Remote Sensing is a set of multidisciplinary techniques and methodologies that aim at obtaining information about the environment through “remote” measurements.
In particular, microwave remote sensing uses electromagnetic radiation with a wavelength between 1 cm and 1 m (commonly referred to as microwaves) as a measurement tool. Due to the greater wavelength compared to visible and infrared radiation, microwaves exhibit the important property of penetrating clouds, fog, and possible ash or powder coverages (for example, in case of an erupting volcano or a collapsed building). This important property makes this technique virtually suitable to work in any weather condition or environment.
Microwave remote sensing systems are classified into two groups: passive and active. Passive systems collect the radiation that is naturally emitted by the observed surface. In fact, objects emit energy at the microwave frequencies, although sometimes in an extremely small amount. These systems are generally characterized by relatively low spatial resolutions.
On the contrary, active systems are characterized by the presence of their own source (transmitter) that “lights up” the observed scene and, therefore, can be used both at night and day, independently of the presence of sun. The sensor transmits a (radio) signal in the microwave bandwidth and records the part that is backscattered by the target towards the sensor itself. The power of the backscattered signal allows to discriminate between different targets within the scene, while the time between the sent and the received signal is used to measure the distance of the target. A system that operates in this way is called RADAR (the name stands for RAdio Detection And Ranging), and may allow to obtain a “microwave image” of the observed scene.
The most commonly used microwave imaging sensor is the Synthetic Aperture Radar (SAR), that is a radar system capable of providing high-resolution microwave images. They have distinctive characteristics compared to common optical images acquired in the visible or infrared bands; for this reason, radar and optical data can be complementary, as they carry on a different informative contribution.
It is also important to highlight that the radar images can be obtained and made available to all the community, especially to those responsible for land management (Ministries and government agencies such as the Civil Protection authorities, public and local authorities, etc.), only after a significant (in terms of time and computer resources) processing operation.
The main activities of the IREA researchers working in the Microwave Remote Sensing area are focused on studying innovative methods and techniques for the processing and interpretation of these remotely sensed data. In particular, the research focuses primarily on: