En-SCI - Cryogenic Frost Point Hygrometer

• To study the upper and lower troposhpere.
• Measure the amount of water vapor inside ice clouds
• Dehydration studies (particularly in the tropical upper troposphere)
• Validation of satellite measurements and radiosonde humidity sensors

• Measure water vapor at the parts-per-million level
• Avoid the costs associated with aircraft-mounted instruments
• Simple operation
• Lightweight design with minimal power requirements
• Can be launched with small balloons
• Perform accurate measurements during ascent as well as descent
• Software included for easy monitoring of the CFH unit
• Compatible with EN-SCI ECC Ozonesondes

The CFH operates by maintaining a small mirror at the precise temperature necessary to generate a thin, constant layer of condesate on the mirror. When this layer exists, the mirror temperature is the same as the ambient frost or dew point temperature.

An LED emits light that is reflected off the mirror, and a photodetector senses this reflected light, which varies with the amount of frost. The photodetector signal is then used to adjust the mirror temperature. The mirror is heated with a heater coil and cooled with cryogenic liquid. These mechanisms allow the mirror to be heated and cooled quickly so that its temperature reflects the current frost or dew point.

• Measured Parameters Ambient Frost Point
• Derived Parameters Relative Humidity, Mixing Ration
• Technique Temperature-controlled chilled mirror
• Uncertainty Measurement 4% in tropical lower troposphere
• 10% in middle stratosphere
• 9% in tropopause
• Altitude Range 0 - 25 km (all climates)
• Weight < 400 g (without coolant)
• Instrument Dimensions 7.6 cm x 7.6 cm x 13.3 cm
• Dimensions (in Flight Box) ~12" W x 12" D x 12" H (~39cm x 39cm x 39cm)