Measuring soil moisture from a drone: primary school students contribute to the MEDHUSA project

Last 27 March, a team of researchers from the Institute of Space Sciences (ICE-CSIC) and members of the Institute of Space Studies of Catalonia (IEEC) visited the area around the Gaià River and its surrounding vineyard agricultural land to work alongside 5th-year primary school students from Bernardí Tolrà School (Vila-rodona).

For several hours, the pupils became “young researchers,” assisting with tasks to measure soil moisture as part of a real experimental campaign (the MEDHUSA project) aimed at validating a new measurement technique using a drone.

MEDHUSA seeks to validate the MIRROR instrument, a passive reflectometer that measures soil moisture at different depths, with the aim of contributing to precision agriculture by providing tools that enhance resilience to climate change.

This science-education activity carried out is part of the educational programme ‘CientifiKs en Joc’, promoted by the Department of Research and Universities of the Government of Catalonia. The programme, aimed at schools across Catalonia, has the primary goal of fostering an interest in science and knowledge among primary school students, while also highlighting women researchers through the design of a video game featuring an active Catalan researcher.

In addition, ‘CientifiKs en Joc’ seeks to promote creativity, interdisciplinarity and teamwork, as well as raising awareness of Catalonia’s research institutions, the work they carry out, and the people who work in them.

Climate change poses a major challenge for agriculture. Longer droughts and changes in rainfall patterns are increasing the risk of desertification. Knowing which water resources are actually available to crops therefore becomes extremely valuable information, allowing for better management of these resources with the ultimate goal of improving the resilience of the agricultural sector to climate change.

In this context, measuring vertical soil moisture profiles in agricultural areas is a key factor. This is because plants have root systems that penetrate the soil to varying depths, from just a few centimetres to a couple of metres. Some plants are therefore more drought-resistant than others if their roots reach deeper soil layers, where moisture may still be sufficient despite a lack of rainfall.

This information can be used to optimise the management of water resources and thereby improve crop health and productivity at different stages of the agricultural cycle (such as sowing, irrigation, or plant development), through actions such as selecting which crop (or variety) to plant, choosing the type of irrigation system, or applying targeted irrigation to specific agricultural plots.

The fundamental principle of a passive reflectometer involves using signals transmitted by satellites that are reflected off the ground surface to obtain its geophysical properties. The sensor designed by the ICE-CSIC/IEEC team features two innovative aspects.

Firstly, it is a dual-band reflectometer, meaning it utilises signals from two different wavelengths (in this case, 25 and 120 cm). This allows for differential penetration, enabling the estimation of soil moisture at different depths (approximately between 5 and 50 cm).

Secondly, the measurements are performed using a drone. On one hand, this allows for the validation of MIRROR’s new measurement concepts, laying the groundwork for potential future satellite missions. On the other hand, flying at low altitudes enables the validation of moisture measurements with a spatial resolution of around 30 m, thus directly characterising plots and their variability.

The validation of this technology will also allow for its transfer to the space sector, as the receiver architecture and the primary elements of the project are the same as those used by the C3SatP on-board computer. This computer was developed by the Institute of Space Studies of Catalonia within the framework of the Generalitat de Catalunya’s Catalonia Space 2030 Strategy, as well as other platforms within the space industry.