Real-Time Deep-Sea Mooring System with Inductive Telemetry and Multi-Sensor Integration: Deployment and Performance in the South China Sea

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper designs, deploys, and verifies an innovative deep-sea real-time hydrological observation system. The system creatively combines inductive telemetry technology with Tiantong satellite communication, integrates up to 25 sensors, and successfully achieves continuous observation for over one year in the South China Sea at a depth of 1247 meters, with a data reception rate >90% and latency <15 minutes. The research topic has clear engineering and scientific value, the technical approach is clear, the data is detailed, and it provides important technical support and engineering practice reference for building the next generation of deep-sea real-time observation networks. The overall framework of the paper is complete, but there is still room for improvement in terms of methodological depth, insightfulness in results analysis and discussion, and language expression. It is recommended to accept after Minor Revision.
1. Section 3.3 points out that communication interruptions are related to the spring tide cycle and attributes them to instability in the buoy's attitude caused by internal solitary waves. This is an interesting finding, but the analysis is somewhat general. Pls provide measured attitude data of the buoy during communication interruptions (such as roll/pitch angles) compared to normal periods, to directly establish a correlation. Pls conduct a quantitative analysis of the relationship between antenna pointing deviation and the signal margin in the Tiantong satellite link budget. Even with a servo-stabilized gimbal, could severe vibrations cause the signal to drop below the reception threshold momentarily? 
2. The current Figures 5, 6, 7, and 8 are more data presentations and lack in-depth analysis of the scientific processes. For example:  Figure 8 shows the flow profiles during the typhoon and mentions near-inertial oscillations. It could further calculate and plot the kinetic energy spectrum, or display the rotation spectrum of velocity vectors in specific depth layers, to quantitatively confirm the characteristics of near-inertial motions. Temperature-salinity profile data can be used to calculate Brunt–Väisälä frequency (buoyancy frequency) profiles when combined with flow shear, which can preliminarily estimate the Richardson number, discussing the potential for water layer stability and mixing. This would greatly enhance the scientific depth of the paper.

Author Response

Reviewer #1

Comment 1:

The reviewer suggested providing measured attitude data of the buoy during communication interruptions and conducting a quantitative analysis of the relationship between antenna pointing deviation and the signal margin in the Tiantong satellite link budget.

Response:

We thank the reviewer for this valuable suggestion. In the revised manuscript, we have added depth data of the communication buoy during the interruption periods. The analysis revealed that communication failures were primarily caused by the buoy being submerged due to strong internal solitary waves, which directly affected antenna alignment. We have included a new figure showing the correlation between buoy depth anomalies and communication interruptions, along with a discussion on how submersion impacts the satellite link margin. This provides a more direct and quantitative explanation for the observed communication outages.

 

Comment 2:

The reviewer recommended enhancing the scientific depth of the data analysis, such as calculating kinetic energy spectra or Brunt–Väisälä frequency profiles to discuss near-inertial oscillations and water column stability.

Response:

We agree with the reviewer that deeper scientific analysis would strengthen the paper. In response, we have added an analysis of near-inertial kinetic energy during the typhoon period, which is now included in the revised Section 3.4.4. However, given that this paper focuses on the design, integration, and field verification of the real-time observation system, we have kept the data analysis concise and relevant to system performance. A comprehensive scientific analysis of the collected hydrological data (including energy spectra, Richardson numbers, etc.) is planned for a subsequent dedicated research paper.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The primary question addressed by this research is how to achieve reliable, long-term, and real-time data transmission from deep-sea subsurface moorings to shore-based centers, overcoming the limitations of traditional oceanographic observation methods. The topic is critically relevant because the deep ocean plays a vital role in regulating global climate and ecosystem dynamics, yet it remains difficult to observe continuously.  Long-term, high-resolution in-situ data is essential for understanding complex phenomena like internal waves, mesoscale eddies, and global climate change evolution. Real-time data is indispensable for operational oceanography, disaster early warning systems (such as tsunami or typhoon monitoring), and accurate climate prediction models. The study's relevance was demonstrated practically when the system successfully captured high-resolution current profiles during the passage of Typhoon Yagi, providing valuable data on ocean-atmosphere interactions. 

The research explicitly targets the "transmission bottleneck"—the difficulty of sending underwater data to shore-based centers in real-time without compromising system survival or data quality. It addresses the limitations of three existing paradigms: Surface Moorings, SubSurface Moorings, Acoustic Telemetry. 

Suggested improvements - 

• During astronomical spring tides and internal wave activity, the surface buoy experienced violent attitude oscillations and rotation. This misalignment of the satellite antenna caused communication interruptions.  The authors should optimize the anchor system design and adopt a low-center-of-gravity, torsion-resistant buoy structure. This would minimize the tilting and spinning caused by strong surface currents, ensuring the directional antenna remains aligned with the Tiantong satellite. 
• To avoid permanent data gaps, the methodology should be upgraded to include automatic data re-transmission capability. The system should buffer data locally during communication blackouts and automatically upload the backlog once the link is re-established. 
• To strengthen the methodology, the authors should compare these theoretical projections against actual voltage depletion rates observed during the deployment to confirm the power budget model is accurate under real-world environmental stressors.

 

Author Response

Reviewer #2

 

Comment 1:

The reviewer suggested optimizing the anchor system and buoy design to reduce tilting and spinning during strong currents, and to implement automatic data re-transmission during communication outages.

 

Response:

Thank you for these constructive suggestions. In response to the communication interruptions analyzed in the revised version, we have integrated several design and functional improvements for future deployments. We plan to increase buoyancy and extend the mooring length to enhance stability and reduce submergence and tilting under strong internal waves and surface currents, thereby maintaining better antenna alignment. The system will be equipped with robust local data buffering and automatic re-transmission capability to prevent data loss during communication outages, ensuring complete data recovery once the satellite link is restored.

Comment 2:

The reviewer recommended comparing theoretical power budget projections with actual voltage depletion rates during deployment.

Response:

We appreciate the reviewer’s suggestion. In the current deployment, we did not systematically record real-time voltage depletion data for direct quantitative comparison with the theoretical power budget model. However, the fact that the system operated continuously and reliably for over one year, with a data reception rate >90%, provides strong indirect evidence that the power supply system functioned as designed under real-sea conditions. In future deployments, we will incorporate voltage monitoring and logging to enable a more detailed and quantitative validation of the power budget. This will be an important improvement for further system optimization.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

I have no comments. Thanks for considering my cooments and improving the content of the paper.