Short Name: 
HAIS Instrument: 

Manufacturer or Builder:

Recent Projects That Used This Instrument: 
All HIPPO deployments, where it was central to the experiment
Date Acquired: 
January, 2009
Property Tag and/or Serial Number: 
Not Available
Current Location: 

Harvard University

Operational Status: 
Decommissioned ( no longer requestable )
HAIS Instrument
Lead Contact: 
Steve Wofsy, Harvard University
Alternate Contact: 
Britt Stephens
Measurements Provided: 
CO2, CO, CH4, N2O
General Description: 

Note: Effective August 1, 2018, the Quantum Cascade Laser Spectrometer is no longer requestable through the NSF Lower Atmosphere Observing Facilities Deployment Pool.

  • There are two separate components to this instrument, both using quantum-cascade tunable infrared laser differential absorption spectroscopy. One module measures CO2 with an accuracy of 0.1 ppm and a time response of one second. The second measures CO, CH4, and N2O, also with the response time of one second. The two instruments share a single aircraft rack. The instrument uses an infrared tunable quantum cascade laser. Detection is via a compact long-path cell. Two lasers are configured to measure CO, CH4, and N2O, at 1 Hz frequency and with very high precision (better than 0.5, 1.0, and 0.1 ppb Hz-1/2, respectively). A second short-path cell of a new design provides high-precision CO2 measurements (better than 0.1 ppm Hz-1/2 ) using a third QC-laser.
    • (Top left)  Long-path, dual laser, CO_CH4_N2O sensor. Flight hardware with the long-path cell, dual laser assemblies, dual detectors (in one housing), etc., on the shock-mounted optical bench.
    • (Top right)  Assembly showing the purged pressure housing.
    • (Bottom)  CO2 HAIS sensor. Flight hardware of the optical module showing (1) dual detector, (2) dual 4 cm cells, (3) QCL laser assembly.


The QCLS in a GV rack as installed for flight.


Measurement Characteristics: 
  • Overall estimate of uncertainty: CO2: 0.1ppm
  • Response time: 1s
  • Precision: better than 0.1ppm, 0.5, 1.0, and 0.1ppb Hz-1/2 for, respectively, CO2, CO, CH4, N2O
Calibration Methods: 

in-flight calibration uses standards carried in gas cylinders

Time series of QCLS measurements of CO2 (left) and CO (right) compared to "classic" measurements (from the Harvard OMS instrument) and to the NCAR CO instrument. Also shown are the corresponding measurements of N2O and CH4. The sawtooth gray lines show the measurement altitude in reference to the scales on the right sides of the graphs.