GALILEO - Understanding GPS: Principles and Applications - page 562

all GALILEO satellite signals visible 10° above the horizon (i.e., 10° mask angle). In
contrast, single-frequency user performance represents the worst case.
10.2.2 Commercial Service (CS)
The commercial service will allow the development of professional applications by
supporting the dissemination of value-added data on a dedicated commercial service
signal that can be used for supporting high-accuracy positioning applications. The
GALILEO Operating Company, in charge of deploying, financing, and operating
the system, will determine the level of performance and guarantee of service it can
offer for each commercial service on the basis of the market potential of the applica-
tions. Contractual arrangements might exist, for instance, between the GALILEO
Operating Company and third party service providers for value-added services such
as weather alerts, accident warnings, traffic information, and map updates.
10.2.3 Safety of Life (SOL) Service
The SOL service is intended for safety-critical users (e.g., those involved in maritime,
aviation, and railway modes of transportation whose applications or operations
require stringent performance and safety levels). This service will be offered
unencrypted, and the system will have the capability to authenticate the included
signals to assure that the received signals are truly those broadcast by GALILEO.
This will allow the user to periodically verify in a cryptographic way that the infor-
mation broadcast by the spacecraft is genuine. In addition to signal authentication,
the SOL service will include integrity monitoring and notification (i.e., a timely
warning will be issued to the users when the safe use of the SOL signals cannot be
guaranteed according to specifications). All of these features, together with ade-
quate service guarantees, will facilitate the development and certification of SOL
applications. E5b and L1 are the frequencies used for SOL services. As with the OS,
the SOL specifications are given for a worst-case user anywhere in the world at any
time of the day. This critical service level performance has been one of the drivers for
the design of the system. This level can support critical operations, such as aviation
precision approach, with vertical guidance where stringent levels of safety are
demanded. In addition, it will also be possible for regional service providers to mon-
itor integrity of the GALILEO signals over their region. Regional integrity data can
be broadcast directly by regional service providers using up to five authorized integ-
rity uplink channels provided by the GALILEO satellites. Alternatively, regional
integrity data can also be transmitted by regional service providers to the GALILEO
Control Centers (GCC) for indirect uplink, together with the integrity data com-
puted centrally.
10.2.4 Public Regulated Service (PRS)
The PRS will be offered only to government-authorized users requiring a higher level
of protection (e.g., increased robustness against interference or jamming). The PRS
signals will be encrypted, and access to the service will be controlled through a gov-
ernment-approved secure key distribution mechanism.