LISST-25X
Submersible laser scattering instrument that measures Particle Total Volume Particle Total Area Sauter Mean Diameter
The LISST-25X is a patented derivative product. It delivers the suspended sediment concentration and  mean size in two size classes (2.5-63 and 63-500 microns).
LISST-25 marks a generational advancement in the measurement of suspended sediments. Unlike all prior sediment sensors, optical or acoustic, the LISST-25X maintains its calibration over a 200:1 range of particle sizes.  This is the only sensor capable of holding calibration for sediment concentration regardless of particle color or size within this broad a range.
The idea behind the LISST-25X is to use shaped focal plane detectors. These detectors (see figure) derive their shape from the physics of light scattering. The shape is found such that for any size of particle in the 2.5 to 500 micron range, the instrument reports the correct volume concentration. A different shape is found to yield area concentration. The ratio of volume to area is called the Sauter Mean Diameter. The instrument employs 2 paris of shaped detectors. One pair measures particles in the 2.5 to 63 micron range, the other in the 63-500 micron range. An anti-fouling accessory BioBlock is also available for this instrument.
The instrument is self-contained, with memory and batteries. It is fully programmable to set sample rate. Data can be internally stored or captured in real time.  A depth sensor is included as standard.
Software for data offload and display is provided.
Parameters measured/derived
 - Particle Total Volume
 - Particle Total Area
 - Sauter Mean Diameter
Total Volume Measurement
 - Range: 0.1 to 1,000 micro-liters/liter
 - Accuracy: 10%
 - Resolution: 12 bits
Sampling Interval
 - Fixed Interval: 1 second to 1 day
 - Delta-Tngger-Step-Mode: Measurements made at selected fixed intervals, with storage of data occuring only if the change in total volume has exceeded the selected threshold between stored measurements
Data Storage
 - 9500 measurements of 3 parameters (Time/Date; Total Volume; Total Area)
Power Supply
 - Four D cell alkaline batteries
Physical dimensions
 - 8.0 cm dia x 45 cm L
 - 4.6kg in air

LISST-100X
Submersible laser scattering instrument that measures concentration and particle size spectra, pressure and temperature
The LISST-100X delivers the size distribution of suspended sediments in 32 logarithmically spaced size classes.  Different models of this instrument cover different rnage of sizes. 
The LISST-FLOC covers the largest sizes, 7.5 to 1500 microns (nominal), and is intended for measuring flocculated marine particles. These instruments can be used as laboratory instruments, with provided accessories. The LISST-Portable is a portable version which can be driven to a site (river, stream, highway runoff..) or carried on an airplane. 
LISST-Deep is a deep version capable of operations to 6000m.
The LISST-100X instrument is a multi-parameter system for in-situ observations of particle size distribution and volume concentration. It also records the optical transmission, pressure and temperature. The instrument is fully self-contained with battery and data-logger. It can be used with supplied programs, or in specially designed modes, e.g. event triggered based on storms (pressure variance) or fronts (temperature front). Two size-ranges are available: 1.25-250 microns (Type B) and 2.5-500 microns (Type C). Standard memory size is 16MB, suitable for storing approximately 115,000 size distributions, with option to expand to 126MB, or 1,600,000 size distributions. Special versions are available for deep-ocean, high-concentration, or low-concentration environments. At the heart of the instrument is a collimated laser diode and a specially constructed annular ring detector (see Application Note L001).
Scattering at 32 angles is the primary information that is recorded. This primary measurement is mathematically inverted to get the size distribution, and also scaled to obtain the volume scattering function (VSF), see Application Note L002. The size distribution is presented as concentration (micro-l/l) in each of 32 log-spaced size bins. Optical transmission, water depth and temperature are recorded as supporting measurements.
Parameters measured/derived
 - Size distribution
 - Volume scattering function (VSF)
 - Optical transmission
 - Pressure
 - Temperature
Optical path length
 - 5cm standard (1.5cm and 2.5cm optional)
Ports
 - One external analog input (0-5V)
 - Two external digital I/O ports (5V logic)
Optical transmission
 - 12 bit resolution
Particle size range
 - 1.25 - 250 micron standard (1.5 - 150 and 2.5 - 250 micron optional)
Resolution
 - 64 size classes, log spaced
 - VSF angle range: 1.70 mrad to 340 mrad
 - (other ranges optional)
Data storage memory
 - 512K (5000 samples)
 - expandable to 2MB (20,000 samples)
Maximum sample speed
 - 5 size distributions per second
Temperature-sensor range
 - 5- 50°c - resolution: 0.1°c
Pressure-sensor range
 - 200 meters of water
 - resolution: 5cm of water
Dimensions
 - 13cm diameter
 - 81 cm long
Weight in air
 - 12 kg
Depth rating
 - 200 meters (standard)

LISST-ST
Submersible laser scattering instrument for in-situ observations of Particle Size Spectra Settling Velocity Distribution
The LISST-ST is an extended version of the LISST-100X, with an added Settling Tube (ST stands for Settling Tube). This instrument is designed to perform submerged settling experiments to obtain settling velocities of 8 size classes.  With the settling column removed, the LISST-ST may be used as a -100X, but with less than optimal flow through the sample volume.
The LISST-ST is a submersible field instrument developed for in-situ observation of the size-dependent settling velocity distribution of suspended particles. It incorporates a mechanized Settling Column. In a Settling Experiment, a water sample is drawn and trapped. The evolution of the size distribution near the base of the settling column during the settling experiment is interpreted to estimate settling velocities. Settling velocities are estiamted for 8 log-spaced size classes covering the range 1.25-250 microns (Type B), or 2.5-500 microns (Type C). For details, please see Application Note L007. The LISST-ST is designed to carry out multiple settling experiments while submerged. A motorized mechanism operates the doors that control exchange of water between the settling column and the ambient environment.
This permits repeated settling experiments. A separate built-in motorized stirrer is used to agitate and flush out settled particles after each settling experiment.
In addition to particle size distribution histories with each settling experiment, water pressure and temperature are also recorded.
The LISST-ST is a fully autonomous, battery operated, self-contained unit. It is engineered for low power consumption and built to withstand the rigors of field deployment. Easy to program features permit flexibility in duration of experiments, and in operating modes.
Parameters measured/derived
 - Size distribution
 - Settling velocity distribution
 - Pressure
 - Temperature
Optical path length
 - 5cm standard (1.5cm and 2.5cm optional)
Particle size range
 - 1.25 - 250 micron standard (1.5 - 150 and 2.5 - 250 micron optional)
Resolution
 - 64 size classes, log spaced
Data storage memory
 - 512K (5000 samples)
 - expandable to 2MB (20,000 samples)
Maximum sample speed
 - 5 size distributions per second
Temperature-sensor range
 - 5- 50°c - resolution: 0.1°c
Pressure-sensor range
 - 200 meters of water
 - resolution: 5cm of water
Dimensions
 - 13cm diameter
 - 85 cm long
Weight in air
 - 16kg
Depth rating
 - 200 meters (standard)

LISST-SL: Easy estimates of riverine sediment fluxes
The LISST-SL is an isokinetic version of the LISST-100X developed for river sediment monitoring. It senses river velocity and adjusts intake velocity to match. Optics and electronics are enclosed. Data are stored on a bridge-top Topside box.
Sequoia Scientific, Inc. announcesthe first advanced technology laser diffraction system for measuring sedimentproperties in rivers and streams. The streamlined body is a minimum drag shape.Twin fins below the body orient the LISST-SL facing upstream before insertion.A propeller on top of the body measures river velocity. The system employsactive control of the intake pump that matches river velocity to intakevelocity making the sample acquisition isokinetic. Diffracted light is measuredin an enclosed electro-optics test section. Data are transmitted up the USGSB-reel to a ‘topside’ Control Box. The detailed size distribution and volumeconcentration is recovered after data processing. Depth, velocity, andtemperature are stored with each sample. With the included depth data, thesystem is capable of delivering sediment flux in the river.

HydroLight
A radiative transfer numerical model that computes radiance distributions and derived quantities for natural water bodies.
The HYDROLIGHT radiative transfer numerical model computes radiance distributions and related quantities (irradiances, reflectances, diffuse attenuation functions, etc.) in the ocean. Users can specify the water absorption and scattering properties, the sky conditions, and the bottom boundary conditions in various ways: by selection of built-in defaults, by reading in user-supplied data (such as WETLabs® ac-9 data), or by writing their own Fortran subroutines to define their input. HYDROLIGHT then computes the in-water light field and other quantities of interest to optical oceanographers, such as the water-leaving radiance and remote-sensing reflectance. Output is presented as ASCII printout, as Excel® spreadsheets, or as digital files designed for plotting and analysis using IDL®. HYDROLIGHT is used in various ways:
As a predictive tool
What will the oceanic light field be at some time in the future?
Given a prediction of water absorption and scattering properties, HYDROLIGHT can use that information to predict the corresponding light field. HYDROLIGHT can even become the optics component of a coupled biological-physical-optical ecosystem model.
As a data analysis tool
What was the ambient light field when the data were taken?
For example, when imaging an underwater object in the daytime, the ambient daylight may contribute noise (in this case, path radiance) to the signal of interest (the light propagating from the target to the sensor). HYDROLIGHT can compute the ambient daylight field so that it can be subtracted from the total signal received at the sensor to improve the signal-to-noise ratio of the detected signal.
As a system design tool
How would a proposed system perform under different environmental conditions?
HYDROLIGHT can serve as a controlled environment to predict what the light field received by a sensor would be under a wide range of conditions. Such control of the environment and of simulated noise cannot be obtained in the field, which is best used for final testing and evaluation of sensors that were first designed using numerical simulations.
As a teaching tool
How can someone new to the field of optical oceanography most quickly build up "intuition" or a "working knowledge" about the marine optical environment? The best way to gain such knowledge is of course to spend 20 years working as an optical oceanographer. The next best way is to use HYDROLIGHT to study how oceanic light fields depend on various environmental parameters.

	Brochure - Manual
	HYDROLIGHT Technical Documentation (1.2Mb)
	Full description of HYDROLIGHT
	What is included with a HYDROLIGHT license
	HYDROLIGHT computer requirements
	Recent publications using HYDROLIGHT
	How HYDROLIGHT models surface waves
	Angular resolution used in HYDROLIGHT
	Advice on selecting output depths for HYDROLIGHT runs