All-time surveillance is crucial to protect strategic infrastructures from possible threats, like terrorist attacks or tampering attempts of any kind, or to prevent environmental disasters, like oil spill. The appeal of the possibility of employing for this task dedicated unmanned aerial, naval, or ground vehicles (UxVs), alone or in groups, is pushing forward research in autonomous or remotely controlled vehicles. To be efficiently employed, UxVs require a complex instrumentation including highly sensitive and fine resolution sensors, employed for surveillance activities and necessary for navigation purposes. Moreover, battery autonomy is a critical issue, especially for small- or medium-size UxVs, since it limits the surveillance mission duration, as well as its operational range. Therefore, sensors employed on board of UxVs must be not only energy-efficient, but also have reduced weight and size.
Radar (RAdio Detection And Ranging) and Lidar (LIght Detection And Ranging) are widely used for remote sensing, finding a broad range of applications in the field of surveillance for military as well as for security purposes. Lidar presents the advantage of having an extremely high resolution enabling a very fine imaging of the scene under observation; on the other hand, it cannot guarantee all-time operation, since it strongly depends on optical visibility, which is not to be given for granted all the time in many surveillance scenarios. Conversely, radars exhibit all-day, all-weather operation, with optimum capabilities of target detection and tracking, but to achieve a resolution comparable to the one offered by the lidar, very complex architectures or signal processing are required. Thus, radars and lidars present complementary operational and functional features, and their joint use can be pursued to get the advantage of both, at the same time overcoming their individual shortcomings. Moreover, sensor fusion applied to their output can be helpful to analyse different phenomena or to investigate complementary properties of the same targets for multiple-feature analyses, enabling a complete and detailed situational awareness picture that supports highly efficient operations, and extending the capabilities of the existing surveillance systems.
The project CLARIFIER aims at the joint use of these two different sensors, realised as two sections of a single photonics-based system, exploiting their major advantages, and overcoming their inherent limitations. This will allow relaxing the performance requirements of each sensor, as well as their power consumption, at the same time keeping a high level of performance thanks to their cooperative operation.
Photonics nowadays acknowledged as a key enabling technology for new performance advances in microwave systems. Thanks to the coherence granted by photonics, it is possible to achieve appealing features as high signal spectral purity, frequency agility, and simultaneous multi-frequency operation. Furthermore, photonic integrated circuits (PICs) are, nowadays, mature enough to push microwave systems to a higher level the performance, also increasing reliability and mechanical robustness, at the same time decreasing size, weight, and power consumption (SWaP). Therefore, the CLARIFIER project aims at the realization of the proposed combined radar-lidar transceiver, realised as a PIC hosting a common photonic core for the microwave as well as for the optical sensor. Thanks to the mutual coherence between the two sensors, that will stem from the common generation of the radar and lidar signals, the fusion of the information or data gathered by the lidar and the radar will enrich the overall situational awareness, allowing for a better characterization of the nature and behaviour of entities in the picture.
In a nutshell, the objectives of CLARIFIER project are:
- Realise the demonstrator of a photonics-assisted, frequency-agile, hybrid radar-lidar sensor, implemented as a PIC
- Reduce to the minimum SWaP, increasing battery autonomy
- Leverage on a cooperative and adaptive joint operation of the two sensors for power consumption optimisation, increasing battery autonomy
- Give an unprecedented situational awareness exploiting sensor information fusion
- Exploiting the coherence granted by photonics, investigating the possibility of fusion of raw data gathered in the optical as well in the microwave domain, e.g. employing machine-learning techniques.
The CLARIFIER consortium, including CNIT (NPD), UPTC (PPD), and UL (Co-Director), encompasses the needed expertise for a successful implementation and test of the proposed demonstrator. The expected impact of the project outcomes on surveillance applications is attracting the interest of public and private end users, available for field trials in controlled, yet relevant environments.