Observing the Microwave Radiation of the Sun during a Solar Eclipse with a Ground-Based Multichannel Microwave Radiometer

Round 1

Reviewer 1 Report

Manuscript ID: remotesensing-1711675

Type of manuscript: Technical Note

Title: Observing the Microwave Radiation of the Sun During Solar Eclipse with Ground-based Multichannel Microwave Radiometer

Authors: Lianfa Lei, Zhenhui Wang *, Yingying Ma, Jiang Qin, Lei Zhu, Rui Chen, Jianping Lu

 

Nice paper, the excellent design of the experiment. I have only doubt about the accuracy of approximation (12) and its impact on the results. Is there any way to check the accuracy and impact of this approximation? There are some not-so-serious issues for example text after expressions that are in the same sentence should begin on the left margin, and English requires some additional correction. Anyway, it was a pleasure to read this interesting study.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

1. The acronym “TB” for brightness temperature could be unified with “T_B”.
2. Equation 7can be replaced with “ ”.
3. The format in the references could be further unified.
4. Some errors were highlighted in fluorescent as attached manuscript. The authors could double-check the correctness before re-submission.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Dear authors,

thanks for interesting paper, but I have few comments.

1. Please transfer the paper into standard template for this journal
2. I would like recommend to extend introduction  and analyze more relevant papers
3. After usage of the standard template, please start with generic methodology for your study. Without this is a little difficult to study all theory

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 4 Report

This paper presents measurements of the sun by a ground-based microwave radiometer during two solar eclipse events. 

The novelty and application of these observations is not clear to me. Parameters of the sun, such as eccentricity and others, as well as eclipse parameters are well-known and do not need to be determined by microwave radiometers. These observations have quite some uncertainty given their large beamwidth compared to the diameter of the sun seen from the Earth. The observation of the solar eclipse only confirms obvious facts, such as "the larger the fraction of the sun blocked by the moon, the smaller the brightness temperature measured at the ground", which is really not a surprising finding. 

In addition, many of potentially interesting questions, such as the determination of the antenna pattern or the observation of the sun's brightness temperatures have already been done in previous papers by the same authors: 

"Feasibility for Operationally Monitoring Ground-Based Multichannel Microwave Radiometer by Using Solar Observations", Atmosphere (2021) and 

"Measurement of Solar Absolute Brightness Temperature Using a Ground-Based Multichannel Microwave Radiometer", Remote Sensing (2021)

To summarize, I am missing a clear motivation for this study, especially given that most of the ideas are already presented in the two previous articles, and therefore I recommend to reject this manuscript.  

Author Response

Dear Editor and Reviewer:

Thank you very much for your suggestion. 

At present, the ground-based microwave radiometer (GMR) can continuously observe the atmospheric radiation brightness temperature at K- and V-bands, provide valuable information on the temperature, humidity and liquid water structure of the troposphere, it is widely used in meteorology and climate monitoring in last few decades. However, its value and remote sensing application potential of microwave radiometer cannot be full play in other fields.

   According to the theory and our experiment, the GMR can be used to observe the variation radiation of the sun. So we used the sun to measure the GMR antenna pattern, monitor the antenna pointing, evaluate the stability of the radiometer system and measure the brightness temperature of the sun.

A solar eclipse is one of nature's most dramatic celestial performances, solar eclipse rarely happens but fortunately we witnessed two partial solar eclipses on Dec 26, 2019 and Jun 21, 2020 in Xi’an, China. So, we used the GMR to track and observe the sun. This paper introduced the experiment of observing solar eclipse with GMR. In addition, these observation data can be used to calculate the eccentricity of earth orbit.

This experiment broadens the field usage of GMR, it impels the GMR can be used to measure the eccentricity of earth orbit accurately and even to monitor the variation of the solar radiation. So, I hope you will not reject my manuscript.

Round 2

Reviewer 3 Report

Dear authors,

till now I don't see real progress. You mentioned that you are using official template, but it is not true. See https://www.mdpi.com/files/word-templates/remotesensing-template.dot.

Also review of literature in introduction was not extended.

Author Response

Dear editor,

We have revised this manuscript according to the standard template for this journal ( https://www.mdpi.com/files/word-templates/remotesensing-template.dot). In addiation, we added some review of literature in introduction, but  it has rarely been used to track and observe the solar eclipse with an operational GMR.

Kind regards,
Linafa Lei