On-Orbit Calibration of the KBR Antenna Phase Center of GRACE-Type Gravity Satellites
Round 1
Reviewer 1 Report
Dear authors,
thank you very much for this study. It is well written and the results are clearly presented. I have a few minor points marked in the attached PDF, which should be addressed in a revised version.
Furthermore, I have two general questions.
Why do you seprate the polynomial fitting/reduction and the LS-/M-estimation adjustment? I guess, you could also estimate polynomial parameters and the KBR APC parameters together in one LS-/M-adjstment.
Did you apply any weighting stochastic modeling for your observations O-C values within your LS-/M-procedures?
Kind regards
Reviewer
Comments for author File: 
Comments.pdf
Author Response
Dear Reviewers,
Thank you very much for correcting my many spelling mistakes and English writing norms, I have revised it. Really appreciate.
For the first algorithm problem you proposed, I have repeatedly considered it in the past two months and tried to get better results, but failed to get them. When the polynomial order is 3, a low-precision result can be obtained based on KBR; When the polynomial order is 4, cannot obtain a result based on KBR; When the polynomial degree is 5, neither based on KBR nor KBRR can obtain a reasonable result. And the Normal matrix of KBRR and KBRA is singularity all the time.
In the LS-estimation and the initial weighting of M-estimation, the weight matrix of the observed value is taken as the identity matrix in this paper. When weighted least squares (Weighted by inverse ratio of residuals squared) are used, the KBR APC results didn't change much, but the accuracy can be greatly improved. However, this weighting strategy needs to be used prudently. Because it greatly reduces the weight of observations with large residuals, but it is not necessarily reasonable. M-estimation based on IGG-3 is a compromise scheme adopted in this paper. In the following research results, a better weighting scheme will be considered.
Kind regards
Author
Reviewer 2 Report
The article is interesting, current, decently legible and reasonably understandable.
A few things to fix:
line 129: error in Fig. No. - 6, not 7. Unfortunately, the figure is very far from the text.
line 200: the abbreviation LOS is not explained
missing space at lines 56, 256, 257
References:
1) the year of issue is indicated differently.
2) 5 of the 14 references are in Chinese. Is there really no citation in English?
Author Response
Dear Reviewers,
Thank you very much for your diligent review.
Some editing errors have been corrected and the references format has been unified.
Unfortunately, the people who have the opportunity and interest to do this research are researchers directly involved in GRACE-Type satellite systems, so there are few references in this direction. And there are two relevant English literatures, but they cannot be downloaded.
Kind regards
author
