Page 17 - ITU Journal: Volume 2, No. 1 - Special issue - Propagation modelling for advanced future radio systems - Challenges for a congested radio spectrum

ITU Journal: ICT Discoveries, Vol. 2(1), December 2019

A POWERFUL SIGNAL NEARBY L1 FREQUENCY BAND JAMMING GNSS STATIONS IN
OBSERVATOIRE DE PARIS

Pierre Uhrich, Michel Abgrall, Franziska Riedel, Baptiste Chupin, Joseph Achkar and G. Daniele Rovera
LNE-SYRTE, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, 61 avenue de l’Observatoire, 75014 Paris, France

Abstract – In the frame of the French metrology organization, the laboratory Systèmes de Référence Temps-
Espace (SYRTE) in Observatoire de Paris (OP) is in charge of fundamental activities in the time and
frequency domain. Among other systems, the laboratory is operating stations receiving signals from global
navigation satellite systems (GNSS) like the Global Positioning System (GPS) or Galileo, aiming at accurate
time transfer with other remote time laboratories. Since November 2018, the GNSS signal reception in the
L1-band has been jammed by a powerful signal transmitted near to OP in a frequency band allocated to
space to Earth satellite telecommunication. This signal power was originally more than 35 dB above the
GNSS spread-spectrum power level. A formal complaint was raised in early January 2019 to the Agence
Nationale des Fréquences (ANFR). The paper describes the jamming signal and its consequences. The effect
of this signal on L1-band reception was not the same on all OP stations, depending on the bandwidth of the
antenna around the L1 carrier, but also on the receiver’s different types. It went from no effect at all for GPS-
only stations to large data loss and noise increase for multi-GNSS stations. The power of the jamming signal
is changing with time and remains under observation. We discuss what might be done to overcome this issue.

Keywords – Galileo, GNSS, GPS, jamming, L1-band

1.7 ns [3]. In addition, LNE-SYRTE is uploading daily
1. INTRODUCTION
to the International GNSS Service (IGS) geodetic
In the frame of the French metrology organization, RINEX data from two stations: OPMT00FRA [4],
the laboratory Systèmes de Référence Temps- which is a GPS-only station, and since Summer 2018
Espace (SYRTE) in Observatoire de Paris (OP) is OP7100FRA [5], a multi-GNSS one. The laboratory is
designated by the French National Metrology also hosting a Ranging and Integrity Monitoring
Institute (NMI) Laboratoire National de Métrologie Station (RIMS), as part of the ground segment of the
et d’Essais (LNE) for fundamental activities in the European Geostationary Navigation Overlay Service
time and frequency domain. LNE-SYRTE missions (EGNOS). This RIMS-PAR allows for a direct
are, among others, the design and operation of connection to UTC(OP) of EGNOS Network Time
primary and secondary frequency standards (PSFS) (ENT), the time scale of the system [6]. Furthermore,
realizing the SI second [1], and the real-time LNE-SYRTE is contractually involved in the Time
prediction of Coordinated Universal Time (UTC) in Service Provider (TSP) of the Galileo ground
OP, UTC(OP) [2], which is the basis of French legal segment. In addition to the provision of calibrated
time. For this aim, LNE-SYRTE is operating with GPS common-view (CV) data related to UTC(OP),
other equipment stations that are able to receive the laboratory is also in charge of the relative
signals from global navigation satellite systems calibration of the GPS links between the European
(GNSS) like the Global Positioning System (GPS) or laboratories contributing to TSP and the Galileo
Galileo, aiming at achieving accurate time transfer Precise Timing Facilities (PTF). Section 2 describes
between remote clocks with other laboratories. the GNSS stations implementation and monitoring
in the OP.
A large part of the laboratory GNSS activity today is
organized to fit into the requirements of the Bureau In November 2018, the GNSS signal reception of OP
International des Poids et Mesures (BIPM), in order stations in the L1-band was suddenly jammed by a
to provide the French clock contributions for the powerful signal transmitted in a frequency band
computation of UTC. LNE-SYRTE is currently which is allocated for space to Earth satellite
continuously operating GPS time transfer stations, telecommunication, according to the International
which hardware delay calibration is provided by Telecommunication Union (ITU) regulations, as
BIPM and stays within a combined uncertainty of provided to French users by the Agence Nationale

© International Telecommunication Union, 2019 1