Global Monitoring and Characterization of Infrasound Signatures by Large Fireballs
Round 1
Reviewer 1 Report
The authors discuss the use of the International Monitoring System of infrasound measurement station network deployed in the framework of the Comprehensive Nuclear-Test-Ban Treaty for detecting large bodies (meteorites) entering the atmosphere. The authors combine direction of arrival triangulation with time of flight trilateration to assess the position of the body entering the atmosphere. Furthermore, by modeling the acoustic propagation conditions depending on the atmospheric layering, they assess the power dissipated by the body entering the atmosphere and generally find a 60% lower yield than data published by NASA JPL.
While my background is closer to electromagnetic phenomena location than acoustic, I found the same rationale in the analysis in which I did not identify any flaw. This work follows the intensive use of CTBT infrasound network for geophysical use by the French Nuclear Agency (CEA) staff which is properly referred to. Amongst the minor comments:
multiple references to social media communication for assessing the position and trajectory are mentioned in the text but never used for assessing the validity of the trajectory deduced from infrasound. Of course the poorly populated regions of the Bering strait would be poorly suited for such an assessment but the russian meteorite has been widely reported in such media, the analysis would be interesting. the authors conclude that their yield analysis leads to 60% lower power than NASA published results, but the way NASA addresses the dissipated power is unknown (p.11 l/ 374: "It has to be mentioned that there is no detailed information available on NASA’s CNEOS data,neither on the detection method or calibration nor on the accuracy and completeness of the data. ") This is of course a major limitation and it can be hoped that the processing scheme will be revealed following this publication.
Trivial: p.9 l.300 : "ehereas" is incorrect
Author Response
Dear Reviewer 1,
thank you for taking the time and interest to deliver this constructive review of our manuscript and for estimating our work rational and flawless for publication in MDPI Atmosphere. We carefully studied your comments and provide replies below.
Thank you again and best regards,
Christoph Pilger and co-authors
Reply to Reviewer 1 comments:
- multiple references to social media communication for assessing the position and trajectory are mentioned in the text but never used for assessing the validity of the trajectory deduced from infrasound. Of course the poorly populated regions of the Bering strait would be poorly suited for such an assessment but the russian meteorite has been widely reported in such media, the analysis would be interesting.
We agree, this would be a very interesting result! It was done e.g. for the Chelyabinsk fireball in Brown et al. (2013) but would go beyond the scope of this work. They focused on one fireball only. Social media is used in the course of the NEMO project to stay informed and find fast information, less for accurate scientific information. Uploaded videos are usually without precise position (and direction for dash cams) information and without information about the technical details of the camera. This makes an analysis very complex. The accuracy of trajectories computed from witness reports are uncertain, too, as can be seen e.g. for this fireball https://www.amsmeteors.org/2019/09/daytime-fireball-over-north-sea-on-sept-12th-2019/. They also depend a lot on the witnesses' position in relation to the fireball trajectory. For fireballs which are detected by e.g. a fireball network, there is more scientific information available. A very interesting point for future work.
- the authors conclude that their yield analysis leads to 60% lower power than NASA published results, but the way NASA addresses the dissipated power is unknown (p.11 l/ 374: "It has to be mentioned that there is no detailed information available on NASA’s CNEOS data, neither on the detection method or calibration nor on the accuracy and completeness of the data. ") This is of course a major limitation and it can be hoped that the processing scheme will be revealed following this publication.
We have the same opinion and hope that further information will be made available soon, following this study and supporting future work.
- Trivial: p.9 l.300 : "ehereas" is incorrect
This was corrected in the reviewed manuscript version uploaded with this review
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript on " Global Monitoring and Characterization of Infrasound Signatures by Large Fireballs" by Christoph Pilger et al. has quit enough description about a comprehensive study of ten large fireball events of the years 2018 and 2019 which highlighted their detection and characterization by using global infrasound arrays of the International Monitoring System (IMS) of the Comprehensive Nuclear‐Test‐Ban Treaty (CTBT). They studied by focusing on the event analysis of representative ten fireballs to estimate their respective location, yield, trajectory, and entry behavior. Signal characteristics derived by PMCC method were utilized and compared with the events determined by a NASA reference database. In addition, application of atmospheric propagation modeling allowed to draw conclusions about infrasound-based detection capability, localization accuracy, yield estimation, and source characterization efficiently. Their fireball case study clearly showed the characterization of four different meteoroid‐related source processes all observed at one nearby infrasound array. A final case study regarding the Bering Sea fireball quantified the global infrasound detection capability for an exceptionally large fireball event. In these concerns, this paper is well coordinated and has a detail description in each chapter/section, therefore, it is recommended this paper could be published in the present form slightly after considering the following arising one question.
Arising Questions and comments:
Authors compared and discussed about the difference between the energy values listed in Table 1 (by this work) with the ones published in the fireball database from the CNEOS. It was also mentioned by authors that there was no detailed information available on NASA’s CNEOS data, neither on the detection method or calibration nor on the accuracy and completeness of the data. Are there any ideas about the practical solution for reducing the data from NASA’s CNEOS in sufficiently satisfied contents? In that case, are there any additional expectational results revealed by difference in these energy values?
Author Response
Dear Reviewer 2,
thank you for taking the time and interest to deliver this constructive review of our manuscript and for estimating it being a well coordinated study and detailed description for publication in MDPI Atmosphere. A reply to your review comment is provided below.
Thank you again and best regards
Christoph Pilger and co-authors
Reply to Reviewer 2 comment:
- Authors compared and discussed about the difference between the energy values listed in Table 1 (by this work) with the ones published in the fireball database from the CNEOS. It was also mentioned by authors that there was no detailed information available on NASA’s CNEOS data, neither on the detection method or calibration nor on the accuracy and completeness of the data. Are there any ideas about the practical solution for reducing the data from NASA’s CNEOS in sufficiently satisfied contents? In that case, are there any additional expectational results revealed by difference in these energy values?
Unfortunately, there is no practical solution for this as far as we know. There is not even information available about the satellites collecting the data. We can only hope that the processing scheme will be revealed soon.
