Navis Autonomous Profiling Float

Autonomous profiling float for Argo and other programs, with Sea-Bird CTD. Sufficient power for 300 CTD profile cycles to 2000 dbars.

The Navis float has a traditional layout, with the sensor head at the top, and the buoyancy bladders at the bottom. The Navis buoyancy engine uses a positive displacement piston pump to transfer silicon oil from internal to external reservoirs to increase the float volume and cause it to rise. This system provides improved energy efficiency, better parking stability, and increased depth range over existing floats.

The Navis buoyancy engine is augmented at the sea surface by inflation of an air reservoir. This surface-following function provides excess buoyancy to improve surface communications. The open-loop air buoyancy system uses a seamless, natural-rubber, external bladder and oil-augmented bladder crush prevention.

At the surface, Navis uses a Garmin 15xL-W GPS to acquire positional information. It then transmits the acquired data via an Iridium Transceiver 9523. The Iridium antenna is mounted on the CTD end cap, and is supported by the CTD cell guard.

The Navis aluminum hull has a smaller diameter and length than existing floats, providing a lightweight and cost-effective package that requires less energy to operate. The float is powered by twelve lithium DD batteries in a Sea-Bird battery pack. The battery pack provides sufficient power for 300 CTD profile cycles to 2000 dbars.


  • Sufficient power for 300 CTD profile cycles to 2000 dbars.
  • SBE 41CP CTD; Argo standard.
    - Pump-controlled, T-C ducted flow minimizes salinity spiking.
    - Anti-foulant devices provide effective bio-fouling protection.
  • Iridium continuous circuit switched, 2-way communications for low-cost download of large amounts of data.
  • Self-ballasting, 1 day to equilibrate; ballasting and setup done at Sea-Bird prior to shipment.
  • Easy-to-use interface for mission programming, and for reprogramming while deployed.
  • Firmware based on field-proven Argo firmware.
  • Lightweight and easy to deploy (< 18.5 kg).
  • Expandable and scalable design for future missions, such as biogeochemical floats, deep floats.
  • Warranty — 100 profiles at 100% of purchase price, pro-rated thereafter.


The SBE 41CP CTD measures temperature, conductivity, and pressure continuously at 1 Hz through ascent and provides high accuracy, resolution, and stability. The pump-controlled, T-C ducted flow configuration minimizes salinity spiking caused by mismatch of temperature and conductivity measurements. The carefully engineered anti-foul protection includes anti-foulant devices, a U-shaped flow path, and an integral pump. On the float’s ascent, as it approaches 10 to 5 dbars beneath the ocean surface, the pump turns off. The U-shaped flow path prevents sea surface oils and contaminants from being ingested while proceeding through the ocean surface skin and sitting at the surface during data transmittal. Between profiles, the pump is off. The U-shaped flow path prevents water flow through the system caused by waves or currents; minute amounts of anti-foulant concentrate inside the conductivity cell to minimize bio-fouling.


See Profiling Float Product Guide for comparison of Navis and Navis BGCi floats.

Science Data (SBE 41CP CTD)

Temperature Initial accuracy ± 0.002 °C; Stability 0.0002 °C/year
Salinity Initial accuracy ± 0.002 PSS-78; Stability 0.001 PSS-78/year
Pressure Initial accuracy ± 2 decibars; Stability 0.8 decibars/year

Float Operation

Depth Rating 2000 decibars
Communications Iridium Transceiver 9523 — RUDICS, circuit switched
Position GPS, Garmin 15xL-W
Park Interval 1 - 15 days
Materials Aluminum hull, seamless natural-rubber external bladders
Ballasting Self-ballasting, 1 day to equilibrate
Weight in Air Less than 18.5 kg
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 10 years or 300 2000-dbar cycles
Memory CTD stores one 2000 decibar CTD profile; Navis stores 64 2000-dbar CTD profiles
Dimensions Hull diameter 14 cm, Ring diameter 24 cm, Total length 159 cm

How should I handle my CTD to avoid cracking the conductivity cell?

Shipping: Sea-Bird carefully packs the CTD in foam for shipping. If you are shipping the CTD or conductivity sensor, carefully pack the instrument using the original crate and packing materials, or suitable substitutes.

Use: Cracks at the C-Duct end of the conductivity cell are most often caused by:

  • Hitting the bottom, which can cause the T-C Duct to flex, resulting in cracking at the end of the cell.
  • Removing the soaker tube from the T-C duct in a rough manner, which also causes the T-C Duct to flex. Pulling the soaker tube off at an angle can be especially damaging over time to the cell. Pull the soaker tube off straight down and gently.
  • Improper disassembly of the T-C ducted temperature and conductivity sensors (SBE 25, 25plus, and 9plus) when removing them for shipment to Sea-Bird for calibration. See Shipping SBE 9plus, 25, and 25plus Temperature and Conductivity Sensors for the correct procedure.

Note: If a Tygon tube attached to the conductivity cell has dried out, yellowed, or become difficult to remove, slice (with a razor knife or blade) and peel the tube off of the conductivity cell rather than twisting or pulling the tube off.

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.