RAF

In-Cloud Air Temperature Radiometer

Measures air temperature by comparing air radiance in the carbon dioxide 4.3 µm band with a reference blackbody at near-ambient temperature. It is generally unaffected by wetting caused by passes through wet clouds so the main use is anticipated to be in clouds and immediately upon leaving clouds when the Rosemount sensors are affected by wetting or evaporation.

Ultraviolet absorption hygrometer

The UV Hygrometer measures the absorption by water vapor of vacuum-ultraviolet light at the Lyman-alpha wavelength of atomic hydrogen (121.6 nm). Air from outside the aircraft is brought to the absorption cell by a forward facing open-ended cone inlet (SCAI inlet) and exhausted through a scarf tube. The shortest possible absorption path-length, 2.4 mm, is used for high water vapor mixing ratio conditions, 2-15 g/kg.

Laser Air Motion Sensor (LAMS)

  • The LAMS measures airspeed in a region of undisturbed airflow via the Doppler shift in the frequency of laser light returned from a laser beam focused ahead of the aircraft. The coaxial laser system uses optical heterodyning to detect the Doppler shift in light backscattered from atmospheric aerosols.
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HIAPER Aerosol Spectrometer Probe, Optical Particle Counter

****** The OPC is not currently requestable ******

The OPC has optics from a PCASP (original probe by PMS), electronics and data interface from DMT, and a flow system designed by RAF.  Instrument is similar to DMT's PCASP-X2.  It is a rack-mount instrument with internal air pump, and for sampling requires an inlet and tubing. Particle detection and sizing are based on laser light scattering, with pulse amplitude determined with two gain stages to cover the large dynamic range.

Instrument Exhaust Gas Dump Pressure

Long rigid tubes 5 cm dia are installed on left and right sides of the fuselage cabin. These tubes have collection fittings at several locations where air sample instruments can vent their exhaust. The tubes vent to the belly of the aircraft and have a skarf tube cut that provides a pressure reduction. Pressure sensors are located near the vent locations.

 

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