Dr Nicholas Marsden

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Instrument Support Level 4
Instrument Support Level

Instrument Support Level 4

Manufacturer & Model

Spec. Inc, USA. HVPS-3

CEDA Archive Name


Data Products


Insurance Value


Physical Dimensions

See page for details


See page for details

Daily Facility Charge



Calendar 2:
High Volume Precipitation Spectrometer (HVPS - 3)

High Volume Precipitation Spectrometer (HVPS - 3)

The High Volume Precipitation Spectrometer (HVPS) is a 2D shadow probe with a 128 element detector array focused to 150 μm per pixel in the probe sample volume (19.2 mm in total). The probe electronics are comparatively fast, giving the probe an extremely large sample volume with very little dead time. At aircraft speed, the sample volume is of the order of 37 litres per second. The HVPS detectors are a single bit (on / off).

The extremely large sample volume and large pixel size make the HVPS ideal in applications where the largest cloud particles are of interest such as cirrus measurements and precipitation formation studies.

The SPEC HVPS-3 (High Volume Precipitation Spectrometer) is a probe for measuring the size, shape, and concentration of large cloud particles. It consists of a laser beam approximately 19.2 mm in width and 161 mm in open path length. The beam is aimed at a 128 element photo-detector array. As particles pass through the sample volume, a series of one-dimensional slices of an image is built up, as elements of the photo-detector arrays are shadowed from the laser illumination. These slices are built up into two-dimensional shadow images of particles at a rate determined by the aircraft airspeed.

Due to the beam and photodetector array geometry, the probe is sensitive to particles between 150 μm and 19.2 mm – 2D detector element size up to detector array width. It’s very high sample volume means that a large number of particles are sampled, giving high spatial resolution at aircraft operating speeds and exceptional counting statistics even for the largest particles.

HVPS-3 sizing accuracy can be checked for consistency against other cloud probes such as 2DS, CIP and 3V-CPI. Periodic calibrations take place in the laboratory in Manchester, but there is no requirement for field calibration. The sizing performance of the probe is very stable.

There are no servicing requirements apart from the cleaning of the optical windows at regular intervals.

  • Normally only cotton swabs and deionised water are required. These will be supplied by the IS operating the probe.
  • Instrument Insurance
    • HVPS-3 must be insured by the user for £120K to covers loss, theft or damage to the instrument: damage being that over and above general wear and tear. The system is insured whilst it is on the research aircraft.
    • The user is responsible for the instrument from the time it leaves AMOF to the time it is returned and signed off as in an acceptable operating condition by the IS: this will be done as soon as is possible on its return.
  • Public Liability Insurance
    • The AMOF is not liable for any damage or injury arising from the deployment or operation of this instrument when unattended by the IS.
  • Shipping Expenses
    • The user is liable for all costs arising from the shipping of the instrument both to and from a deployment except on board the FAAM 146 aircraft.
  • IS T&S
    • The user is responsible for covering the travel and subsistence expenses of the IS during mobilisation and demobilisation at the FAAM base of operations at Cranfield.
    • T&S during a campaign are negotiated by FAAM.
  • For aircraft use, the instrument scientists will normally transport, install and test the probe. For other use types please consult the instrument scientist.

This is primarily an aircraft probe for use on the FAAM 146 aircraft. The design of ground-based cloud experiments is beyond the scope of this document. Please contact the IS for further information or to discuss your requirements.

Eye safety
  • The HVPS-3 is a class 3B laser device even when installed in an appropriate canister. This means it can cause immediate and irreversible sight damage. Cleaning of the optical windows should not take place with the lasers powered on.
  • Only the instrument scientist or a suitably trained person approved by the instrument scientist is permitted to approach the probe when it is powered up. Risk assessments and local rules for usage are available from the IS on request and must be adhered to at all times.
Manual handling
  • Normal precautions only.
Electrical safety
  • Under normal circumstances, no live electrical connections are exposed. High voltages exist inside the probe, so the probe must never be powered outside the canister except in the presence of the IS.
Attended operation
  • The probe is not to be powered up during aircraft refueling operations.
  • The probe is not to be powered when people are likely to be close to the beam path.
  • Restrictions on risk assessments and local rules for usage to be observed at all times.

Weight (not including shipping case): 9.5 kg

Operating temperature: 30°C to -80°C

Power consumption

  • 110 V @ 400 Hz* 5.4 A 610 W
  • 28 V DC 3.6 A 100 W
  • TOTAL 710 W

* For aircraft use it can be 50Hz.

n.b. Power consumption figure does not include the data acquisition computer.

The HVPS-3 produces binary data files containing compressed particle images, timestamps, and housekeeping variables.

While raw images can be produced fairly quickly, full quality control and production of corrected time series data are computationally expensive and time-consuming.

Field Data
  • NetCDF file containing raw total number concentration and size distribution.
  • Images as PNG files.
Archive data