GISAR
Galileo Implementation of Search And Rescue interfaces

Members of the consortium have been involved in all previous SAR/Galileo studies back to Galileo Phase B2 and have led the definition of SAR/Galileo at system, segment and element levels. The consortium is therefore well aware of the benefits provided by the current COSPAS-SARSAT system, as well as its weaknesses and the requirements of its operators. The planned inclusion of a SAR payload in the Galileo satellites represents a major opportunity to dramatically enhance the performance provided by this system, and to ultimately save more lives.

The MEOLUT prototype will offer a proof-of-concept platform to present the new SAR/Galileo system to COSPAS-SARSAT. It will also represent a test bench for technical and operational purposes as a major step towards the final MEOLUT. Regarding the demanding performance requested of the algorithms, i.e. to combine different satellite constellations’ relayed signals to decode a beacon message and find the position of that beacon on earth with high accuracy in a short time, will be achieved by means of specifically designed and optimised algorithms.

These algorithms are verified with the aid of extensive simulations with specially developed tools which recreate the different elements that constitute the system and with real data, thanks to the experimentation with real SAR signals from existing satellites (e.g. DASS proof-of-concept).

The main objective of the GISAR project is the design, development and validation of a MEOSAR (medium Earth orbit search and rescue) ground segment prototype, as well as the participation in both the DASS POC experimentation and the Galileo In-Orbit Validation (IOV) phase.

Description

The main source of research activities derives from the new MEOLUT concept. The subject of these activities includes SAR processing algorithms, MEOLUT antenna and RF front-end and experimentation with DASS and SAR Galileo signals. The signal processing algorithms implemented at the MEOLUT are responsible for producing accurate results, ultimately for the final performance levels; thus MEOSAR represents a benefit with respect to the current LEO/GEOSAR systems. Location techniques using the wealth of information provided by the simultaneously received signals are providing far-reaching benefits in terms of location accuracy and responsiveness, crucial for rescue operations.

Furthermore, the consecutive reception of bursts for the same distress event provides a degree of diversity that will help to reduce the influence of noise and enhance BER, location accuracy, etc. The signal processing techniques implemented in the MEOLUT prototype are the result of a trade-off between the power and flexibility of state-of-the-art techniques versus the complexity and cost brought about by these techniques. Two solutions have been traded-off for the MEOLUT front end: one is based on the use of a set of steerable dish antennas, and another is based on the use of an array antenna with digital beamforming and spatial processing techniques. The MEOLUT development intends to perform a preliminary experimentation with DASS and IOV SAR/Galileo signals. The core of these experiments is the reception of signals in S-band and L-band to provide a preliminary assessment of the MEOSAR concept, including initial performance comparison between MEOSAR and LEO/GEOSAR systems.

Objectives

The main objective of the GISAR project is the design, development and validation of a MEOSAR ground segment prototype, as well as participating in the Galileo In-Orbit Validation (IOV) phase. The MEOSAR ground segment prototype consists of a medium Earth orbit local user terminal (MEOLUT) prototype and a return link service provider (RLSP) prototype. The MEOLUT prototype is a receiver station capable of processing the SAR/Galileo distress signals transmitted by COSPAS-SARSAT emergency beacons, recovering the transmitted beacon message and locating the user in distress. The RLSP prototype manages the dissemination of return link messages providing feedback information to the beacon.

This project is developing a prototype of a MEOSAR ground station which will provide significant improvements over the ones currently in use in the COSPAS-SARSAT system, including higher accuracy and responsiveness. The targeted operational MEOLUT will also be affordable equipment that can be used worldwide, thereby enhancing the rescue activities for remote regions by allowing the deployment of a wider network. The implementation, test and validation plan for the developed prototype are also considered, together with an implementation and operational plan for the permanent or definitive MEOSAR equipment. Finally a set of enablers for the MEOLUT development are performed which will aim at ensuring the success of SAR/Galileo activities.