Improving the Pulse-Limited Footprint Resolution of GNSS-R Based on the Novel Joint Bandwidth Method
, Wei Zheng 1,4,5,6,7,*,†, Fan Wu 3,†, Xiaoping Li 1, Keke Xu 5, Xiaofei Ma 2, Jinwen Shi 2, Xiao Tao 2, Cheng Zhu 8 and Xingang Zhang 2Round 1
Reviewer 1 Report
This manuscript proposed to use the novel joint bandwidth method to use the combination of Galileo E5a and E5b signal to improve the pulse limited footprint resolution when using GNSS-R for wind retrievals. The method was described in detail and the conclusion is convinced. Therefore, I believe this manuscript can be considered for publication in Remote sensing after some revisions.
(1) this manuscript focus on the pulse limited footprint resolution of GNSS-R, which I think is more important to GNSS-R altimetry than wind retrievals. Though there is one sentence in Line 122-124 to express the importance of the pulse limited footprint resolution on wind retrievals, the importance of requirement of high-resolution wind is not correctly described. Meanwhile, as described in line 103-119, the wind speed was retrieved by using DM fitting or DDM-related parameter, and the ACF of the E5a/b NJBW joint signal in Figure 8 is multimodal, therefore, I doubted that the multimodal ACF will have bad influence on the precision of wind retrievals. However, the pulse limited footprint resolution is vital to GNSS-R altimetry, and the sharp peak of ACF is helpful for high-precision retrieval of sea level. Therefore, why does the author focus on the pulse limited footprint resolution of GNSS-R wind retrievals not altimetry?
(2) The use of reference [21-30] is not good. The main points should be described in detail for every reference.
(3) English needs minor revisions. And some abbreviations need to be given the full name the first time they are mentioned, such as VSWR in Line 380 and RF in Line 396.
(4) In Line 483-485, “It can be seen from Figure 9 that compared with the TSFB E5a signal, the nadir pulse limit footprint size of the E5a/b NJBW joint signal reduces from 3.8 km to 2.2 km, which is 0.58 times”. As we all know, the footprint size is related to the elevation angle, therefore, where can we get the value of 3.8 km and 2.2km？ Please make it clear.
(3) English needs minor revisions. And some abbreviations need to be given the full name the first time they are mentioned, such as VSWR in Line 380 and RF in Line 396.
Author Response
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Author Response File: 
Author Response.doc
Reviewer 2 Report
You may describe the contribution of your paper whether antenna you designed and signal processing method.
Your contribution is performed based on simulation by using some model.
Why didn't you use real Galileo signal for verify your method even though you have antenna and algorithm.
I have read the similar article that study the similar situation with car equipped receiver and analyzing received Galileo E5a&b signal and provided 5 meter resolution.
Please find more realistic study based on your antenna and signal processing.
OK to me
Author Response
Please refer to the attachment for details.
Author Response File: Author Response.doc
Round 2
Reviewer 2 Report
Test with real small sat may be recommended as your future work.
Even test with drone is possible near term verification with your work.
