A new tool for the exploitation of Galileo in space

Global Navigation Satellite Systems (GNSS), like Galileo or GPS, are today considered as “invisible utilities”. Their services, providing very precise position and timing information everywhere on Earth, are essential for many of our daily actions, and entire policy sectors depend on satellite navigation signals and services.

One of the most recent technological trends connected with the evolution of the space sector is that of the exploitation of GNSS services in space. Human space missions as well as satellites performing advanced operations use GNSS signals to navigate in space.

In this context, there is a significant international effort to ensure that navigation signals from the different GNSS systems are interoperable and accessible to a wide range of space users. The so-called “Interoperable GNSS Space Service Volume (SSV)” serves as a common framework for the use of GNSS signals and services in space. It covers a broad range of altitudes from Low-Earth Orbits (LEO) to Highly Elliptical Orbits (HEO) and beyond, thereby enhancing the capability and performance of satellite positioning, navigation and timing services.

In the near future, establishing a permanent base on the Moon will involve the use of GNSS, presenting an opportunity for Galileo to play a pivotal role. The EU’s GNSS navigation performance in space is continuously improved by integrating new services and tools.

To ensure the feasibility of all these applications, it is essential to provide the users with a comprehensive understanding of the satellite's antenna patterns, including their side lobes. Exploiting those side lobes it is essential for certain space users, leading to improved performance and enabling key applications.

In this context, the Joint Research Centre (JRC) of the European Commission in collaboration with EC DG DEFIS and ESA, has conducted technical analyses to derive the Galileo Reference Antenna Pattern (GRAP) model.

The model has been proposed to be adopted as the reference model by the Galileo Programme, in order to provide the Galileo space users with a reliable information.

From a technical perspective, the GRAP model represents the Galileo Full Operational Capability (FOC) satellites antenna pattern. In particular, the model provides the expected Equivalent Isotropic Radiated Power (EIRP) variation.

The model offers the SSV user community reliable information obtained from the characterization campaign of the Galileo FOC satellite antennas before the launch. The characterisation was performed on the isolated antennas up to higher as possible off-boresight angles.

In particular, the model is provided in terms of Equivalent Isotropic Radiated Power (EIRP) variation and is complemented with a proper estimation of the model confidence intervals. This represents for the users an essential added value, providing them with the capability to assess what likely will happen according to the current knowledge of the pattern.

The model was developed through a specific multi-step process. Indeed, it integrates available information using proper methodologies based on antenna’s characterization techniques and statistical learning.

More in-depth technical details leading to the derivation of the "Galileo Reference Antenna Pattern (GRAP)" model can be found in the following JRC Technical Report:

Reconstruction of Galileo Constellation Antenna Pattern for Space Service Volume Applications - F. Menzione, M. Sgammini, M. Paonni - 2024

See the report

Furthermore, the GRAP model is accessible to users in the form of metadata.