MATE Floats!

MATE Floats Test Video

Float Internals

MARCH 22 MATE FLOATS! Webinar Archive is here!


This challenge is part of the multi-agency GO-BGC project funded by the US National Science Foundation to build a global network of chemical and biological sensors that will monitor ocean health.

The MATE ROV Competition is pleased to announce the MATE Floats! 2021 Competition Satellite Challenge!  MATE Floats! is open to teams of students (K-12 and undergraduate) around the globe.  The task:  Build a float that is capable of descending and ascending in the water column.

To allow teams additional time to build, and so as to not overlap with the MATE ROV Competition, the MATE Floats! Challenge has been pushed to October, 2021!

The MATE Floats! Challenge will culminate in October 2021.  In an effort to both simulate the real world and mitigate the potential continued impact of COVID-19, teams will ship their floats to the University of Washington (UW) where float engineers will deploy the floats in the UW School of Oceanography's test tank and carry out the challenge.

To register for MATE Floats!, click here.  Teams must register by September 15, 2021.


The Global Ocean Biogeochemistry (GO-BGC) Array is a project funded by the US National Science Foundation (NSF) to build a global network of chemical and biological sensors that will monitor ocean health. Scientists at the Monterey Bay Aquarium Research Institute (MBARI), the University of Washington, Scripps Institution of Oceanography, Woods Hole Oceanographic Institution, and Princeton University are using this grant to build and deploy 500 robotic ocean-monitoring floats around the globe.

This new network of floats will collect data on the chemistry and the biology of the ocean from the surface to a depth of 2,000 meters. It will complement the existing Argo array of floats that currently monitors ocean temperature and salinity. Data from the GO-BGC float array will allow scientists to answer questions about ocean ecosystems, observe ocean health and productivity, and monitor the elemental cycles of carbon, oxygen, and nitrogen in the ocean through all seasons of the year. Such data are needed to improve computer models of ocean fisheries and climate, and to monitor and forecast the effects of ocean warming and ocean acidification on sea life.

Floats:  A History of Measuring and Monitoring Ocean Health

The use of subsurface, freely drifting floats to study the world ocean dates back to the 1950s, when they played a role in the discovery of oceanic eddies in the western North Atlantic and the observation of the deep western boundary current. These early floats were tracked acoustically from a nearby ship; the acoustic tracking technique was expanded and improved in the 1970s, which increased the acoustic range and mission duration. In the 1980s, a new type of non‐acoustic float was designed and deployed that was capable of profiling from 1,000 m to the surface weeks to months at a time, with missions lasting several years and float data transmitted through the ARGOS satellite system

The capabilities of these floats were further expanded with the addition of temperature profiling. Floats with the ability to profile temperature were deployed in significant numbers in the Atlantic and resulted in new insight into the formation and distribution of subtropical water and flow near the Equator. Following temperature, there was an immediate interest in measuring salinity; this was made possible through the addition of CTD (conductivity, temperature, and depth) units.

The ability of profiling floats to make reliable temperature and salinity measurements was a significant accomplishment and an essential requirement for the Argo program, which began in 1999.  Since 2007 the Argo array has been populated by over 3,000 floats, with well over one million profiles of temperature and salinity collected; that same year marked the first deployment of University of Washington (UW) Argo floats in the Southern Ocean region equipped with Iridium communications and ice‐avoidance software. The success of Argo has led to an expansion in float capabilities and a number of new research projects that use profiling floats. One of these new directions is the use of biogeochemical (BGC) sensors on floats in order to observe various aspects of the biological pump and the oceanic carbon cycle. 

GO-BGC:  The Next Generation of Float Technology

The GO-BGC Array project builds on the Southern Ocean Carbon and Climate Observations and Models (SOCCOM) project.  The SOCCOM project was funded in 2014 by the US NSF to deploy ~200 floats equipped with biogeochemical sensors over a six-year period to study carbon uptake and export in the Southern Ocean.  The GO-BGC floats are similar to those used in SOCCOM. 

GO-BGC floats will be deployed from research vessels and spend their entire lives drifting through the ocean, changing depth and collecting data at programmed intervals.  Once deployed from the ship, the float will self-activate, return to the surface and transmit data back to engineers at UW.   Following that, they will descend slowly, at a rate of about 10 cm per second, to begin their mission.  

A typical cycle for a GO-BGC float is to descend to 1,000 m depth and drift for five to 10 days, then dive to 2,000 m before returning to the surface. The float is battery-powered and able to dive and surface by changing its buoyancy, which is accomplished by pumping oil from inside the float to an external bladder and back inside again. The float hosts a suite of chemical and optical sensors, which allow it to collect data on salinity, temperature, pressure, dissolved oxygen, pH, nitrate, chlorophyll, and optical backscatter as it ascends.  When it reaches the surface, it transmits data via Iridium communications satellites. It will repeat this cycle continually for as long as the batteries allow, which is about five years.

Anatomy of a Float: The Buoyancy Engine

GO-BGC floats are similar to SOCCOM floats, whose “anatomy” is depicted in the drawing below:


Engineers at UW are responsible for the design, building, and deployment of GO-BGC floats worldwide.  Through their work with industrial partners and other academic institutions such as MBARI, engineers at UW have developed a GO-BGC float which modifies existing technology (i.e., the buoyancy engine) and adds new sensors (developed by MBARI) to collect BGC data.

The internal workings of a GO-BGC float.  Credit: Andrew Meyer, UW

The float has a fixed mass; it uses a buoyancy engine to change depth.  Similar to swim bladder in a fish, the float is capable of adjusting buoyancy to maintain a fixed depth, descending from the surface to 2000m, and ascending to the surface again.   

The float accomplishes this by moving mineral oil from inside an internal reservoir to a flexible bladder located at the bottom of and external to the float.  This displaces seawater, which slightly changes the density of the float; when this bladder inflates with oil, the float becomes less dense than the surrounding seawater and rises to the surface. When the bladder is deflated by moving mineral oil from the bladder back inside the float, the float becomes more dense than the surrounding seawater and it sinks to its profile depth.

Buoyancy engine of a GO-BGC float.  Left photo: Float with bladder empty.  Center photo: Float with bladder full.  Right photo:  Float with bladder shield.  Credit:  Andrew Meyer, UW

There are two main types of buoyancy engines used by GO-BGC floats. The first type uses a piston cylinder assembly to change buoyancy (i.e., move mineral oil); the second uses a hydraulic pump. Both use a secondary pneumatic system when at the surface to gain extra “lift” (buoyancy) in order to extend the float’s antenna above the water surface.  The antenna must be completely above the water’s surface in order to effectively communicate with and transmit data to the Iridium satellites.  However, when testing, UW engineers hard wire to and communicate directly with the float using an RS-232 serial ascii interface loop.

Pneumatic system to bring the float’s antenna above the water surface.  Credit:  Andrew Meyer, UW

Traveling the World

Through the GO-BGC Array project and the 500 floats that will be deployed over its five-year span, the US NSF made a significant investment in the world’s oceans – not to mention in a technology that is intended to survive ocean conditions and provide data, uninterrupted, for up to five years; floats can’t be retrieved for service and repair.  To that end, great care is taken in packing and shipping to prevent the float from being damaged in transit and to ensure an on-time arrival at port.  If there is damage or an operational issue, the float is not deployed, but rather is sent back to UW engineers for review and repair.  Further, if the float does not arrive on time, it literally misses the boat; the research vessel and scientific cruise does not wait.

As this text is being written, the first GO-BGC float is being readied for shipment to MBARI where it will be deployed in February of 2021.

A GO BGC float securely packed in its shipping crate.  Note that no part of the float is touching the sides of the wooden crate.  Credit:  Zach Nachod, UW

A GO BGC float ready to ship.  The float is held in place by a set of hard foam that prevents it from moving and touching the sides of the crate while in transit.  Credit:  Zach Nachod, UW

And this is where your adventure into the world of float technology and monitoring ocean health begins.


GO-BGC | Global Ocean Biogeochemistry Array

Profiling Floats in SOCCOM: Technical Capabilities for Studying the Southern Ocean

A Day in the Life of a SOCCOM Float

SOCCOM in the Tank: Testing the Floats


Teams are tasked with building a float that uses active buoyancy to descend to depth and ascend back to the surface (i.e., accomplishes one vertical profile).  Thrusters/propellers are not permitted.  Teams will be evaluated on how many profiles their floats can accomplish in 10 minutes.

  • Build a float
  • Complete as many vertical profiles as possible in 10 minutes - 1 point for each profile completed

The challenge is to complete as many vertical profiles (defined as descending to depth then ascending to the surface) as possible in 10 minutes.  Each successful vertical profile will earn the team 1 point.  A successful vertical profile is defined as any part of the float on or above the surface, descending in the water column until any part of the float touches the bottom, then ascending to and breaking the surface once again.  Once the float breaks the surface, it must hold an antenna at least 10 cm above the surface of the water for a constant 15 seconds.  If 10 cm of the antennae is not held above the water for 15 seconds, the profile is not considered successful.  A mark or ring must be incorporated onto the antenna 10 cm from the end of the antenna. 


Teams will ship their floats to UW where float engineers will deploy the floats in the UW School of Oceanography's test tank and carry out the challenge in October, 2021 (see SHIPPING below for more information).  A GO-BGC project float will be deployed in the test tank alongside the teams’ floats and will operate simultaneously.

The event will be livestreamed via Twitch so that the teams, the entire MATE competition community, and GO-BGC project partners can tune in.

NOTE:  The MATE Floats! 2021 Competition Satellite Challenge is separate from the 2023 MATE ROV Competition, but the winning team(s) will be awarded prizes.  All participating teams and their floats will also be highlighted on the MATE ROV Competition and project websites.


Operational: The float must be able to operate in a saltwater tank (density = 1021.3 kg/m3).  The depth of the tank is 4 meters (13 feet).   An updated density value will be provided to teams 4 weeks prior to the competition.

The float must be less than 1 meter in overall height.  The float may not have a diameter/length/width greater than 18 cm. 

The float must use a buoyancy engine (active buoyancy) to move down and up in the water column. 

The float must have an antenna at the top that is at least 20 cm long.  The antenna does not need to be functional.  Teams must place a mark on the antenna 10 cm from the end.  This mark must be held above the waterline for a constant 15 seconds to successfully complete a profile.  The mark must be visible to UW float engineers up to 5 meters away.

Teams are encouraged to customize their floats with logos and other designs. 

Safety: The float must not damage the pool venue.  The float must not have any protruding screws or sharp edges that might injure engineers when handling.   The float must have an attachment loop so that it can be retrieved from the bottom of the pool, if necessary.

The bottom of the float should be completely covered in rubber or other shock absorbent material so it does not damage the test tank when it strikes bottom.  Teams without a soft bottomed float will not be permitted to compete. 

Electrical: The float must use onboard batteries to power the buoyancy engine.  Tethers or connection to the surface is not permitted.

The maximum allowed voltage is 12 volts nominal. 

AAA, AA, A, A23, C, D or 9V alkaline batteries are permitted.  No other size or chemical composition is permitted.  No rechargeable batteries are permitted.  12 volt, outdoor, and/or rechargeable batteries are NOT permitted.  Lithium batteries are absolutely NOT permitted Batteries must be mounted securely within a watertight housing.

A 5-amp (or less) fuse must be installed within 5 cm of the battery positive terminal.  Teams must include power calculations in their documentation to justify the size of fuse used in their system.  Circuit breakers are not permitted.  Slow blow fuses are permitted.  Floats that blow their fuse will be removed from the test tank and their challenge ended.  Any successful profiles completed up until this time will be counted. 

Electronic and Battery Housing: their float to the challenge with their electronic and battery housing at vacuum.  Upon arrival at UW and on the day of the challenge, all electronics and battery housings MUST maintain a pressure of 0.827 bar (12 psi) absolute.  Floats that have not held a vacuum through shipping will not be allowed to compete.  Teams must include (and document) a way for UW float engineers to check the pressure within their float.  

Any electronic or battery housing must be designed so that it will release pressure if pressure inside the housing is greater than the outside pressure.  Teams may: 

  • Design their housing to freely open up if pressure builds up inside the housing. 
  • Incorporate a pressure release valve on the housing.  The pressure release valve must be rated to no more than 3 psi.

If there is no pressure release valve, under no condition should the housing be built with fasteners to hold the device together.  At least one opening must serve as a pressure release.

Teams must include (and document) a way for UW float engineers to check 1) the pressure within their electronics or battery housing and 2) the battery voltage within their battery housing.

Fluid Power:  Teams may only use water as their hydraulic fluid.  No other hydraulic fluid is permitted.  The maximum hydraulic pressure permitted is 10.33 bars (150 psig). 

Teams may only use air or inert gas as their pneumatic fluid.  No other pneumatic fluid is permitted.  The maximum pneumatic pressure permitted is 2.75 bars (40 psig). 

All pneumatic and hydraulic lines, fittings, and components must be rated for a minimum 2.5 times the maximum pressure.  Any pneumatic/hydraulic system should utilize a pressure release valve or burst disk. 

Auxiliary air systems are not permitted.  Additional pressurized gas canisters (such as Spare Air) are not permitted.  No chemical creation of gases is permitted.  All air used by the buoyancy engine must come from inside the pressure housing.


Teams are required to submit a Float Specifications and Safety document, an Operations Checklist, and a demonstration video that will be reviewed by UW float engineers prior to the challenge.  All documentation must be received by 11:59 (Hawaii time) on September 5, 2021.  Documentation should be submitted via the MATE Floats Document Submission Form.

Files should be named:  Team name_document type_2021.

For example, the operations checklist document from Team Phoenix Floats would be:  Phoenix Floats Operations Checklist 2021.  


The float specification and safety document must include:

  • Team name, school name(s), float name, and the name of all the team members.
  • A photo of the float.
  • A description and image (photo, CAD, or sketch) of the float’s buoyancy engine on the float.
  • Type of batteries used (type and number).
  • Amperage calculations and fuse selected.  Include a photo of the fuse in the fuse holder. 
  • A description of the pressure release mechanism on the float.

The Float Specifications and Safety document is limited to 2 pages, must be a PDF, and cannot exceed 2 MB.


Teams must provide an Operations Checklist, with step-by-step instructions, for turning on, setting up, and system-checking their float.  UW float engineers will use this checklist to activate the float on the day of the challenge.  The checklist MUST cover how to:

  • Check the vacuum inside the float
    • The vacuum pressure inside the float prior to shipping
  • Check the battery voltage
    • The battery voltage prior to shipping
  • Establish communications with the float
    • How to put the float to sleep
    • How to start the profiling mission

Images can be included to aid in the step-by-step instructions.

The Operations Checklist is limited to 2 pages, must be a PDF, and cannot exceed 2 MB. 

Bluetooth or WiFi must be built into the system.  If the UW float engineers cannot establish communication with float, the float will not be permitted to compete.  The means of establishing communication with the float must be included in the operations checklist.


Teams must submit a video that demonstrates:

  • Activating and checking the float
  • The float completing two profiles in a pool, tank, or other body of water that is at least 2 meters deep

The footage of the float completing two profiles must be uncut with the float in view at all times.  There is no time limit for the float to complete these two profiles.  Teams may speed up the video to cut down on viewing time, but it must be uncut. 

Videos should be uploaded to YouTube, Vimeo, or other sharable format and the link to the video submitted along with the required documents. 


Teams that submit all of the required documentation and video demonstration will be approved and permitted to ship their float to UW.   Floats must be shipped to:

Rick Rupan (MATE Floats Competition)

UW School of Oceanography

Marine Science Buildings

Room G

1501 NE Boat Street

Seattle, WA 98195

Ph:   206-453-9110

Floats must arrive at the University of Washington by October, 2021.  A deadline for arrival will be given to teams as the competition date nears.  Team’s whose floats arrive late will not participate in the challenge.  Teams outside of the U.S. should consider submitting their documentation before the deadline so that it can be reviewed and approved to allow for ample shipping time.  

Upon arrival, UW float engineers will photograph the shipping container and the unpacked float to demonstrate condition upon arrival.  UW float engineers will follow the checklist to “awaken” the float and check its vacuum pressure and voltage.  The team will be provided the time their float will be “awakened” so they can, if possible, communicate with their float.  Upon completion of the checks and communication, UW float engineers will put the float “asleep” until the challenge.


MATE Floats! Forum: Questions about float design and building specifications, as well as float challenge rules, should be posted to the Forum: 2021 MATE Floats! Challenge section of the MATE Forum Hub (

BONUS - Adopt-A-Float!!!

The GO-BGC Array project is partnering with teachers and classrooms across the country to inspire and educate students about global ocean biogeochemistry and climate change through the “Adopt-A-Float” initiative. This program creates a powerful opportunity for students to engage directly with world-class scientists and learn about their research by naming and tracking BGC (biogeochemical) floats. There is no financial cost to adopting a float! The floats profile the water column from 2000 meters to the surface every ten days for up to five year. All of the data is posted online and easily accessible.  Visit the Adopt-A-Float page for more information!