Autonomous Navigation Based on the Earth-Shadow Observation near the Sun–Earth L2 Point
Round 1
Reviewer 1 Report
The paper by Li et al. must be seriously improved to become acceptable for publication. At this stage, it is more a sketch than a paper. The difference is an error budget. At this stage, only the method is presented, but an error analysis, that is the difference between theory and practice (i.e. a usable navigation method), is totally absent. Another point that can be source of problem is that the the Sun is not a solid body, but a ball of gases. As a result, the Sun boundary (the limb of the Sun) is poorly defined, with a diameter of the Sun that can varies by tens of kilometers depending on the optical wavelenght considered (astronomers use a 520 nm wavelength very often for this purpose). The Sun has also a little flattening, even if it is very very small. The Earth itself is surrounded by an atmosphere that blurs the transition between surface and vacuum. All of this is "under the rug" at this stage. Another annoying point is that at the beginning, the authors do not provide any numers about the precisions of the navigation methods already in use. They need also to provide basic information about the L2 point (distance, what are halo orbits, their stability, etc..).
Author Response
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Reviewer 2 Report
In many places in the text 'spaces' between certain words are missing - must be corrected.
Author Response
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Reviewer 3 Report
Is the use of earth shadow in this paper is the first time novel in the world? Or it is modified from others? Make it clear in Section one with a statement. Is there any related work, for comparison of the results between techniques? What about complexity analysis? Also provide the use of the equations in the simulation. Which result use which equation for easier the reader to reproduce and check validation of the results. Other comments are as follow.
1) Lines 15, 23, 60, 66, 68, 81, 85, 112, 113. Put a space between a word and citation, also between dot and the beginning of sentence, also before comma -> check also other lines, there are so many missing space
2) Line 68. What does “this paper” refer to? This sentence use past tense however. It should be in present tense. Past tense means expired and not valid
3) Lines 85, 115, 172. Put comma before “respectively”
4) Two lines below line 91. Write L with math symbol font for consistency
5) Replace the image of Figs. 1 and 2 with high quality one. For example EMF, WMF, etch to obtain highest quality in PDF
6) Why D_1 axis in Fig. 1 is not labelled as z?
7) Punctuate the equations because they are part of sentences
8) Line 167. Move the dot of the end of above sentence
9) The images in Figs. 5 and 7 are too small
10) Add more information of Fig. 7 regarding to the curves. It is still not clear
11) It is better to assign a subfigure number of each image/curve in Figs. 7 - 10 then explain clearly one by one
Author Response
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Round 2
Reviewer 1 Report
The authors did a very good job in addressing the points raised in the first round of review.
I just ask them to mention in the introduction that the accuracy of navigation reached can reach up to a few centimeters in relative position / Earth, and a few MICRONS / second for Doppler tracking in Ka band / Earth (values for the ESA Bepi-Colombo spacecraft, you will find reference papers easily).
Author Response
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Reviewer 3 Report
The authors has addressed my comments except the equations that have not been punctuated yet.
Author Response
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