GNSS - Global/Regional Advanced Autonomous Localization (GRAAL)

Paper number

IAC-08.B2.2.3

Author

Mr. Daniel Dassaud, CNES, France

Coauthor

Mr. Charles Fernet, Thales Alenia Space, France

Coauthor

Mr. Daniel Brocard, Centre National d'Etudes Spatiales (CNES), France

Coauthor

Mr. Lionel Ries, Centre National d'Etudes Spatiales (CNES), France

Coauthor

Mr. Jean-Luc Issler, Centre National d'Etudes Spatiales (CNES), France

Coauthor

Mr. jean-louis Damidaux, Thales Alenia Space, France

Coauthor

Mr. Christian Peyrotte, Thales Alenia Space, France

Year

2008

Abstract

The GRAAL system study phase 1 has been initiated by CNES in the frame of CNES - R and T activities. This
study has been co-financed by CNES and Thales Alenia Space.
The purpose of the first study phase of 8 months was to identify potential improvements of GALILEO system in term of navigation performance, robustness, integrity and autonomy. A second phase is still in progress.

This study propose relevant technical solutions which could be implemented in future versions of
European GNSS (improvement of GALILEO FOC or evolutions of 2nd generation GALILEO system).

The navigation performance offered by the 1st generation of the GALILEO system (IOV then FOC) depends on
ground segment ability to continuously realize monitoring and control of MEO satellites constellation (orbits,
navigation signals, etc.) in nominal conditions. In case of degraded modes of ground segment (i.e. failure or
Unavailability of ground station or ground network, etc…) this performance can be impacted.
More precisely, GRAAL system study consists mainly in conceiving a set of solutions allowing to obtain a more robust GNSS system (i.e. less vulnerable to degraded modes of ground segment). This is achieved by increasing autonomy performance and functional capabilities of space segment through addition of some components mainly on-board satellites.

This paper is organized in 5 chapters, that provide the main analysis and conclusions of GRAAL study.
The first chapter presents an overview of the GALILEO system to recall basic knowledge required as input for
this study.
The second chapter identifies the main sensitive points of GALILEO system such as the robustness and the
communication network control.                                                                                                   
The third chapter proposes a set of functions to be implemented as potential answers to improve the system. Inter
Satellite Links are proposed for communication and ranging. Signals observables are enhanced from the 1st
version of GALILEO, and introduces the capability of autonomous navigation.
The fourth chapter proposes a set of functions on board the GALILEO navigation payload in order to enhance the system observables and performances. Better optimization of satellite platform budget is a direct payback of this set of functions. Among them, payload linearization appears as an optimum solution reducing in hand the payload DC consumption with better drive of output amplifiers and one the other hand, improving the signal quality.  
The fifth chapter presents the conclusion and introduce further activities to be performed.

Abstract document

IAC-08.B2.2.3.pdf

Manuscript document

IAC-08.B2.2.3.pdf (🔒 authorized access only).

To get the manuscript, please contact IAF Secretariat.