A graphical representation of a full MEOLUT is given in Figure 5.
(FES) of a MEOLUT utilizing phase array technology. The FES consists
- Core Processor Set (CPS): for the exchange of tracking data and Monitoring and Control (M&C) data.
- Receiver Set (RS): delivering the SAR streams to the Receiver Processors (RP). Each RP digitally tracks individual satellite signals. The Master RP combines these individual processed signals and determines the position of distress.
The implemented features of the PAASAR POC is indicated in Figure 6 and Figure 7.
The following different types of customers are evident:
- MEOLUT and LEOLUT operators
- Cospas-Sarsat member states that do not yet operate a GEOLUT or MEOLUT
- Phased Array Technology (antenna) procurement entities
- Defense & Security entities
- Monitoring & Telecomunications operators
Galileo will add a substantial capability to the SAR infrastructure currently provided by Cospas-Sarsat MEOSAR (Medium Earth Orbit Search and Rescue) system. Therefore, a large number of MEOLUTs are required in the near future. An expensive element of a MEOLUT is its antenna system. Nowadays, the antenna system of a MEOLUT comprises at least 4-6 large dish antennas that need to mechanically track the individual satellites. The operation and maintenance of such an antenna system is challenging.
For the implementation of the European Ground Segment of SAR/Galileo ESA has procured 3 times 4-dish antenna MEOLUTs. These 12 antennas are needed to create sufficient coverage of Europe. However, even with these 12 antennas the currently defined MEOSAR Implementation Plan (MIP) target requirements cannot be met. It is expected that with a PAASAR system, the performance of the system is significantly improved. PAASAR provides phased array antenna technology to easily match the
current system performance.
On the operational aspect, it is a challenge to find a site where 4 or more tracking dish antennas can be installed without interfering each other. Also the scheduling of these antennas to make sure that the optimal satellites (with respect to e.g. geometry) are tracked is not an easy task. It can take up to 1 minute to reassign an antenna to another satellite. Even then, there is a risk that critical signals are lost because not all satellites can be tracked simultaneously with the available number of antennas.
Installation of a grid of dish antennas can be costly. Since the LEOSAR system will be phased out when the MEOSAR systems become operational, it would be economically beneficial if LEOLUT sites could be re-used. Since LEOLUTs use only one dish antenna, it is typically not possible to host 4 dish antennas on the same site. Additionally, since the maintenance of tracking dish antennas can be expensive, there is a need to reduce the running cost of the MEOSAR system.
To summarize, there is a need for a PAASAR MEOLUT to:
- track as many satellites simultaneously as possible,
- have a small physical footprint,
- have reliable antenna infrastructure, and
- have a low maintenance cost
The Phased Array Antenna technology has a multitude of application areas to replace conventional antenna systems and architectures given its superior performance and lower cost. The need for high performance phased arrays for large sky coverage monitoring of RF emitting entities (eg. spacecraft) is evident.
With the Phased Array Antenna (PAA) approach demonstrated in this project we are able to improve the currently available MEOLUT performance and at the same time to lower the cost.
The improvement in performance is based on the ability to track as more satellites simultaneously with a phased array compared to a traditional MEOLUT, providing a reliable and technical optimal solution. The lower cost is based on the fact that the cost of a PAASAR type MEOLUT is lower than the currently available MEOLUT solution.
Space Added Value
Phased Array Antenna approach is a technological breakthrough by allowing the system to track at least 12 satellites from a single base station, significantly increasing the performance of the system. Since the system consists of a single sphere of about 2.5 m diameter, it has a relative small footprint compared to a dish array. This would facilitate the replacements of LEOLUTs, because PAASAR enables a solution where the site infrastructure can be reused and thus decreasing cost significantly. Furthermore the maintenance cost of this solution will be lower than for a dish network since it is a solid-state solution whereas the traditional antennas are electro-mechanical.
The PAA technology by itself, and its performance, provide an additional added value in the ground station and user terminal market. The PAA technology can be applied to a multitude of space ground segment applications where complete sky coverage with a single station is required or localization of RF emitting entities.