Navis BGCi + pH Autonomous Profiling Float with Integrated Biogeochemical Sensors

Autonomous profiling float for Argo and other programs, with Sea-Bird CTD, Dissolved Oxygen sensor, integrated WET Labs ECO-MCOMS fluorometer/backscattering sensor and Sea-Bird Scientific Float Deep SeaFET™ ph sensor. The Float Deep SeaFET adapts the field-tested MBARI/SIO/Honeywell Deep-Sea DuraFET technology to measure pH on the Navis BGCi float.

Now available with a deep, stable pH sensor, the Navis BGCi + pH introduces the Float Deep SeaFET™ to the community for autonomous profiling float missions. The Float Deep SeaFET™ is integrated into the SBE 41N profiling float CTD data stream.  This float also integrates the Float Deep SeaFET™ into the SBE 41N pumped flow path for bio-fouling protection.
The SBE 41N CTD measures conductivity, temperature, and pressure (depth). The SBE 41N manages the installed sensors to take continuous measurements at 1 Hz through ascent, and provide high accuracy, resolution, and stability data.  The pump-controlled, T-C ducted flow minimizes salinity spiking caused by mismatch of temperature and conductivity measurements.
The individually calibrated SBE 63 Optical Dissolved Oxygen sensor is integrated within the CTD flow path, providing optimal correlation with CTD measurements.
The ECO-MCOMS uses demonstrated WET Labs technology to supply three optical sensors in one, providing chlorophyll a, backscattering, and CDOM, or chlorophyll a and 2 backscattering channels. MCOMS is integrated directly into the float end cap and co-located with DO and physical measurements.
The Float Deep SeaFET™ is an adaptation of the Deep-Sea DuraFET developed collaboratively by the Monterey Bay Aquarium Research Institute (MBARI), Scripps Institution of Oceanography (SIO), and Honeywell. The Deep Sea DuraFET technology was developed by Ken Johnson at MBARI and Todd Martz at SIO.


  • Navis Autonomous Profiling Float.
  • SBE 63 Optical Dissolved Oxygen sensor.
  • WET Labs ECO-MCOMS fluorometer / backscattering sensor.
  • Float Deep SeaFET™ pH sensor.
  • SBE 41N CTD — integrated data stream for all sensors on float, and continuous profiling from 2000 dbars; same CTD family as current Argo floats.
  • Additional optional bolt-on sensors available.
  • Flexible mission sequencing, allowing more frequent sampling in upper water column.
  • Backed by Sea-Bird Scientific warranty.


  • See Profiling Float Product Guide for comparison of Navis and Navis BGCi floats.
  • For detailed information on the operation of the Navis float, see the Navis float datasheet.
  • The Float Deep SeaFET™ will be available on other profiling float platforms soon.

Initial Accuracy

pH ± 0.02 pH
Temperature ± 0.002 °C
Salinity ± 0.002 PSS-78
Pressure ± 2 decibars
Dissolved Oxygen ± 3 µmol/kg or ± 2%
Chlorophyll Fluorescence ± 0.2% of full scale (relative to specific monoculture of phytoplankton [diatom] grown in specific light/nutrient conditions)
CDOM Fluorescence ± 0.3% of full scale (relative to Quinine sulfate dihydrate)
Backscattering ± 0.2% of full scale (relative to polystyrene beads [2 µm ±0.1 µm mean diameter])

Typical Stability

pH 0.036 pH/year
Temperature 0.0002 °C/year
Salinity 0.001 PSS-78/year
Pressure 0.8 decibars/year
Dissolved Oxygen

<1 µmol/kg/100,000 samples (20 °C; sample-based drift)


Volume Change 1.7% (minimum fractional)
Depth Rating 2000 dbars
Communications Iridium Transceiver 9523 — RUDICS, circuit switched
Position GPS, Garmin 15xL-W, mean acquisition time 70 sec
Park Interval 1 - 15 days
Materials Aluminum hull, seamless natural-rubber external bladders
Weight (in Air) < 20 kg (excluding optional bolt-on sensors)
Self-Activation Starts operating automatically on deployment, when pressure reaches user-programmable setpoint
Internal Batteries 4 packs of 3 DD lithium sulfuryl chloride cells (cannot ship in passenger aircraft; Class 9 Dangerous Goods)
Power Endurance 220 2000-dbar cycles (mission dependent; excluding optional bolt-on sensors)
Memory CTD stores one 2000-dbar CTD profile
Dimensions Hull diameter 14 cm, Ring diameter 24 cm, Total length 167 cm
The list below includes (as applicable) the current product brochure, manual, and quick guide; software manual(s); and application notes.

Which Sea-Bird profiling CTD is best for my application?

Sea-Bird makes four main profiling CTD instruments, as well as several profiling CTD instruments for specialized applications.

In order of decreasing cost, the four main profiling CTD instruments are the SBE 911plus CTD, SBE 25plus Sealogger CTD, SBE 19plus SeaCAT Profiler CTD, and SBE 49 FastCAT CTD Sensor:

  • The SBE 911plus is the world’s most accurate CTD. Used by most leading oceanographic institutions, the SBE 911plus is recognized for superior performance, reliability, and ease-of-use. Features include: modular conductivity and temperature sensors, Digiquartz pressure sensor, TC-Ducted Flow and pump-controlled time response, 24 Hz sampling, 8 A/D channels and power for auxiliary sensors, modem channel for real-time water sampler control without data interruption, and optional 9600 baud serial data uplink. The SBE 911plus system consists of: SBE 9plus Underwater Unit and SBE 11plus Deck Unit. The SBE 9plus can be used in self-contained mode when integrated with the optional SBE 17plus V2 Searam. The Searam provides battery power, internal 24 Hz data logging, and an auto-fire interface to an SBE 32 Carousel Water Sampler to trigger bottle closures at pre-programmed depths.
  • The SBE 25plus Sealogger is the choice for research work from smaller vessel not equipped for real-time operation, or use by multi-discipline scientific groups requiring configuration flexibility and good accuracy and resolution on a smaller budget. The SBE 25plus is a battery-powered, internally-recording CTD featuring the same modular C & T sensors used on the SBE 9plus CTD, an integral strain gauge pressure sensor, 16 Hz sampling, 2 GB of memory, TC-Ducted Flow and pump-controlled time response, and 8 A/D channels plus 2 RS-232 channels and power for auxiliary sensors. Real-time data can be transmitted via RS-232 simultaneous with data recording. The SBE 25plus integrates easily with an SBE 32 Carousel Water Sampler or SBE 55 ECO Water Sampler for real-time or autonomous operation.
  • The SBE 19plus V2 SeaCAT Profiler is known throughout the world for good performance, reliability, and ease-of-use. An economical, battery-powered, internally-recording mini-CTD, the SBE 19plus V2 is a good choice for basic hydrography, fisheries research, environmental monitoring, and sound velocity profiling. Features include 4 Hz sampling, 6 differential A/D channels plus 1 RS-232 channel and power for auxiliary sensors, 64 MB of memory, and pump-controlled conductivity time response. Real-time data can be transmitted via RS-232 simultaneous with data recording, The SBE 19plus V2 integrates easily with an SBE 32 Carousel Water Sampler or SBE 55 ECO Water Sampler for real-time or autonomous operation.
  • The SBE 49 FastCAT is an integrated CTD sensor intended for towed vehicle, ROV, AUV, or other autonomous profiling applications. Real-time data ‑ in raw format or in engineering units ‑ is logged or telemetered by the vehicle to which it is mounted. The SBE 49’s pump-controlled, TC-ducted flow minimizes salinity spiking, and its 16 Hz sampling provides very high spatial resolution of oceanographic structures and gradients. The SBE 49 has no memory or internal batteries. The SBE 49 integrates easily with an SBE 32 Carousel Water Sampler or SBE 55 ECO Water Sampler for real-time operation.

The specialized profiling CTD instruments are the SBE 52-MP Moored Profiler, Glider Payload CTD, and SBE 41/41CP Argo CTD module:

  • The SBE 52-MP Moored Profiler is a conductivity, temperature, pressure sensor, designed for moored profiling applications in which the instrument makes vertical profile measurements from a device that travels vertically beneath a buoy, or from a buoyant sub-surface sensor package that is winched up and down from a bottom-mounted platform. The 52-MP's pump-controlled, TC-ducted flow minimizes salinity spiking. The 52-MP can optionally be configured with an SBE 43F dissolved oxygen sensor.
  • The Glider Payload CTD measures conductivity, temperature, and pressure, and optionally, dissolved oxygen (with the modular SBE 43F DO sensor). It is a modular, low-power profiling instrument for autonomous gliders with the high accuracy necessary for research, inter-comparison with moored observatory sensors, updating circulation models, and leveraging data collection opportunities from operational vehicle missions. The pressure-proof module allows glider users to exchange CTDs (and DO sensors) in the field without opening the glider pressure hull.
  • Argo floats are neutrally buoyant at depth, where they are carried by currents until periodically increasing their displacement and slowing rising to the surface. The SBE 41/41CP CTD Module obtains the latest CTD profile each time the Argo float surfaces. At the surface, the float transmits in-situ measurements and drift track data to the ARGOS satellite system. The SBE 41/41CP can be integrated with Sea-Bird's Navis float or floats from other manufacturers. The SBE 41N CTD is integrated with Sea-Bird's Navis Float with Integrated Biogeochemical Sensors and Navis BGCi + pH Float with Integrated Biogeochemical Sensors.

See Product Selection Guide for a table summarizing the features of our profiling CTDs.