Dr. Hünig,

I would like to thank you and your co-authors for your significant efforts in addressing the comments and suggestions made by the reviewers to your original manuscript. The manuscript provides a thorough, detailed discussion of the development and performance of the ERICA instrument and will be of interest and use to the aerosol composition measurement community and am happy to accept it for publication pending consideration of a few minor comments (below).

Regards,

Troy Thornberry
Associate Editor

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P1 L13: “aircraft-borne” could be just “airborne”

Two word Latin terms should not be hyphenated (e.g. “in situ” not “in-situ”)

“also called” could be just “or”,

P1 L17: “The same aerosol sample can be sampled with” would be better stated “The same aerosol sample flow is analyzed using”

P2 L7: “like of” should just be “of”, and perhaps say “both refractory and non-refractory”

P2 L9: “method, to quantitatively measure” would be better as “which allows quantitative measurement of”

P2 L 24: The last two sentences starting “Additionally, the TOFMS” and “Furthermore, TOF” seem unnecessary since ERICA does not perform single particle (or size resolved) TD-EI, and other MS can be compact and rugged.

P2 L29: “PALMS…has been operated”

P2 L30: “are for example” could just be “include”

P2 L33: “The TD-EI technique were” should be something like “Instruments utilizing the TD-EI technique have been”

P2 L36: should “adopted” be “adapted” or “implemented”--“for aircraft use”?

P2 L38: the exception being the NASA DC-8 on which HR-TOF-AMS and PALMS have been simultaneously flown since 2013 (DC-3, SEAC4RS, ATom).

P3 L3: “Since, beside” construction is awkward. You could just say here that the limited particle measurement rate” of the LDI is complemented by the higher duty cycle of the simultaneous TD-EI analysis.

P3 L20: “into suitable racks to be operated on other research aircraft such as the NASA DC-8.” What about G-class aircraft such as HALO and HIAPER?

P5 L37: “However, it has been”

P6 L9: “An o-ring around the tube holding the four aperture rings provides the vacuum seal at the pivot point.”

P6 L14: “This design collects a maximum of 70% of the”

P6 L16: “an in-house built” could be “a custom”; “the Trigger Card”

P6 L19: “the TC that measures the particle flight time”

P6 L 27: “The co-emitted light from the laser at”

P6 L 32 (and subsequent occurrences): “Dichroic”

P6 L34: “by reflecting > 99.5% of the 266 nm light while only 12.6% of the light at other wavelengths is reflected.”

P7 L5: “depends on the location of the particle within the laser beam.”

P7 L8: possibly “The maximum repetition rate of the ablation laser, along with factors such as particle losses in the ADL, particle beam divergence, particle and laser beam alignment and the sensitivity of the particle detection units, limits the number of particles analyzed (…), which”

P7 L 13: “ions generated by the laser pulse are accelerated”

P7 L19: RC time constant is only 1/e, so is it possible that the decaying field would affect transmission of charged particles for longer than the 10 ms that is used to determine the 8% potential impact on the TD-EI measurement? I realize that there is significant uncertainty (Fraction charged? Charge? Deflection?) that goes into that estimation.

P8 L9: “orthogonal extraction” is usually used in the context of extracting ions from an ion beam into a TOF. The direction of the aerosol beam is not relevant to the ion extraction in the AMS since the molecules ionized by electron impact are all boiling off of the vaporizer and traveling in a range of directions prior to the pulsed extraction, right?

P9 L1: what is meant by “distracted”? “deflected”?

P9 L10: “all particles would be ablated and ionized assuming a hit rate”

P9 L11: I’m not sure how the refractory composition of the aerosols would make this a conservative estimate except in the case that all of the particles were fully refractory and no signal would have been recorded by the AMS anyway. Otherwise the LAMS results in complete loss of the AMS signal.

P9 L39: perhaps “Determination of efficiencies for optical particle detection and particle mass measurement”

P10 L 28: “which allows combination of the two data sets into one”

P11 L40: does it make sense that the 335 nm AN particle beam has a smaller diameter at PDU2 than PDU1? Converging?

P12 L 30: should “lens” be “ADL”?

P15 L28: what is the transit time of particles through the timing beams relative to the effective time window of the particles within the ablation laser pulse? Are the scattered light signals digitized fast enough to detect the peak and use that for timing?

P22 L7: Don’t all/almost all of the meteoric material-containing particles in the stratosphere also contain sulfuric acid that would be measured by the AMS TD-EI?

A ratio (such as I/rel/ in S5) does not have arbitrary units (a.u.), it is unitless