The manuscript describes the promising development of a low-cost, fast-response tunable-diode laser spectrometer for measuring water vapor in the atmospheric boundary layer. As the instruments hard and the software design is based on readily available components, lightweight, and energy-efficient it can be easily reproduced and exhibits a broad spectrum of potential atmospheric measurement applications. The laboratory calibration and first atmospheric measurements show a high accuracy and precision of 10 ppm at 10Hz allowing for sampling with high spatial and temporal resolution.

General:

• The consistency of naming should be improved throughout the manuscript. Some names are changed multiple times as an example: Teensy =   Teensy 4.1 = data collection microcontroller = receiver. Also introduced acronyms should be used or left out. More consistency here would be very helpful.
• The quality of language/sentence syntax should be improved. Many typos, slips of the pen, and complicated/convoluted sentences.
• The plotting ticks should be changed using to a more standard style as they are confusing that way. E.g.: Fig 5, yaxis highest tick should be 30, above the axis a common coefficient with 1x10^-3
• Also cross check references if missing and use correct citation style: Textual citation XXX et al. (YYYY) vs. parenthetical citations (XXX etl al. YYYY)

2.1 Hardware Description

• The captions of Fig.1 to Fig. 3 should be extended to be self-explanatory and not reference to the text.
  
  For example: Fig 1, please explain the different components shown: are drive input and TEC input circuits by themselves, how does the TIA look, are the laser driver and data collection unit the two Teensy microcontrollers…

• L 103: The laser wavelength is tuned via temperature?
• L 105: add ± before 0.002 K
• L 127: adapt trigger pulse direction in Fig 1. From driver to data collection if the text is correct
• L129: After 5V reference to figure
• L 141 – 146: Please clarify: Was the laser collimated or divergent? How much bigger is the laser beamwidth compared to the InGaAs sensor active area? Have there been any tests regarding vibrations? (Even collimated laser beams show a distinct Gaussian profile which could induce signal variations upon vibration)
• L 149: Syntax wrong or double sentence

2.2 Spectral Processing

• L 163: please cross check values on where the offset/drift is determined 30 & 20 points vs. 10 point in fig 4 caption.
• L 165 – 169: This part requires more clarification on how to convert scan steps into wavelength.
• L 170: What do you want to say with the “[..] are then placed in an array?
• Fig4 (b) Unit should be wavenumber

3. Results:

• Fig 5: Does the x-axis represent values measured by the Picarro or converted values from the TDLS?
  
  Please also state the lin-regress function parameters (slope, intercept, ^r2) or a plot of the converted H2O-ppm from TDLS over H2O-ppm measured by the Picarro together with a 1:1 line and respective regression slope. Similar as for Figure 8 (b)

• L 216 – 220: This part needs more clarification. Was a different InGaAs sensor used for the calibration of the instrument than the actual measurement? That could yield a different conversion coefficient.
• L 239: Wu et al 2015 citation not present in references
• Fig8 (a). Please convert the x-axis to actual time in UTC
•  L 278: Doesn't the averaging over 30s smooth all variation on a spatial scale of 1.5m? Hence I am not surprised that that values align even the locations had a 1.5m separation.

Some Typos:

• L 104: remove dot after “([…], MT)”
• L 111: add quotes “ after receiver
• L 122: resister -> resistor
• L 209: remove dot after “(black points)”
• L 256: lowercase a before 25-m long
• L 298: Remove dot after power
• L 320: mission word(s) after water
• L 325: Either tested or powered
• L 333: remove with before TEC
• L 337 delete “configuring for use”
• L 342: ABL was already introduced in the introduction