The Medusa Radiometrics MS-1200 MUS is the "2018" version of our good-old "MEDUSA" (Multi Element Detector for Underwater Sediment Activity) sediment mapping system. The original MEDUSA system was developed in the 90ies at the University of Groningen. The primary goal was to create a tool to map sediments and heavy minerals along the Dutch coasts. The MEDUSA system is a true "multi-sensor" system, combining a gamma-ray sensor with a sound sensor, pressure sensor, IMU and temperature sensor. The system is used as a towfish being dragged over the sediment bed while measuring the sediment's radioactivity and other sediment properties like grain size. 


The system comprises highly rugged 3x10 inch (1200 ml) CsI-based scintillation detectors connected to a tailor-made spectrum processing unit. This unit contains a 4096-channel MCA, real-time data processing and embedded storage. In addition, the system contains the auxiliary sensors:

  • Two pressure sensors allow accurate measurement of the water depth up to 60m;

  • A "sound" sensor is used to estimate the sediment roughness (grain size) and obstacles;

  • A temperature sensor monitoring water temperature;

  • An inertial motion unit (3-axis acceleration, 3-axis gyro and a magnetometer) that can be used to estimate the probe's position behind the ship.

Power and communications are transferred over a single, kevlar-strengthened coax cable of maximum 1km length.

The system works as a stand-alone unit; the data can be viewed by connecting to the interface using a cabled connection. 

The unit runs the  Medusa Detector Operation System (mDOS) that provides access to the multiple functions of the device:

  • Set-up of the system;

  • Status view to inspect data and functioning of the system;

  • Single and continuous measurement modes;

  • View the data in real-time plotted on a map;

  • Download data for custom post-processing.

The data is stored in records containing energy-stabilized gamma-ray spectra, together with count rate and activities of 40K, 238U, 232Th and 137Cs. Other radionuclides can be added on request. 

System Operation

The system is designed for minimum operator interaction. It provides various views on the data streams while being acquired, allowing for online system checks. The system has embedded data storage with a standard capacity of 16GB, yielding space for over 700 hours of continuous data logging. The system can be user-configured to output gamma-ray spectra continuously, connecting the sensor to multiple data acquisition systems.

Data acquisition occurs via the embedded web-based data acquisition system or our MASS data acquisition software. MASS is a Windows app that runs on a standard PC or laptop. In addition, the system can be integrated into any modern DAS system, like the Geoduster DAS. This way, spectrometer data can continuously be logged and combined with other sensors like GPS and elevation meters.

The system is operated from a ship. Depending on the water-depth and other conditions, the system can be connected using a simple towing cable or a full-fledged pulley-winch system. It is packed inside a protective hose to protect the system from getting damaged by objects on the water-bottom. 


Key Parameters

  • High sensitivity

  • CsI scintillator for enhanced stability

  • Ultra-rugged withstands any underwater terrain

  • Full spectrum recording

  • Automatic gain stabilization

  • Online nuclide-specific count rates

  • On-board data logging

  • Dedicated logging and monitoring software

  • Set up, control and viewing of data via a built-in web server running mDOS

Radiation Sensor

  • 3x10inch CsI crystal; other sizes and crystal types on request

  • Dedicated Spectrum Processing Unit comprising

    • 4096 channel MCA,

    • Spectrum stabilization

    • Nuclide-specific data

  • Dual depth sensor for water depth 

  • Sound sensor for sediment-bed roughness

  • IMU for positioning the sensor

  • Connected via strengthened Kevlar cable

System Data

  • Housing: 3mm Aluminum; end caps: stainless steel

  • Size: 120mm diameter x 850mm length

  • Connectors: SubCONN

  • Environmental: 
    -40 0C to +85 0C; 
    IP68 protected to 10m depth

  • Power: 220V 1A

  • Data acquisition rate: up to 1Hz

  • Data storage capacity: 16GB internal

  • Wireless connection via WIFI

  • Battery-powered

  • Connectivity: user-configurable output streams over IP or serial link

  • Data acquisition via MASS software or embedded mDOS software