RC1:

“This paper on mass spectrometric measurements of heavy ions in the meteor ablation zone adds considerably to the little that is known. On of the authors discovered these many years ago and this builds on that legacy. The paper is well written and applicable to a variety of atmospheric questions and should be published after minor revision. I have two points that will improve the paper slightly and a few grammar type corrections.

The altitude vs mass graphs include a lot of dark blue points. These seem to be ignored in some of the description. I am guessing because they are thought to be noise in the multiplier but I didn’t see this description. The authors should be addressed by a short description of what is signal and what is noise.

We will include a more detailed explanation regarding the background.

Background noise is usually composed of dark noise in the multiplier, penetrating radiation and UV-photons. In our data, we see the noise is increasing with altitude. Dark noise should be constant and is usually in the range of some counts per minute, thus we ignored this effect. Further is the multiplier placed within the cryopump and within the rocket structure summing to a shielding of several mm of steel, copper and aluminum, which allows only cosmic rays to penetrate to the multiplier. This form of background noise is also in the range of only a few counts per minute and we thus assume that scattered UV photons are the most likely cause of the background noise.

These types of particles have been proposed to be part of a cycle that leads to meteor radio afterglows. A sentence or so mentioning this important is probably appropriate. Association between Meteor Radio Afterglows and Optical Persistent Trains, K.S. Obenberger, J.M. Holmes, S.G. Ard, J., Dowell,, N.S. Shuman, G.B. Taylor,  S.S. Varghese, and A.A. Viggiano J. Geophys. Res. 125 10.1029/2020JA028053 (Sep 2020).

ADDED

Page 5. Define PFTBA

ADDED: (Perfluorotributylamine or FC-43)

Page 5, Table 2, RF Voltage maximum, not RF voltage since it is variable.

ADDED: max. RF voltage

Page 9, beginning of rocket launches. I don’t know what a mesospheric winter echo is, so it should be defined.

ADDED: The campaign PMWE aimed to study polar mesospheric winter echoes (PMWE) which are VHF radar echoes during the winter month at high latitudes. It was theorized that negatively charged MSPs may be involved in the creation of PMWE. As a result of the first flight, Staszak et al. (2021) could show that PMWE are ultimately caused by turbulence and that MSP only enhance the radar echoes.

Page 17, line 19 line 247, smoother not more smooth

CHANGED: smoother

First paragraph of summary. Divers is twice mentioned – should be diverse.”

CHANGED: diverse

RC2:

“This paper is a comprehensive presentation and analysis of recent observations of positive and negative ion mass spectra in the polar D and E region using a new cryogenic quadrupole mass filter based on a former, established design. The main objective are in situ studies of the composition of meteoric smoke particles (MSP). The authors suggest the detection of several positive and negative species, mostly containing Fe (iron), in line with models and some previous observations. 

The results are based on only two flights, including some inconsistent results between the flights. More flights and further instrumental improvements should be pursued to confirm the composition altitude structure. Nevertheless, the paper is an important new contribution continuing several decades of D region ion and heavy ion measurements. 

In this context I recommend to add Chesworth, E.T. and Hale, L.C. (1974), Ice particulates in the mesosphere. Geophys. Res. Lett., 1: 347-350. https://doi.org/10.1029/GL001i008p00347  as an example and review of earlier work on mesospheric heavy ions (not only icy aerosols), even though these were not all mass spectrometer measurements. “

ADDED

“I recommend publication in its present form after some minor fixes and clarifications.   

The paper is well written, however, there are some typos and other errors. I recommend using a good spell and grammar checker.  A few sentences were unclear (for me or a general reader); they can be rewritten to improve the general flow and understanding. “ 

L.3. frame —> framework CHANGED

L.3. PMWE introduce acronym ADDED

L.4. IAP introduce acronym ADDED

L.5 allow —> allowed CHANGED

L.6. divers —> diverse CHANGED

“where is the significant result? key points?  This could be made stronger in the abstract. “

We will make this more clear

L.20. an (duplicate) DELETED

L.20. DLR introduce acronym ADDED

L.20. MPI introduce acronym ADDED

L.21. LMU introduce acronym ADDED

L.22. 1980s CHANGED

L.25. ions, CHANGED

L.28. the instrument in detail CHANGED

L.88. usec —> µsec CHANGED all occurrences

L.100. the mass scan increases (no comma) CHANGED

L.100. negative steps in the count rate: unclear, what does this mean? the count rate drops? CHANGED

Indeed the count rate drops for a negative step

L.107. PFTBA introduce acronym ADDED

L.109.  ROMARA-1, but to … extent.  CHANGED

L.115. what is a “cone distribution”? 

Particles in the 3D simulation start from a point towards the instrument. They have a distribution of direction that is bound by a cone with an opening angle 2 times the cone angle.

L.121. capitalize Mode A, Mode B CHANGED all occurrences

L.145. mode —> modes CHANGED

L.171. unclear: what negative measurement slots?  I think the white gaps in Fig. 6, but can be clearer CHANGED

L.181. to explain the NO+/O2+ peak; what was the total plasma density in R-1 and R-2, from other instruments? 

Our measurements usually use the electron density to calibrate an ion density. We included the electron density for R1 in Fig.14. Other data is not available and a crude calculation from the count rate would simply be too uncertain to publish as the sensitivity of our instrument is not well known. While we could indulge in this very interesting topic it would defocus the paper.

L.191. too sensitive for the prevailing …   what does this mean?  Need some kind of transition to the explanations that follow.

The negative measuring mode was too sensitive for the present particle concentration during the flight.

L.191. where is the cap ejection in Fig. 8?

Here I made a mistake. The figure showed plots where I experimented with an interpolating fill of the slots and somehow these versions entered the preprint version. This affected Figures 6 and 8. The figures are corrected and now the sudden increase of counts at about m/z 500 in the very first spectrum is more clear. The very first spectrum at the bottom of the plot.

L.193. how can one see the payload spin at m/z 460 in Fig. 8?

The countrate is modulated by the payload spin with a period of about Δ m/z 460 (0,27s). This is visible between 60 and 75 km as a wavy structure. We used the mass per charge to describe the period as it directly translates from a time (mass scan), but the plot only shows mass per charge. We will clarify this in the revised version of the paper.

L.201. paralyzed = saturated? 

A paralyzing channel electron multiplier detector is characterized by a dropping or even disappearing count rate as compared to a saturating detector that simply gives its maximum count rate. As we mentioned in the following sentence, the count rate plateau was much below the maximum count rate of the counting system. ADDED reference (Wuest et al. 2007)

L.213. why is this unexpected?

We would have expected that based on the ROMARA-1 flight showing counts for negative ions below m/z 100. We will clarify in the text.

L.238. It might be helpful to reproduce a model of expected ion species from MSP here, so that the reader has a reference

We refrained from including model results in the paper since we consider this to be out of scope for this measurement report. We have chosen the format of the ACP measurement report to make our measurements quickly available to all modelling groups in this field.

L.242. Despite that … CHANGED

L.259. To begin with, (comma)  CHANGED

L.268. “high probability” according to the measurements (interpretations?) by Hervig  CHANGED

L.273. At this time …  this sentence is unclear, should be rewritten, this goes back to the explanation of spin signal in the spectra.

We will make that correlation more clear. As a mass scan takes a certain time, time correlates to mass. For R1 this is linear and for R2 it is logarithmic. However, a full mass scan in R2 needs about 600 ms and the spin rate is 277 ms.

L.294. diverse —> ambiguous?  CHANGED

L.296. ca. —> about (circa is in English c., not ca.)  CHANGED to “about” as the circa thing is internationally not that obvious

L.298. diverse  CHANGED

L.304. —> his proposed “magnetite, …” CHANGED

L.305. or deny —> nor reject  CHANGED

L.308. MLT region (no hyphen)  CHANGED

L.311.  How quantitative are these total charged particle profiles?  As mentioned above a comparison with an absolute electron density or positive ion density profile measured on the same payload would be helpful. 

We included the electron density of ROMARA-1 from Staszak 2021 into Fig. 14. Generally the ion density is supposed to be equal to the electron density (quasi-neutral atmosphere). As the payload travels through the atmosphere at supersonic speeds the shock in front of the instrument influences the amount of particles hitting the cone drastically and thus simple relationship between cone current and ion density is difficult to establish.

L.330. add some commas or semicolons in this listing of authors CHANGED

RC3:

“This manuscript reports the in-situ measurements of charged nanoparticles/heavy ions in the mesosphere/ lower thermosphere during two rocket flights. These are important results for research into the upper atmosphere/ionosphere because there are only few in-situ measurements of this kind. The measurements are presented appropriately. However, an evaluation of the presented measurements regarding the scientific discussion in the field is missing from the manuscript. The authors ignore theoretical work and model calculations from recent years that deal with the size and distribution of meteoric smoke particles. The connection with meteors should also be presented - albeit briefly.

The reader is left with the question how the presented work connects to the current knowledge in the field.”

Our “measurement report” directly refers and builds upon significant publications in the field, which allowed us to interpret our data.

“The authors seem to refer to the “meteor smoke” as discussed in the literature, but do not adequately describe what is meant by this (One small but confusing thing is that other works use the term “meteoric smoke.”). “

We elaborate this further and include a description of MSP charging.

“Furthermore, the terms “clusters” and “heavy ions” are used.”

We will make this more clear by defining “heavy ions” as ions m/z >100 that potentially build clusters of these ions.

“A comparison of the obtained results with the particle sizes and masses used by other authors is missing. This is applicable at least for the high mass numbers and it would allow the reader to assess the results in comparison to other works.“

This was done in Stude et al. 2020, we will point that out for the high mass numbers, e.g. m/z5000 ~ 0.8 – 1.0 nm

“The title of the manuscript seems to imply that "meteor smoke particles" are heavy ions. Water clusters are also mentioned. How are all these components connected?”

If MSPs are ionized, one could see them as a kind of heavy ion or cluster ion. Water cluster ions exists below about 85 km and are positively charged. These could be misinterpreted as MSPs in a mass spectrometer with insufficient mass resolution. Albeit at these altitudes, MSPs should be negatively charged and heavier. See Johannessen(1972) and Reid(1977).

“Theoretical works on meteoric smoke formation often start from an initial size of 0.2 nm: based on the presented measurement, can you support this assumption?”

In Stude et al.(2020) we tried to establish a connection between the communities using size and mass spectrometry using mass. If one talks about particles with sizes above say, 1 nm, than the notion of molecular mass becomes less meaningful given the large numbers. Most models use a spherical assumption and a material density to achieve a number density. E.g. 2g cm-3 for a radius of 1 nm equals to 5000 u.

Thus there is a difference between a macroscopic view on the problem e.g. for a global model of number densities and a microscopic view on the composition of particles, where mass is applicable.

From Stude et al. 2020 (Fig.1) we would assume that 0.2 nm particles have a mass <100 u. Other sources give for example 0.2-0.3 nm for a water molecule. It makes sense to include these sizes in a model given the most probable molecules we found are in the range of 200 u. However, molecule sizes are maybe a misleading property in the field of mass spectrometry.

“How do the results link to other parameters measured during the same rocket flights? And finally, what does all this have to do with PMWE?”

We include the electron density from ROMARA-1 flight in the revised paper but do not have this data from ROMARA-2. This paper focuses on the ion composition and we have choosen the format of the ACP measurement report to make our measurements quickly available to the science community in this field. Other measurements from the flights besides the electron density are not linked to the ion composition.

It was theorized that negatively charged MSPs may be involved in the creation of PMWE. But as already the first flight showed, MSPs are not the ultimate cause of the phenomenon and our data do not correlate to the echo altitudes. Staszak et al. (2021) could show that PMWE are ultimately caused by turbulence and MSPs only enhance the radar echoes.

The manuscript needs major revision before being published in ACM.

Minor revisions and language corrections are also recommended. Points for minor revisions were also given already by other reviewers, some are given below:

line 1: we present data from “rocket” flights ADDED

line 10: m/z not defined in abstract, not defined when first used in text ADDED

line 14: ablation takes place over a height interval and the forming particles are carried in the atmosphere – please expand and provide references

We will expand and include appropriate references

line 20/21: write out or define LMU, IAP, DLR CHANGED

line 39: give reference for existence of water clusters ADDED Johannessen et al., 1972

section 2.1: table 2 is not mentioned in the text – please also check whether all figures and tables are refered to in the text ADDED tab2 and fig 9

line 96: rephrase sentence: “The result is a spectrum…” CHANGED

“data access: there is a link given for the data, but access does not work - possibly because of a lack of documentation”

The links to our data work as tested at the time of upload and again after the reviewers comments, the required information to use the data is included in the files.