Short Name: 
VCSEL
HAIS Instrument: 
Yes
Recent Projects That Used This Instrument: 
All GV projects since PACDEX, except Icebridge and Sprite-II

Manufacturer or Builder:

Deployments: 
CONTRAST
DEEPWAVE
Date Acquired: 
January, 2008
Property Tag and/or Serial Number: 
11640
Current Location: 
NCAR
Operational Status: 
requestable, ready for deployment
Lead Contact: 
Stuart Beaton
Alternate Contact: 
Matt Hayman
Measurements Provided: 
Water vapor concentration and related derived values (mixing ratio, dew point, etc.)
Typical Sampling Rates: 
25 samples per second
General Description: 

The VCSEL hygrometer employs tunable diode laser absorption spectroscopy to determine the water vapor number density over a dew-point range of -90 to +30º C. It reports the water vapor number density and approximate dew-point at 25 samples per second. It is mounted on a GV aperture plate, weighs 3.2 kg and draws less than 20W from 120 VAC, 60 Hz.

The hygrometer operates in two absorption modes on two wavelengths: wavelength modulation on a weak absorption line (1853.3 nm, used for high mixing ratio conditions), direct absorption on a strong line (1854.0 nm for moderately low mixing ratios), and wavelength modulation on the strong line (for low mixing ratios). The sample volume is an open-path Herriott cell, giving an absorption length of 375 cm in a volume approximately 20 cm long and 2 cm diameter.

Measurement Characteristics: 

5% uncertainty from lower troposphere to lower stratosphere.

Calibration Methods: 

Defined by spectroscopic parameters and reference spectrum stored in EEPROM. Refined with dew-point generator, slush baths, critical orofice mixing.

History of Significant Changes: 

8/2010: Replaced gold mirrors with more rugged dielectric mirrors.

Data shown below is the one second housekeeping data (beginning with SWS), the 25 samples per second mixing ratio and dew point data, and an every-5-minute spectrum (SPEC). Lines are terminated with CR/NL.

 

The 25 s/s data record consists of the number density (#/cc), laser intensity, approximate dew point (°C), and # of spectral scans averaged, normally 60. SWS 1199 544 295.9 628.9 9430 9431 408 D 0.0794 2000 30 4095 52 0 7.0 2718 4.13E+15 1788 -41.16 60
3.67E+15 2804 -42.28 60
3.67E+15 2757 -42.27 60
3.68E+15 2756 -42.25 60
3.68E+15 2757 -42.26 60
3.67E+15 2757 -42.27 60
3.67E+15 2757 -42.27 60
3.68E+15 2757 -42.26 60
3.67E+15 2757 -42.27 60
3.66E+15 2757 -42.30 60
3.67E+15 2757 -42.29 60
3.66E+15 2757 -42.29 60
3.67E+15 2756 -42.28 60
3.66E+15 2758 -42.30 60
3.65E+15 2757 -42.33 60
3.66E+15 2757 -42.30 60
3.67E+15 2757 -42.28 60
3.67E+15 2756 -42.29 60
3.66E+15 2757 -42.31 60
3.67E+15 2758 -42.29 60
3.67E+15 2756 -42.28 60
3.67E+15 2756 -42.27 60
3.67E+15 2757 -42.27 60
3.62E+15 2756 -42.40 1
SWS 1200 544 295.9 628.9 9430 9431 408 D 0.0794 2000 30 4095 52 0 7.0 2718
SPEC -1.63E-01 -1.63E-01 -1.63E-01 -1.63E-01 -1.63E-01 -1.63E-01 -1.18E-01 -8.84E-02 -5.56E-02 -1.37E-06 7.99E-02 1.55E-01 2.40E-01 2.96E-01 3.17E-01 3.30E-01 3.38E-01 3.54E-01 3.66E-01 4.03E-01 4.32E-01 4.55E-01 4.96E-01 5.32E-01 5.49E-01 5.83E-01 6.30E-01 6.87E-01 7.37E-01 7.84E-01 8.46E-01 8.96E-01 9.63E-01 1.03E+00 1.11E+00 1.20E+00 1.29E+00 1.39E+00 1.47E+00 1.59E+00 1.70E+00 1.82E+00 1.95E+00 2.09E+00 2.23E+00 2.35E+00 2.49E+00 2.64E+00 2.78E+00 2.92E+00 3.05E+00 3.18E+00 3.29E+00 3.36E+00 3.43E+00 3.48E+00 3.51E+00 3.50E+00 3.48E+00 3.44E+00 3.37E+00 3.29E+00 3.15E+00 3.03E+00 2.89E+00 2.76E+00 2.61E+00 2.46E+00 2.31E+00 2.17E+00 2.02E+00 1.88E+00 1.73E+00 1.59E+00 1.44E+00 1.32E+00 1.20E+00 1.10E+00 9.97E-01 9.06E-01 8.15E-01 7.09E-01 6.18E-01 5.43E-01 4.61E-01 4.01E-01 3.41E-01 2.80E-01 2.03E-01 1.50E-01 1.05E-01 5.29E-02 4.26E-03 -2.84E-02 -5.13E-02 -1.15E-01 -1.60E-01 -1.97E-01 3.83E+15 1788 -41.88 60
3.66E+15 2803 -42.31 60
3.67E+15 2758 -42.27 60
3.68E+15 2757 -42.25 60
3.68E+15 2755 -42.26 60
3.66E+15 2757 -42.31 60
3.65E+15 2756 -42.32 60
3.66E+15 2757 -42.31 60
3.66E+15 2757 -42.31 60
3.66E+15 2756 -42.30 60
3.68E+15 2755 -42.26 60
3.67E+15 2754 -42.29 60
3.66E+15 2756 -42.30 60
3.67E+15 2755 -42.27 60
3.67E+15 2756 -42.29 60
3.67E+15 2758 -42.28 60
3.66E+15 2758 -42.31 60
3.65E+15 2758 -42.34 60
3.64E+15 2759 -42.35 60
3.66E+15 2757 -42.30 60
3.65E+15 2757 -42.32 60
3.65E+15 2758 -42.33 60
3.64E+15 2758 -42.35 60
3.60E+15 2757 -42.46 1
SWS 1201 544 295.9 628.9 9430 9431 408 D 0.0794 2000 30 4095 52 0 7.0 2718