Sequoia Scientific


Optical Volume Scattering Function and Depolarization Sensor

World’s first autonomous, submersible instrument for measuring the volume scattering function (VSF) of water with depolarization. Measures P11, P12 and P22 elements of Mueller matrix of water. Also beam attenuation c and scattering b.

The LISST-VSF covers the angular range from 0.094 to 150 degrees. Of this, the range 0.094 to 14.9 degrees is covered with Sequoia’s 32-ring detector optics as in the LISST-200X. From 15 to 150 degrees scattering from the length of a laser is viewed by a rotating eyeball. These data produce P12 and P22.

Please click here for article on how the LISST-VSF instrument operates.



  • In-situ measurements of P11, P12 and P22 elements of scattering Mueller matrix, (P11 is VSF) from 15-150º.
  • VSF (P11) only at small angles, 0.09 to 10º in 32 logarithmic steps in angles.
  • Only two detectors employed with absolute radiant sensitivity (A/W) calibration.
  • Beam attenuation measured with optics similar to our LISST-100X/200X.
  • Roving Eyeball™ optics permit 1-degree resolution in angles between 15 -150º.
  • Sampling rate at 4 seconds per measurement set (involves 2 turns of Roving Eyeball with vertical, and horizontal laser polarization).
  • Daylight rejection by laser modulation.
  • Dynamic range in VSF measurements extended via laser power dimming.
  • Data from small and large angles in a single data stream, including depth and temperature.


Parameters Measured

  • Small-angle VSF in 32 log-spaced angles, from 0.1 to ~15º.
  • VSF, P12 and P22 over 15-150º  in 1º steps.
  • Temperature from –5º to 50ºC @ 0.1ºC resolution.
  • Depth (300 m max) @ 10 cm resolution

Operating Concentration Range

  • Beam attenuation coefficient from ~0.1 to ~20 m -1


  • 515 nm fiber-coupled laser.
  • Ring Detectors for small-angle VSF.
  • Roving Eyeball and PMT for 15-150º.

Mechanical and Electrical – LISST-VSF

  • Dimensions: 13.3 cm × 86 cm (5.0″ × 45.0″) [Ø × L], plus 10 cm stand-offs
  • Weight: 13 kg (28 lbs) in air; 8 kg (17.5 lbs) in water
  • 50 m operational and 300 m maximum depth limit
  • 128 GB internal solid state drive; equivalent to 40,000 measurements
  • External power input: 12 to 16 V
  • Power drain: 700mA (measuring), 170mA quiescent.

Mechanical and Electrical – Battery

Dimensions 10 cm (4”) diameter, 52 cm (20.5”) long including handle

Weight: 6.5 kg (14.3 lbs]) in air; 2 kg (2.2 lb) in water

Voltage: 14.4 V nominal; 16 V fully charged; 12 V min. operating.

Capacity: 14 Ahr, 200 Whr

Software & Downloads

  • Datasheet (pdf)
  • Accessories

  • Laboratory Test Chamber - permits use for laboratory studies on particle VSF.
  • FAQ