FAAM has 2 Cloud Imaging Probes which are wing mounted single particle optical array probes with complimentary sensors for air temperature, relative humidity, air speed (pitot tube) and liquid water content. Manufactured by Droplet Measurement Technologies, the CIPs' fulfil the core data-set requirement for particle sizes over the range of 15μm to 930μm at 15μm resolution (CIP15) and 100μm to 6200μm at 100μm resolution (CIP100). The CIPs' provide:

Both CIPs' are fitted with anti-shatter Korolev tips which minimise the effects of particle shattering which can contaminate the sample area. The CIP15 tips have a short arm-width length of 40mm, and the CIP100 has a longer arm-width length of 70mm.

System components:

The basic components and theory of operation for the CIPs' is as follows:

• An incident laser beam is focused on particles within the size range of the instrument, which are optically magnified onto a 200 micron pitch, 64 element diode array.

• A diode laser produces an oval 50mW beam which illuminates the diode array. Whenever a particle passes through the beam, a shadow is generated and imaged onto the diode array. This photodiode information is stored by onboard digital electronics at TAS frequency (where TAS is determined using the CIP pitot tube).
• Each sample of the 64 elements is a slice, where up to 62 slices compose a particle image (end-diodes 1 and 64 are rejected).
• The digital signal processor sizes the particles by slice count and stores the cumulative number of particles of each size.
• It also compresses the image data using run-length encoding. This synchronous data is sent to the host computer for real-time display by PADS software.
• Asynchronous image data is transmitted to the host computer whenever the compressed data fills a 4096 byte buffer, the host computer then uncompressed a portion of this data for image display, and stores the entire compressed information to disc.

LWC

• The LWC hotwire system is housed between the CIP sampling arms, and is only ever powered when the aircraft is airborne to avoid over heating the element.

• The sensor’s temperature is maintained at 125degC via a digitally control variable duty-cycle current pulse.
• The more liquid water present, the greater the current required to maintain the fixed 125DegC. Thus the liquid water content is determined as a function of current through the device, minus the TAS component.

Instrument Specifications:

Size range: CIP15: 15μm to 930μm & CIP100: 100μm to 6200μm

Typical Sample area: 100mm x 0.93mm

Number concentration range: 0 - 100cm3

Number of size bins: 62

Sampling Frequency: 0.1Hz - 10Hz (1D histogram), Asynchronous 2D image data

Air speed range: 0-200ms-1

Laser Wavelength: CIP100: 658nm, CIP15 642nm

Temperature: -50 to +50 DegC

Altitude: 50,000 ft

Data requirements: RS422 plus Imaging Cards in host PC.

Hot wire LWC:

LW range: 0.01 - 3gm³

Air speed range: 10 - 200 ms^-1

Sampling frequency: 0.1 to 10 Hz

Auxiliary parameters: Temperature, Pressure, Airspeed

Data:

CIP data are valid with the standard operating envelope of the aircraft and  the raw data are made available to the scientific community via the British Atmospheric Data Centre (BADC). The CIPs' are set to collect data at 1Hz, over 62 size bins. The  electronic features include user programmable sample parameters and the software enables real-time monitoring of household variables such as laser operating current, diode voltages and internal temperatures.

CIPs' performance checks includes a spinning disc alignment check which is performed between most flying periods and at the start of a cloud physics campaign. The spinning disc contains pinholes of various sizes which verifys the instrument is sizing particle shadows accurately.  A glass bead performance check is conducted pre-flight which verifys correct sizing and response of the instrument before flight. A rigorous cleaning and maintenance regime continues at FAAM laboratories which ensure the CIPs' continue to produce high quality and dependable data for use in the scientific community.

FAAM took ownership of the CIPs' in December 2010. For details of data prior to this date, please contact Phil Brown at the Met Office.

Documentation

All manuals, procedures and maintenence documents are available from FAAM (contact details below).

Further details

Contact Angela Dean at FAAM