The Medusa gamma Soil Moisture Sensor (gSMS) is a gamma-ray spectrometer designed to record soil moisture content stationary. The system is particularly designed for agricultural purposes. It can log the moisture content hourly and generate input for decision-making on adding water to the field. 

The system is stand-alone and can be delivered with a solar panel to account for energy consumption. The height of the detector can be adjusted to the size of the field, and most commonly, a detector height of 3 meters is used. The data recorded by the detector is automatically uploaded to a cloud service by an internal 4G connection. 

The major advantage of this sensor over standard soil moisture sensors is the large field of view. The gSMS gives an average moisture content of an entire field.  


The system comprises a 2x2 inch (100 ml) CsI-based scintillation detector connected to a tailor-made spectrum processing unit. This unit contains a 4096-channel MCA, an RTK-ready GPS, real-time data processing, embedded storage and a mobile connection to upload data to the online Medusa portal. The system works as a stand-alone unit, and the data can be viewed by connecting to the interface via WiFi or ethernet on a cabled connection. The uploaded data can be viewed from anywhere by navigating to the online portal. 

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, with count rate and activities of 40K, 238U, 232Th and 137Cs. Other radionuclides can be added on request. The data is geo-referenced using the built-in GPS.

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.


  • Measures average soil moisture of an area between 0.2 -1 hectare, depending on the installation height.

  • Measures average soil moisture of the top 30 cm.

  • It is independent of atmospheric conditions.

  • Measures one sample per hour.


Key parameters

Radiation Sensor

System Data

  • Records radioactivity and determines soil moisture content

  • Updated every hour 

  • Self-powered by solar panel (optionally)

  • Data is logged and processed in the cloud 

  • Rugged carbon housing

  • The moisture content of an entire field

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

  • 2x2 inch CsI crystal

  • Dedicated Spectrum Processing Unit comprising

    • 4096 channel MCA,

    • Spectrum stabilization

    • Nuclide-specific data

  • Housing: Carbon fibre; end caps: Anodized aluminium

  • Connectors: one 8-pin LEMO Artic grip M-series

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

  • Power input 5-35V, (3W nominally, 6W max)

  • 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