…Wherein we’ll learn about the LISST-AOBS, Hyper-bb and LISST-Horizon.

(Part XII can be found here: https://www.sequoiasci.com/article/the-history-of-sequoia-part-xii/ )

After the LISST-ABS introduction in 2016, Yogi noted that the LISST-ABS and turbidity sensors have opposite-trending changing sensitivities with sediment grain size. He asked himself: why not just add them? In this accidental moment, Sequoia invented the combined technology Acousto-Optical-Backscatter sensor, LISST-AOBS (patent pending) – introduced in 2019. The AOBS marks a great advance in low-cost sediment monitoring. It uniquely holds calibration constant over a wide grain-size range, unlike the ABS and OBS. The principle is described on our website here: https://www.sequoiasci.com/article/super-turbidity-explained/ as well as in a paper we presented at the IAHR conference in Panama City, Panama in the fall of 2019: https://www.sequoiasci.com/wp-content/uploads/2019/06/Agrawal_Panama_AOBS_full_Paper.pdf

The LISST-AOBS has been selling very well to the hydropower community, in particular in South America. Here it is used for particle concentration monitoring in the water flowing through the turbines, giving the turbine operators a warning if the concentration is too high and the turbines are at risk of abrasion.

LISST-AOBS

Since 2015 Wayne Slade had been very successful in securing grants for instrumentation developments from NASA. In early 2019 this resulted in the release of two new instruments: The Hyper-bb and the LISST-Horizon. Both instruments were designed for the ocean optics community, in particular the ones concerned with biogeochemical processes and/or involved in various validation efforts related to the PACE satellite mission (https://pace.oceansciences.org/ ), scheduled to launch in 2024.

Hyper-bb optics close-up

The Hyper-bb has been a great success for Sequoia, with sales all over the world to scientists studying aquatic optics. The LISST-Horizon is a more specialized instrument, but a unit has been installed on the French research vessel R/V Tara (https://fondationtaraocean.org/en/home/ ), continuously measuring particle size and volume scattering function from water sampled via the vessel flow-through system.

LISST-Horizon front view with closed mixing chamber

In the spring of 2022, Sequoia’s scientist Thomas Leeuw was on board the Tara for six weeks. During the cruise, five different LISSTs continuously measured water properties: The LISST-200X, LISST-Holo2, LISST-Tau, Hyper-bb and LISST-Horizon. The data are currently being analyzed and will be written up in a series of small notes on Sequoia’s website, as well as peer-reviewed papers. Tom’s cruise report with impressions from the cruise can be read here: https://www.sequoiasci.com/toms-cruise/

In Part XIV we’ll learn about the LISST-Tau and some of the ongoing developments at Sequoia.