Technology Demonstration of Space Situational Awareness (SSA) Mission on Stratospheric Balloon Platform

Round 1

Reviewer 1 Report

This manuscript demonstrates a dual-purpose star tracker system for SSA missions and compares RSO imaging. This topic is interesting, but it is difficult to find the innovation of the paper. Moreover, there are some problems that have to be considered:

(1)   Given the focal length and the size of the FPA, the field of view of the camera in Table 4 is incorrect.

(2)   The term "IRQ" on page 12 refers to what?

(3)   The Limiting magnitude calculated by Eq.(1) does not consider the motion state of the RSO.

(4)   What are the challenging problems for RSO detection?  Which problem does this manuscript want to solve?

(5)   The format of the references in the paper needs to be improved.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

This paper presents the design and preliminary results for a high altitude weather balloon payload for RSO detection and attitude estimation. The RSO image catalogue generated by this mission (when shared) is of significant value to the SSA community. 

The article is generally well written (with a few minor grammar issues). However, the article needs restructuring in several areas. The distinction between the overall payload, Subpayload 1, and Subpayload 2 are unclear. This is especially true for Section 3 and Section 5 which should be revised prior to publication. 

Two other areas in which the article may be improved are to describe the improvements made with respect to RSONAR I and to validate the theoretical visual magnitude capabilities presented in Section 7.3.1 with the actual magnitudes for the mission. Further comments and feedback are provided below. With these revisions, the reviewer believes this article will be suitable for publication. 

Line 3: The statement, "... tracking of all objects in view at any given time..." could be misconstrued as suggesting that a single spacecraft needs to perform these SSA activities. Authors should rephrase to "as may RSOs as possible" or similar.

Line 29: Cite the convention for object registration.

Line 58: Authors should provide a citation for this that is specific to WFOV cameras.

Line 66: Is the "SBSS" star tracker described here related to the Space Force SBSS constellation? If so, please include this relationship here. If not and if SBSS is not intended to be a mission-specific acronym, please clarify this in the previous section.

Line 71: Define DRDC.

Line 85: It is not clear what the improvements with respect to RSONAR I are. The authors should provide some discussion comparing these two RSONAR missions.

Figure 2a: Authors should annotate the CAD model labelling the subpayloads here as well.

Line 116/Table 3: This text implies that Table 3 shows the full power budget. However, Table 3 appears to show only the subpayload power budgets. Authors should clarify where/if other payload components such as the PDU and OBC are included in the text and/or table.

Line 134: Authors should provide a summary of the Subpayload 1 components here as it is not clear from the text what is considered to be specific to the overall payload vs Subpayload 1.

Line 139: Was this the lens used on this mission? Authors should clarify as this statement, "lens of choice" does not explicitly state if it was used.

Line 142: "Various models of star trackers have been flown..." Authors should confirm if these are various models of the AURICAM star tracker.

Line 157: From Figure 3, this appears to be the OBC for the full payload and not just Subpayload 1. Authors should restructure Section 3 accordingly or update Figure 3 to clarify.

Line 172: UHS Speed Class 1 appears to be a standard. If so, authors should provide a citation for it.

Line 157: Similar to the Section 3.3.2 comment, this appears to be the communications for the overall payload. Section 3 should be restructured to provide overall payload subsystems separately to Subpayload 1 and 2.

Section 3.3.3: It is not clear from this section if RSONAR II had its own RF communications capability or if it used the CSA balloon. Authors should clarify

Section 5.1: It is not clear if this section is describing data acquisition for both subpayloads. Authors should clarify.

Line 304: Authors should specify which star catalog was used.

Section 7.3.1: This theoretical analysis is good for providing the expected capabilities for both cameras. However, given that the authors have field test results, comparing field results of stars with known visual magnitudes to these theoretical values would provide a much stronger contribution.

Line 436: Space missing between "... peak.The..."

Line 541: Space missing between "... payload.We..."

Line 596: Reference error, listing "Aerospace, M." as an author.

The quality of the English language used in this paper is excellent overall. Aside from minor corrections noted above no improvements are required.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

In the article authors of the “Technology Demonstration of Space Situational Awareness (SSA) Mission on Stratospheric Balloon Platform” Randa Qashoa, Vithurshan Suthakar, Gabriel Chianelli, Perushan Kunalakantha, and Regina S. K. Lee  authors demonstrate a dual-purpose star tracker system for future SSA missions and compare two different sensor options for Resident Space Objects (RSO) imaging. It’s sufficiently actual problem while with the number of  RSOs orbiting Earth raising, the risk of collision also grow, and mitigating this risk requires the detection, identification, and tracking of all objects in view at any given time.  Actually, this belongs to the field of Space Situational Awareness (SSA). So in order to develop algorithms for RSO detection and characterization, starfield images containing RSOs are needed. One of the possible directions to realize it is the star trackers using (which usually have attitude determination applications). Using star trackers images in this dual-purpose manner offers, despite their low resolution, seems to be useful for SSA. The existing star tracker technology already in orbit, eliminating the need for the additional equipment to be launched into near Earth orbits.

For this purpose authors used the results of the Resident Space Object Near-space Astrometric Research (SONAR), on a stratospheric balloon, which was the CubeSat-class payload launched in August 2022. It’s demonstrated a dual-purpose star tracker for imaging and results analyzing from a space-like environment, aiding in the field of SSA. The next-generation dual-purpose camera in a 4U-inspired CubeSat platform, named SONAR II was launched in August 2023. With the SONAR II payload, authors developed a real-time, multi-purpose imaging system with two main cameras of varying cost that can adjust imaging parameters in real-time to evaluate the effectiveness of each configuration for RSO imaging. The authors also performed on-board RSO detection and attitude detection  testing such algorithms.

The article “Technology Demonstration of Space Situational Awareness (SSA) Mission on Stratospheric Balloon Platform” consists from ten parts: Introduction, Mission Overview, Payload Design, Payload Development, Modes of Operation, Data Collection, Analysis, Results, Discussion, Outreach, and Conclusions. For my opinion, factually mostly interesting are the Results and Discussion parts, which could be presented in a more expanded form (for the next authors publications), for example interesting results on str. 379, Figure 9, where the distribution of time delays between images during high-resolution 2048x2048 imaging, with the frequency of occurrences on the y-axis and the time difference in milliseconds on the x-axis,  and str. 441, page 15, Figure 14, where two histograms are presented, representing the distribution of pixel intensities from the minimum to maximum pixel values in the images of the 16-bit image from Subpayload 1, and an 8-bit image from Subpayload 2, despite the fact that the article part Payload Development  is auxiliary in accordance with the priorities of the scientific content of the journal Remote Sensing, but intensively occupies a quarter of the seventeen pages of the main text.

Some remarks.

1.                  str. 405, page 12.  The Equation 1 needs the respective reference.

2.                  str. 405, page 12.  For my opinion instead of recording of decimal logarithm  log/10  , it is more appropriate to use signature lg.

This remarks are not do not devalue this work. All of the above allows me to approve of the publication after the minor revisions of the paper “Technology Demonstration of Space Situational Awareness (SSA) Mission on Stratospheric Balloon Platform” by Randa Qashoa , Vithurshan Suthakar, Gabriel Chianelli, Perushan Kunalakantha, and Regina S. K. Lee.

Best regards!

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

The tracking and cataloguing of Resident Space Objects (RSOs) are of great importance for ensuring the safety of spacecrafts. The authors have designed a RSO detection system using low-cost wide field of view (FOV) cameras and conducted flight tests using a stratospheric balloon platform. This work provides valuable reference for relevant researchers.

The following suggestions are provided for the authors:

(1) What are the differences in RSO detection results at different resolutions? It is recommended to provide quantitative results.

(2) For the estimated results of the limiting magnitude in Figure 11, has it been validated by the flight test?

 (3) Can detection results show that the low-cost IDS camera performs the same as PCO camera? Are there any advantages of the PCO camera on certain occasions?

(4) It is recommended to provide a quantitative comparison of RSO detection results for the four types of cameras.

(5) What is the relationship between FOV and resolution? Do they affect each other or not?

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf