The authors describe a lightweight UAV system for measuring organic aerosol particles and present first vertical measurements from a rural area in southern Germany. The paper is well written and fits within the scope of AMT. However, there are some problems that need to be corrected before the manuscript can be published.

Major comments

Introduction

Why does the paper only mention vertical profile measurements? UAVs are particularly suited for horizontal measurements, which supply the benefit of scanning areas and understanding emission sources (see literature).

Experimental procedures

Have you studied the turbulence of the rotor? Most groups working on aerosol sampling with UAVs use smog experiments to make turbulence visible. The position of your setup is given in the appendix. However, the pictures don't show the dimensions. Please add these dimensions to the pictures or provide a sketch with the dimensions. This is especially important for the distance between the instrument and the rotors. Since the results are very impressive and the effect of turbulence can obviously be neglected, the question is why. After all, the body of the UAV acts as a kind of shield and allows a shielding flow around the UAV? A colored smog test would show this.

Figure 1 shows a schematic of the filter holder. Again, the dimensions are missing. How long is the filter holder? What is the length and diameter of the pump? What is the diameter of the pump inlet? What is the distance from the filter to the pump inlet?

Have you determined the deposition characteristics of your filter holder? What are the diameters of the particles (size range) being filtered? Have you determined the total number of particles you are filtering per volume? What are the particle concentrations in number and mass?

Other parameters that are missing are the down wash distribution, the rotor speed, and the weight of the sampling unit.

Can you open and close the inlet to your filter assembly or can you turn the pump on and off during the flight to ensure that you are sampling only from the appropriate altitude?

Electronic circuits and the schematic structure of the measuring unit are also missing. If software was used for the control system, this must also be specified in the appendix.

Results and Conclusions

The manuscript presents an impressive proof of concept. The results are robust and in line with expectations for the measurement situation. However, more information on the setup is needed to evaluate the errors.

Minor comment

“UAV” is the common term. You could use "UAV" instead of "drone".

In the manuscript, authors are presenting interesting results for atmospheric organic aerosols sampled with lightweight filtration system in the aerial drone. The manuscript is mostly well done and written, although some minor inaccuracies exist and need to be fixed.

1. Page 3, line 65: What was the material used for printing the filter holder?
2. Page 3, line 83: Generally the best sampling point is under the body of the drone/sampling unit (less affected by the flow caused by propellers)?
3. Page 4, lines 96-99: Total volume of extraction solutions will be 3mL+1.5mL+1.5mL. How this (6 mL together) can be transferred to 1.5mL vial? Rewrite to clarify what was done and how. Also give the volume to what the supernatant was concentrated under N₂
4. Page 4, lines 105-110: Generally, both A and B eluent components should contain 0.04% formic acid. Then its amount (and eluent pH) would stay constant. Now the pH will change during the concentration gradient. Also you should report what was the pH. For acidic compounds with negative ESI, basic conditions are normally used for efficient ionization and good sensitivity. Now the conditions used are more suitable for positive ESI. You could have tried to modify the eluent and pH used for example adding ammonium acetate or ammonium fluoride instead of formic acid. If the chromatography is not good with these, then this modification could be done post column with ESI nebulizing liquid.
5. Page 4, lines 116-117: The voltage regulator would be good to include in the future (and maybe mention this in the conclusions).
6. Figure 7, figure legend: 10:35 is as far from the noon as is 13:35. You could talk about late morning (10:35am), early afternoon (13.35pm) and late afternoon (4:30pm)? Also for some cases you have 24h system (13:35 pm) and some 12 h system (4:30 pm), so be consistent. Fix these throughout the whole manuscript (at least in Figure 6 there is 13:35 pm).

See attached .pdf