TSC-1 Offner Spectrometer Prototype Characterization

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article in the submitted form can be published in an industry journal, not in a scientific journal. The article has no scientific features, only technical aspects. There is no literature review, which contains only 6 articles. 2 of them were written by the authors of the submitted manuscript.

1. Summary

The manuscript presents the development, characterization, and performance evaluation of the Offner Spectrometer prototype, designed for the Thai Space Consortium's satellite mission. The paper describes the systematic approach to parameter selection and radiometric analysis, highlighting the spectrometer's diffraction-limited performance in Earth observation. The primary contributions include a detailed explanation of the prototype's design, comprehensive optical performance testing, and experimental validation against simulation results.

2. Broad comments

Strengths.

Comprehensive design approach. The article provides a thorough description of the Offner Spectrometer's design strategy, covering material selection, optical alignment, and mechanical structure. Rigorous performance evaluation: The performance evaluation includes wavelength registration, spatial and spectral resolution measurements, and distortion characterization, which offer valuable insights into the spectrometer's capabilities. Application focused. The characterization results are well tied to Earth observation applications, demonstrating how the spectrometer can fulfill TSC-1 mission requirements.

Weaknesses.

Limited literature review. The literature review is sparse, with only six references cited. A deeper exploration of existing work in hyperspectral imaging and Offner spectrometers could strengthen the research context. Technical orientation. The manuscript primarily focuses on technical aspects and lacks a clear scientific novelty angle, making the current version more suitable for an industry journal.

3. Specific Comments

Introduction (Lines 15-72): The introduction provides a high-level overview of the Thai Space Consortium but lacks specific references to similar work in Earth observation spectrometers. Including comparisons to other Offner spectrometers in literature would contextualize the research.

Offner spectrometer development (Lines 41-72): Expand on the rationale behind selecting an Offner configuration over other spectrometer designs for the TSC-1 mission.

Prototype mechanical design strategy (Lines 73-113): Discuss the challenges of using aluminum for optical components and how these were mitigated in the design phase. Explain why commercial kinematic mounts were chosen and whether custom mounts were considered.

Mechanical and optical alignments (Lines 121-142): Include more details on the alignment process and how errors were minimized, especially given the difficulty of aligning off-axis systems.

Light preparing unit setup (Lines 143-173): Provide more information on how the light preparing units were calibrated to ensure accurate spectral and spatial measurements.

Measurement method (Lines 174-189): Clarify the decision criteria for choosing specific measurement points across the Field of View (FOV) for the spatial and spectral resolution tests.

Optical performance (Lines 190-272): Highlight the expected performance benchmarks and how the results compare with simulation and theoretical values.

Signal-to-Noise Ratio (Lines 266-271): Detail the methods used for dark subtraction and how noise was quantified to ensure accuracy in the SNR calculation.

Specimen spectrum measurement (Lines 272-285): Explain the calibration procedure for converting raw data into reflectance spectra.

Conclusions (Lines 286-309): Expand on the implications of the spectrometer's performance for future TSC missions and other potential applications.

4. Conclusion

While the article provides a detailed technical overview of the TSC-1 Offner Spectrometer prototype, the focus on technical aspects overshadows the scientific novelty. Enhancing the literature review, improving clarity on technical decisions, and providing a more comprehensive scientific context would strengthen the manuscript's suitability for a scientific journal. The current version is more suitable for an industry journal.

5. Recommendation

A major revision is required. Specifically, improve the literature review, clarify technical decisions, and emphasize the scientific contributions.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

A detailed report on rigorous testing and the development of an Offner spectrometer.

Is there any novelty in the prototype design? Please include more references if relevant.

A brief introduction to the TSC-11 mission would be useful. How is the spectrometer going to be used? 

What does PTV mean in Table 1 (and 2)?

Line 116: ams CMOSIS CMV -> AMS CMOSIS CMV

Line 216: "from 24.48 µm to 26.40 m" -> 26.40 µm?

Line 272: please include more details on the experiment setup (e.g. leaf species, distance, possibly with a picture) and post processing (i.e. how the corrected data is obtained from the raw data in Fig. 14 right)

Comments on the Quality of English Language

No major issue

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Review of the Article "TSC-1 Offner Spectrometer Prototype Characterization"

 

1. Introduction and objective of the article

The article "TSC-1 Offner Spectrometer Prototype Characterization" discusses the development, characterization, and performance evaluation of the Offner spectrometer prototype designed for the Thai Space Consortium's (TSC-1) satellite mission. The authors present a systematic approach to parameter selection and radiometric analyses, highlighting the spectrometer's diffraction-limited performance in Earth observation.

 

2. Strengths of the article

a) Comprehensive design approach

The article thoroughly describes the Offner spectrometer's design strategy, covering material selection, optical alignment, and mechanical structure.

 

b) Rigorous performance evaluation

The performance evaluation includes wavelength registration, spatial and spectral resolution measurements, and distortion characterization, which offer valuable insights into the spectrometer's capabilities.

 

c) Application-focused characterization

The characterization results are tied to Earth observation applications, demonstrating how the spectrometer can fulfill TSC-1 mission requirements.

 

3. Weaknesses of the article

a) Limited literature review

The literature review was broadened. Exploring existing work in hyperspectral imaging and Offner spectrometers could strengthen the research context.

 

b) Technical orientation

The manuscript primarily focuses on technical aspects and lacks a clear scientific novelty angle, making the current version more suitable for an industry journal than a scientific one.

 

4. Detailed comments and Authors' responses

a) Introduction (Lines 15-72)

The reviewer suggested the introduction should include more specific references to similar work in Earth observation spectrometers. The authors added a comparison with the ENMAP satellite mission.

 

b) Offner spectrometer development (Lines 41-72)

Expand on the rationale behind selecting an Offner configuration over other spectrometer designs. The authors added text explaining the bibliographic review that was conducted and the technical decisions that were made.

 

c) Prototype mechanical design strategy (Lines 73-113)

Discuss the challenges of using aluminum for optical components and why commercial kinematic mounts were chosen. The authors expanded the section on the use of aluminum and decisions regarding mounts.

 

d) Mechanical and optical alignments (Lines 121-142)

Include more details on the alignment process and how errors were minimized. The authors explained the alignment procedure.

 

e) Light preparing unit setup (Lines 143-173)

Provide more information on how the light preparing units were calibrated. The authors added details about the calibration process.

 

f) Measurement method (Lines 174-189)

Clarify the criteria for choosing specific spatial and spectral resolution test measurement points. The authors described the selection of measurement points.

 

g) Optical performance (Lines 190-272)

Highlight the expected performance benchmarks and compare the results with simulations and theoretical values. The authors added comparisons between simulation and experimental results. But is a lack of information on how simulations were performed.

 

h) Signal-to-noise ratio (Lines 266-271)

Detail the methods used for dark subtraction and how noise was quantified. The authors added details on the methodology.

 

i) Specimen spectrum measurement (Lines 272-285)

Explain the calibration procedure for converting raw data into reflectance spectra. The authors described the calibration procedure.

 

j) Conclusions (Lines 286-309)

Expand on the implications of the spectrometer's performance for future TSC missions and other potential applications. The authors added details about possible applications.

 

5. The reviewer suggests considering the following comments on the article "TSC-1 Offner Spectrometer Prototype Characterization":

 

a. Literature review

While the authors have added some references in response to the reviewers' comments, the literature review still lacks depth. A more comprehensive review of recent advances in hyperspectral imaging and Offner spectrometer technology is needed. Including a broader range of studies and comparing the TSC-1 spectrometer with more contemporary and diverse systems would provide a stronger scientific foundation.

 

b. Scientific novelty and contributions

The article should emphasize the scientific novelty of the TSC-1 spectrometer beyond its technical specifications. This could include discussions on how the TSC-1 spectrometer advances the field of hyperspectral imaging, addresses specific scientific questions, or opens new avenues for research in Earth observation.

 

c. Methodological rigor

The methodology section should be more detailed regarding the experimental setup and procedures. For instance, providing explicit calibration routines, error analysis, and validation steps for the measurements would enhance the credibility and reproducibility of the findings.

 

d. Comparison with existing technologies

While a comparison with the ENMAP mission was added, it would be beneficial to include a comparative analysis with a wider range of existing hyperspectral imagers, both spaceborne and airborne. Highlighting the unique advantages or innovations of the TSC-1 spectrometer in comparison to these systems can further underline its scientific contribution.

 

e. Data analysis and interpretation

The data analysis could be expanded to include more sophisticated statistical methods to assess the performance metrics. Additionally, a detailed discussion on the interpretation of the results, especially in terms of their scientific implications for Earth observation, would provide deeper insights.

 

f. Potential applications and future work

The article touches upon potential applications but should delve deeper into specific case studies or simulations showing how the TSC-1 spectrometer can be used in real-world scenarios. Moreover, outlining a clear roadmap for future research and development, including potential scientific experiments and missions that could utilize the TSC-1 spectrometer, would be valuable.

 

g. Validation and peer comparison

Including a section where the results of the TSC-1 spectrometer are validated against known standards or compared with peer-reviewed benchmarks would strengthen the scientific credibility. This could involve cross-referencing with data from other missions or ground-based spectrometers.

 

h. Figures and visual data representation

Enhance the figures and visual data representations to make them more informative. For example, including error bars, confidence intervals, and comparative plots can provide a clearer understanding of the data and its reliability.

 

i. Theoretical background and simulation

The article should include more details on the theoretical models and simulations used in the design and performance prediction of the spectrometer. This could involve a more thorough explanation of the optical principles and simulation software used, as well as any assumptions or approximations made during the modeling process.

 

6. Conclusions and recommendations

While the article provides a detailed technical overview of the TSC-1 Offner Spectrometer prototype, the focus on technical aspects overshadows the scientific novelty. Enhancing the literature review, improving clarity on technical decisions, and providing a more comprehensive scientific context would strengthen the manuscript's suitability for a scientific journal.

 

The authors responded to the reviewer's comments by adding the missing information and improving the article's clarity, significantly enhancing its quality.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf