Immersive Virtual-Reality-Based Streaming Distance Education System for Solar Dynamics Observatory: A Case Study
Round 1
Reviewer 1 Report
The authors present a highly relevant paper that has merit to be published in a journal such as Applied Sciences.
The paper reports on the development process of an Immersive Virtual-Reality-based Streaming Distance Education System for Solar Dynamics Observatory and its evaluation in an experimental and exploratory study with students.
They present a solid review of related literature and work and present the development of the system in appropriate detail. Congratulations on a job well done.
In the experimental dimension, they begin by presenting and describing the technical requirements of the client and network systems for using the IVR-SDO system. They introduce and characterize the 20 selected participants. In this aspect we think you could detail a little more the process of choosing these participants. Why these participants? How were they recruited?
Regarding the Likert-type questionnaire, how was it developed, how were these items defined? Was the 14-item scale validated in advance? How?
Please, can you give more details to the reader?
In the results section, the authors describe the main results of the experimental study, however, a discussion of these results related to the literature review or other related work is missing if possible. Can connections be made between the results of the experimental study and other similar studies?
Congratulations on the excellent work that has been done, which deserves to be divulged and disseminated to the scientific community.
Author Response
Response to Reviewer 1 Comments
Point 1: In this aspect we think you could detail a little more the process of choosing these participants. Why these participants? How were they recruited? 

Response 1: We updated the manuscript by adding the following section explaining the recruitment and selection of the participants (page 12, line 368; page 13, line 377).
4.3.1. Participants
We recruited 20 unpaid participants (7 females) aged 24-54 years with a mean age of 29.9 (SD = 7.14) from Kwangwoon University, Center of Human-centered Interaction for Coexistence (CHIC), and Korea Institute of Science and Technology (KIST). All participants majored in engineering fields such as computer science, robotics, mechanical engineering, and electronic engineering. Before beginning the tests, participants were asked to answer some binary or 5-point Likert questions (i.e., 1 = Strongly disagree to 5 = Strongly agree). Participants reported some experience interacting in virtual environments (e.g., gaming). Most participants were not highly experienced with the VR education system (mean±SD = 2.12±1.6). Two participants had experience using a VR education system.
Point 2: Regarding the Likert-type questionnaire, how was it developed, how were these items defined? Was the 14-item scale validated in advance? How?
Response 2: The background on how we developed the Likert-type questionnaire has been added as follows (page 11, line 358; page 12, line 366):
4.3. Subjective Measures
In this section, user preferences such as the level of immersion, perceived engagement, comfort, and desirability of the IVR-SDO distance education system are examined similar to [14, 26], especially [26], which researched the efficacy of VR in distance team-based learning for students as an engaging platform. To acquire a subjective evaluation on the VR-TBL experiences, we utilized the well-established Likert-type questions. We modified the survey to suitably fit our research and performed 2 pre-tests with the volunteers before the user study to verify that the questionnaire reflects the intent of our research.
Point 3: In the results section, the authors describe the main results of the experimental study, however, a discussion of these results related to the literature review or other related work is missing if possible. Can connections be made between the results of the experimental study and other similar studies?
Response 3: In accordance with the reviewer’s suggestions, we have added the following (page 16, line 428; page 13, line 442):
These experimental results have some similarities with those of the teacher-guided educational VR research [26] on VR field trips. Having a networked education VR setup provides some benefits over the standalone approach of having a teacher’s recording in the VR space. Most notably, by streaming the teacher’s video live, the misunderstandings in communication between the students and the teacher can be resolved on the spot leading to their reduction and higher gains in test scores. Our research also streams the SDO images live to be immersively visualized in the virtual space, peaking the participants’ interest further. Also, similar to the results from the VR-TBL experiences research, the feasibility of having a remote expert teach multiple participants while experiencing co-presence through an education platform was further verified. However, to the question of whether the HMD was comfortable enough to not interfere with learning, a relatively low percentage of participants preferred it because of the weight of the headset. This finding was similarly found in the VR-TBL experiences research and is one of the key issues that must be addressed for long sessions of education in VR.
Author Response File: 
Author Response.docx
Reviewer 2 Report
In this paper, the authors propose an IVR-based distance education system to allow multiple remote users to send, share, and experience Solar Dynamics Observatory images via streaming. The paper describes the system and present a user study. This study is rather limited but fine. This is not a very innovative paper, but it is fine.
Author Response
Response to Reviewer 2 Comments
Point 1: This study is rather limited but fine. This is not a very innovative paper, but it is fine.
Response 1: We would like to thank the reviewers for carefully and thoroughly reading this manuscript and for their thoughtful comments and constructive suggestions, which helped to improve the quality of this manuscript.
As the reviewer suggested, we plan on expanding the current research setup to diversify the possible interactions within the education content and increase the number of participants for a deeper analysis into the effects of immersive remote VR education.
Author Response File: Author Response.docx
Reviewer 3 Report
This paper proposes a distance-based education system for SDO images. It is a relevant problem, considering the constraints associated with the context in which it operates.
The authors have presented an interesting and somewhat novel approach. A particular interesting aspect was the concern with immersion and interaction, which values this work.
A sound evaluation has been performed, with adequate statistical analysis. A higher number of participants would however strengthen the analysis and hence further support the conclusions. Furthermore, a more detailed experience procedure would be appropriate.
Author Response
Response to Reviewer 3 Comments
Point 1: A higher number of participants would however strengthen the analysis and hence further support the conclusions. Furthermore, a more detailed experience procedure would be appropriate. 

Response 1: We would like to thank the reviewers for carefully and thoroughly reading this manuscript and for their thoughtful comments and constructive suggestions, which helped to improve the quality of this manuscript.
As the reviewer suggested, we plan on expanding the current research setup to diversify the possible interactions within the education content and increase the number of participants for a deeper analysis into the effects of immersive remote VR education. Additional explanation into the experimental procedure has been added as follows (page 13, line 379; page 13, line 382):
We architected the experiment to elapse 1 hour per subject a day. Prior to the experiment, each participant was supplied with an overview of what SDO is and the 2 different education methods over 20 minutes. After that, each participant filled out a survey prior to the experiment. The education method using the Hellioviewer for SDO images and IVR-SDO distance education system were randomly assigned to the participants to examine the satisfaction of the proposed system. The order of the two approaches was fully counterbalanced across the 20 participants. The education method using the Helioviewer allows the viewer to observe solar events and SDO images based on the timeline, as shown in Fig. 14. The participants can exchange questions and answers while selecting and observing the SDO images of various spectrums. In testing the IVR-SDO distance education system, two remote students and one expert participated simultaneously while wearing a Vive HMD and earphones and using a controller for hand interaction. From the SDO image server, 10 types of images are streamed to the relay server at 30 fps, and the students and expert accessing the relay server can see the SDO images through the HMD. They can ask questions and receive explanations via voice conversation and feel the presence of other users through the head avatars. After all tests are completed, each participant was asked to answer a sixteen-question questionnaire with a 5-point Likert scale from 1 – Strongly disagree to 5 – Strongly agree.
Author Response File: Author Response.docx
