A Tutorial on Retroreflectors and Arrays Used in Satellite and Lunar Laser Ranging

Round 1

Reviewer 1 Report

Interesting and much useful information in a compact paper. I have attached a file with some notes on typos that may help to improve the paper. Some of the figures are of low quality and possibly need to be redrawn. Irregular spacings appear everywhere, I suspect this is due to some linux editor conversion to pdf, the equation text size is also much larger than the rest of the text.

Comments for author File: Comments.pdf

Author Response

 Reviewer #1 pointed out several typographical errors  which I believe have all been corrected in the manuscript. 

Reviewer #1 also felt that Figures 4,  5 , and 6 were of low quality.  These figures were drawn from past invited PowerPoint presentations I gave in France, Italy, and Germany. Unfortunately, as a semi-retired consultant, I no longer have access to professional artists to support new artwork. I did however attempt to simplify and improve Figure 5. Perhaps, Photonics staff can improve the images?

Micro Channel Plate Photo Multiplier has been changed as suggested.

Many other changes were made in response to comments by Reviewers 2 and 3 and  my own additional material which hopefully has improved the manuscript.

Thank you for your careful attention to the text.

John Degnan

Reviewer 2 Report

The article discusses the basic of retroreflector theory for SLR to artificial satellites and the Moon containing solid vs. hollow types, velocity aberration effects w.r.t. satellite type. It provides the requirements for mm accuracy retros and developments such as 'spoiling' and 'clocking'. 

I recommend the major revision due to:

- poor quality of figures attached or figure missing

- i had problems with understanding some parts of the manuscript, the main conclusions, more explanations are needed,

- very poor text editing, missing commas, dots, spaces etc,

- missing table explanation, figure discussions,

Please find the attached file with detail comments and suggestions.

Regards

Reviewer

Comments for author File: Comments.pdf

Author Response

Dear Reviewer #2,

Thank you for noticing that Figure 1 was missing. That has been inserted in the revised manuscript.

Several typographical and punctuation errors you pointed out have been corrected.

Figure 5 has been modified but, because I no longer have access to an artistic help as a semi-retired technical consultant, my abity to further improve the figure is limited. Perhaps the Photonics Journal can assist me?

The missing reference on line 287 has been provided andthe typos on line 292 have been corrected..

Lines 331 to 333 have been modified to provide additional telescope diameter information on  the early LLR stations.

Much new material has been added to Sections 7 (Lunar Laser Ranging), 8 (Concluding Remarks,) and 9 (References), primarily  in response to comments by  Reviewer #3.

Thank you for your careful review of the manuscript.

Sincerely,

John Degnan

Reviewer 3 Report

The paper discusses retroreflector theory for satellite and lunar laser ranging (LLR). However, some of the discussed issues need an update with respect to the current achievements and progress in the retroreflector construction. The paper intends to be a review paper, however, some recent achievements are omitted. The review paper requires a better and up-to-date literature review, which is not the case in the current version of the manuscript.  

1.      Some figures, such as Figures 4 and 5 are of low quality. The formating, font sizes, etc. should be unified.

2.      NASA developed a new design for the single corner cube for future lunar missions. See Fig. 1 from  Williams, J. G., Boggs, D. H., & Currie, D. G. (2022). Next-generation Laser Ranging at Lunar Geophysical Network and Commercial Lander Payload Service Sites. The Planetary Science Journal, 3(6), 136. https://iopscience.iop.org/article/10.3847/PSJ/ac6c25

The issue of this construction versus the array of retroreflectors should be addressed in detail and discussed in the paper.

And in: https://ntrs.nasa.gov/api/citations/20210025424/downloads/White%20Paper%20Topical%20Next%20generation%20lunar.pdf

3.      Velocity Aberration and Diffraction Patterns for LLR are discussed, e.g., in:

Otsubo, T., Kunimori, H., Noda, H., Hanada, H., Araki, H., & Katayama, M. (2011). Asymmetric dihedral angle offsets for large-size lunar laser ranging retroreflectors. Earth, planets and space, 63, e13-e16. https://link.springer.com/article/10.5047/eps.2011.11.001

Williams, J. G., Porcelli, L., Dell’Agnello, S., Mauro, L., Muccino, M., Currie, D. G., ... & Johnson, N. H. (2023). Lunar Laser Ranging Retroreflectors: Velocity Aberration and Diffraction Pattern. The Planetary Science Journal, 4(5), 89. https://iopscience.iop.org/article/10.3847/PSJ/acbeab/meta

4.      Recently, the first successful two-way laser ranging to the Lunar Reconnaissance Orbiter (LRO) has been conducted using infrared observations from the Grasse station. The construction of the LRA of the lunar orbiter should also be discussed in this review paper, see

Mazarico, E., Sun, X., Torre, JM. et al. First two-way laser ranging to a lunar orbiter: infrared observations from the Grasse station to LRO’s retro-reflector array. Earth Planets Space 72, 113 (2020). https://doi.org/10.1186/s40623-020-01243-w

5.      For SLR tracking of GNSS equipped with flat retroreflector arrays, the satellite signature effect occurs. The effect is different for single-photon detectors (SPAD and C-SPAD) and multi-photon detectors (MCP/PMT). There are some recent studies discussing the issue of the retroreflector response for coated and uncoated GLONASS LRAs, small-size Galileo uncoated LRAs (Galileo FOC satellites) and with front coating Galileo IOV satellites with the specification of the signature effect for each type of LRAs.

As the paper discussed the LRAs for different applications, the performance of the existing LRAs should also be discussed, including GNSS. Moreover, SPAD and MCP detectors tend to act differently for different LRA construction types.  

N/A

Author Response

Dear Reviewer #3,

Thank you for your comments regarding the original version of my manuscript. I had not originally intended to go into as much depth on LLR since I had not been intimately involved in that activity except via dialogues with ILRS colleagues who were. However, in doing so, I hope to have added new and updated insights into the field.

With regard to the quality of Figures 4 and 5 (which was also brought up by two other reviewers), I sadly am unable to access artistic talent due to my current status as a Semi-Retired Consultant. I did make some simplifications and improvements to Figure 5,  but any further improvements will have to be supplied by Photonics.

I have read and added  the LLR references you suggested plus a few others including similar 170 mm single retroreflector studies by Chinese researchers. I also briefly mention and reference the ranging experiments between the Grasse LLR station and the Lunar Reconnaissance Orbiter (LRO) .

In the process of rewriting Sections 6 (Lunar Laser Ranging),7 (Concluding Remarks) , and 8 (References), I took the opportunity to apply my earlier work  in transmitter and receiver optical gain theory and lidar to computing  the  signal strength from the proposed single lunar retro and the much stronger  background lunar surface returns. r Since the surface returns are spread over a wider FOV, the Single Photon Avalanche Diode (SPAD) arrays (also used in my lidars) would appear to be the best choice for detecting the "hot spot" produced by the lunar retro and guiding it to the center of the telescope FOV.

Thank you for your review of my manuscript. I hope you find the revised version suitable for publication.

Sincerely,

John Degnan

Round 2

Reviewer 2 Report

Dear author,

below I am sending small minor comments before publishing:

- despite problems try to improve the quality of previously mentioned figures

- line 158 (in fact only 2 GPS satellites had retros (and they are inactive now) thus I suggest remove GPS from the list or give annotation about these only 2 satellites, or at least do not mention it as first example

- it is unusual that author did not answer to all comments/questions raised by reviewers or at least did not justify why they were ignored  

Dear author,

Please double-check typos, punctuation errors etc. which still can be found within the text

Author Response

I have uploaded new figures 4 and 5 from the original source, i.e. an invited  PowerPoint presentation I gave in Italy a decade ago.  Figure 5 was improperly cropped and a simpler version has been resubmitted . Figure 1 was missing in the original text and is included in the revised version.

With regard to line 158, I have mentioned the fact that only 2 GPS satellites were equipped with retroreflectors whereas the other international navigation satellites all have, or are planned to have, laser retroreflectors attached and GPS is mentioned last as suggested by Reviewer #2.

I believe I have made an honest attempt to address ALL of the comments submitted by the 3 reviewers as evidenced by the major highlighted  revisions to the sections on Lunar Laser Ranging and Concluding Remarks and the expanded Reference list (which goes beyond the specific suggestions of the reviewers). I. appreciate their careful and comprehensive reviews

Sincerely,

John Degnan

Reviewer 3 Report

The paper in the revised form contains no substantive errors and can be accepted for publication. However, the quality of figures in terms of resolution, as well as formatting of equations, etc., must be unified as they do not meet the standards of scientific papers. 

The paper is written by a native speaker. No major English corrections are required. 

Author Response

I see no new comments from Reviewer #3 .. I believe I have responded to the comments in his/her first review via greatly modified and highlighted text in the sections on Lunar Laser Ranging, Concluding Remarks, and an expanded Reference List which includes all of his recommendations plus a few additional ones   As for Figures 4 and 5, I have improved them to the best of my ability. If the Reviewer has not yet read, the revised text, I suggest he/she do so and comment.

Sincerely,

John Degnan