A satellite equipped with optical sensors is able to capture the solar radiation reflected by the matter and to return images that show the spectral information acquired by the sensor. It is possible to obtain information about the type of material and some of its physical characteristics from the analysis of the acquired images,.

How does it work?

This type of satellite allows to investigate and monitor the territory both in the natural component – for example areas subject to natural disasters, crops and vegetation or areas exposed to hydro-geological risk – and anthropic – for example the monitoring of urban development and anthropic activities , or war zones.
The satellite equipped with a radar sensor (SAR) illuminates the ground with an electromagnetic signal (as the Sun does) and records the time it takes to return to the satellite together with the intensity with which it is reflected for each point illuminated by the signal.
The radar sensor has the potential to acquire information even in the absence of sunlight and to penetrate the cloud cover thanks to of the emission of the electromagnetic signal.

What it is used for

This type of satellites allows to identify objects on the earth’s surface and to monitor their movement over time. Radar sensors are very important tools both for monitoring slow ground movements and for post-event assessments of areas affected by natural disasters, such as floods and earthquakes due to their measurement accuracy.


Freely accessible high spatial resolution optical sensors were used, such as Landsat-8 from NASA and Sentinel-2 from the European Space Agency (Copernicus program) As part of the VESTA project.

Thematic maps were produced relating to the variation of the vegetated areas along the coastal pine forest and the expansion of the urban fabric near the archaeological site of Paestum thanks to of the optical sensor data.

How do we read optical sensor data?
The images show the urban fabric of the area in 2013 (in yellow), in 2016 (in orange) and in 2019 (in red). The comparison between the images allows to observe and monitor the evolution of urban expansion that has taken place over time.
The data from radar satellite sensors (SAR) provided information regarding the slow movements of the ground and the buildings placed above it both within the Archaeological Park of Paestum, where there are historical remains, and in the surrounding area. The experts produced speed maps relating to the slow movements of the soil to identify any significant displacements of the soil and of the structures placed on it thanks to the data acquired with these sensors.


A map of urban variation from 2013 to 2016 was drawn up comparing the images of the urban fabric seen in the Surveys Section.
The color of the polygons indicates the expansion of the urban fabric. The light-colored polygons identify areas with minimal urban expansion that increases to a deep red color for areas with greater expansion.
What emerged from the investigations carried out with radar sensors?
The image shows the results of the SAR investigations (PS technique) with the mapping of ground displacements. The yellow dots (PS, Permanent Scatterer) express in millimeters / year the movements of the “targets” identified by the electromagnetic waves sent by the sensor. There are no significant movements of the structures within the area of ​​the Archaeological Park of Paestum as it can be read from the map.