problem of the low-frequency disturbances transmitted by flexible cables between Payload Module and Support Module. Despite a connection of PM and SM by cable the  spacecraft is called a Disturbance-Free Payload   spacecraft. Authors expect that the low-frequency disturbances on the SM which is proposed to be dominated in disturbances appearance are hoped to be attenuated.

A few small remarks below.

Line 88-89:  It is essential that the TM is spherical so that its attitude motion does not influence the measurement of  the capacitive sensors.

It is true from point of view of gravitational force and torque but what's about Eddy current, changing, magnetic interaction? No word concerned the possible interaction of TM with external Magnetic Field and MF generated by SC units.  

Line 224: (7) is expression rather than equation.

Lines 227-228: This is a key of any controller. If you like to pay attention to an explanation, please, specify the key of PID itself.

Line 256: Such curves are usually called amplitude-frequency response.

Line 279: It is useful to give the main parameters of SDC, orbit the reader to have an idea of what one reads.

Line 316: Explain why polylines are given, not smooth curves. 

Results of numerical simulation just demonstrate but not proved the statements declared. 

Math approach to solve a problem can be explained in more details.

 Maybe the detailed paper can be useful for authors: BENJAMIN LANGE, The Drag-Free Satellite, AIAA JOURNAL, SEPTEMBER 1964, VOL. 2, NO. 9, PP.1590-1606.

Author Response

Dear Reviewer,

Thank you for allowing us to revise our paper entitled “Disturbance Attenuation and Pointing Control System Design for an Enhanced Disturbance-Free Payload Spacecraft (aerospace-2359257). We are also grateful for your valuable comments on this manuscript, including the spherical test mass, the amplitude-frequency response, the main parameters of SDC, etc. We are very grateful to the reviewer for pointing out some mistakes in the manuscript and giving professional revision opinions. The comments and suggestions have been taken into account and the modifications are highlighted in red in the revised manuscript. We hope the revised manuscript can be accepted for publication under the condition of your professional comments and our careful revision. Thank you again for your great help. For detailed responses, please check the document named Responses-to-Reviewer-1.doc.

Author Response File: Author Response.docx

Reviewer 2 Report

1. Please provide the other missions experience for disturbance attenuation in the Introduction.

2. Page 3. Please describe what is the purpose of the attitude pointing control for the payload module control.

3. Page 3. What is the set of electromagnetic actuator. Either it is the pair of magnetorquers or this is it three of such actuators.

4. Page 8. The decoupling can be rather sensitive to the errors of the system parameters. This should be discussed in the paper.

5. Page 10. The model description for the numerical simulation section should be provided. What are the disturbances and external forces and torques are taken into account, what are the position and attitude determination errors etc.?

6. The comparison with other approaches is needed.

Author Response

Dear Reviewer,

Thank you for allowing us to revise our paper entitled “Disturbance Attenuation and Pointing Control System Design for an Enhanced Disturbance-Free Payload Spacecraft (aerospace-2359257). We are also grateful for your valuable comments on this manuscript, including the missions experience for disturbance attenuation in the Introduction, the purpose of the attitude pointing control, the set of electromagnetic actuators, the decoupling design, simulation conditions, comparison with other approaches, etc. We are very grateful to the reviewer for pointing out some mistakes in the manuscript and giving professional revision opinions. The comments and suggestions have been taken into account and the modifications are highlighted in red in the revised manuscript. We hope the revised manuscript can be accepted for publication under the condition of your professional comments and our careful revision. Thank you again for your great help. For detailed responses, please check the document named Responses-to-Reviewer-2.doc.

Author Response File: Author Response.docx

Reviewer 3 Report

1. On line 29, the degree symbols make the numbers look like 10^(-60) and 10^(-70). To avoid this, consider adding additional space or writing at deg/s.

2. It is generally preferred to avoid acronyms in the abstract. I suggest simplifying the abstract to that so many acronyms can be avoided. Focus on clearly stating the problem, methodology/approach, results, and conclusions.

3.  Line 39, how can the PM be isolated from disturbances that act on the PM? Perhaps the second PM should be SM.

4. Line 41, “connection” should be “connected”.

5. The paper is terse. All of the symbology on line 153 is not explained. 

6. It is not possible to replicate the results. For example, it is not clear what gravitational model is used (two-body motion, spherical harmonic perturbations, mascons, etc.). The disturbance model is not included. Initial conditions, integration tolerances, etc. are also not provided. Reference [16] also does not provide this information.

7. How is it possible to feedforward unknown disturbances? Or, for the given disturbance model (which needs to be described), how are the disturbances estimated for feedforward purposes?

8. Results would be more compelling if a statistical analysis were provided rather than one case. Consider doing a Monte Carlo study over various initial conditions, disturbances, etc. As it stands, it may be that the one case shown does not excite some unwanted modes.

9. It is unclear to me why the states are renamed as q variables. For one, this could be confused with the quaternion. And two, it hides the state from the reader. Consider changing or explaining your reasoning in the response letter.

10. Line 258 says "In accordance with the design requirements..." Can you provide these design requirements and show how your gain selections satisfy the requirements? This will also facilitate the reader's replication of results.

The topic of the paper is interesting from an application and control systems perspective. However, the analysis and results presented are nowhere near sufficiently detailed to allow replication or drawing of conclusions. 

I am recommending a major revision so that your revised paper can be more detailed especially when it comes to replicating the simulation and doing a statistical analysis.

Thank you for sharing your work.

The English writing is fine.

Author Response

Dear Reviewer,

Thank you for allowing us to revise our paper entitled “Disturbance Attenuation and Pointing Control System Design for an Enhanced Disturbance-Free Payload Spacecraft (aerospace-2359257). We are also grateful for your valuable comments on this manuscript, including the degree symbols, the acronyms in the abstract, the symbology explanation, the simulation condition, the estimation for feedforward, the model expression, etc. We are very grateful to the reviewer for pointing out some mistakes in the manuscript and giving professional revision opinions. The comments and suggestions have been taken into account and the modifications are highlighted in red in the revised manuscript. We hope the revised manuscript can be accepted for publication under the condition of your professional comments and our careful revision. Thank you again for your great help. For detailed responses, please check the document named Responses-to-Reviewer-3.doc.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The paper becomes better. All comments are taken account.

Reviewer 3 Report

Thanks for your detailed response. You have addressed all of my comments. As a matter of opinion, I would still suggest that the simulation data presented in the paper so that results can be replicated. Your paper is only 14 pages long, and I don't think the journal has a page limit. Nonetheless, I have recommended the paper is accepted and that the editor consider the data/replication issue. Thanks.