Andrew Yee[_1_]
May 16th 07, 03:53 PM
ESA News
http://www.esa.int
4 May 2007
GIOVE-A transmits first navigation message
Earlier this week, GIOVE-A successfully transmitted its first navigation
message, containing the information needed by user receivers to calculate
their position. Prior to reaching this milestone, the satellite had been
broadcasting only the data needed for measuring the receiver-to-satellite
distance.
The first Galileo navigation message was created by the navigation signal
generator unit on board GIOVE-A, using content prepared by the GIOVE Mission
Segment. This week-one navigation message was uplinked to GIOVE-A on 2 May
from the Guildford ground station operated by Surrey Satellite Technology
Ltd (United Kingdom) and then transmitted from the spacecraft to the users.
The objective of the test was to demonstrate an end-to-end link between the
Mission Segment and the user receivers. The navigation message is being
generated for demonstration purposes only -- no service guarantee is
provided.
The complete radio transmission from GIOVE-A carries a navigation signal and
a navigation message. The navigation signal contains the information needed
to accurately measure the distance from the satellite to the user receiver.
The navigation message provides the timing and spacecraft orbit data needed
to calculate the time and exact position of the satellite. One of the main
tasks of the GIOVE Mission Segment is the generation of this navigation
message.
GIOVE Mission Segment
The GIOVE Mission Segment comprises two main elements, a world-wide network
of 13 Galileo experimental sensor stations and the GIOVE Processing Centre
(GPC) located at ESA's European Space Research and Technology Centre (ESTEC)
in Noordwijk, The Netherlands. The GPC is operated by European Satellite
Navigation Industries (ESNIS) -- the new name for Galileo Industries.
In order to generate the navigation message, the sensor stations track the
signal-in-space from GIOVE-A and send the tracking information to the
processing centre. The GPC computes, among other things, the precise
satellite flight path and on-board clock model. It then generates a
prediction of the orbital path and clock performance for the near-term
future, which is the basis of the navigation message. Next, this message is
transmitted to GIOVE-A which retransmits it to the user.
Aside from navigation message generation, the primary tasks of the GIOVE
Mission Segment are performance characterisation of the on-board clocks,
orbit modelling, and operations planning & telemetry analysis for the
navigation payload.
Another validation step completed
On 12 January 2006, GIOVE A transmitted the first Galileo signals, thereby
securing the frequencies allocated to Galileo by the International
Telecommunication Union. Now, the transmissions are carrying a navigation
message -- this means that the satellite is providing information that is
needed by a receiver to calculate its position.
Although the navigation message structure of GIOVE-A is slightly different,
the GIOVE-A navigation transmissions are fully representative of those that
will be sent by the operational Galileo system. The operating principles are
identical and the achievement of the first navigation message is another
important step in the validation of the Galileo system design.
GPS interoperability
Following this successful test, in the near future GIOVE-A will begin to
continuously broadcast the navigation message, with the message content
being updated whenever the satellite is visible from the Guildford uplink
station. Additionally, the message content will be extended to include the
time offset between GPS and the experimental Galileo system. Knowing this
offset, the Experimental Galileo-GPS Time Offset (E-GGTO), will allow the
user to build a position fix using GPS satellites and GIOVE-A.
Galileo is a joint initiative between ESA and the European Commission. When
fully deployed in the early years of the next decade, it will be the first
civilian positioning system to offer global coverage.
[NOTE: Images and weblinks supporting this release are available at
http://www.esa.int/esaCP/SEM0QSU681F_index_1.html ]
http://www.esa.int
4 May 2007
GIOVE-A transmits first navigation message
Earlier this week, GIOVE-A successfully transmitted its first navigation
message, containing the information needed by user receivers to calculate
their position. Prior to reaching this milestone, the satellite had been
broadcasting only the data needed for measuring the receiver-to-satellite
distance.
The first Galileo navigation message was created by the navigation signal
generator unit on board GIOVE-A, using content prepared by the GIOVE Mission
Segment. This week-one navigation message was uplinked to GIOVE-A on 2 May
from the Guildford ground station operated by Surrey Satellite Technology
Ltd (United Kingdom) and then transmitted from the spacecraft to the users.
The objective of the test was to demonstrate an end-to-end link between the
Mission Segment and the user receivers. The navigation message is being
generated for demonstration purposes only -- no service guarantee is
provided.
The complete radio transmission from GIOVE-A carries a navigation signal and
a navigation message. The navigation signal contains the information needed
to accurately measure the distance from the satellite to the user receiver.
The navigation message provides the timing and spacecraft orbit data needed
to calculate the time and exact position of the satellite. One of the main
tasks of the GIOVE Mission Segment is the generation of this navigation
message.
GIOVE Mission Segment
The GIOVE Mission Segment comprises two main elements, a world-wide network
of 13 Galileo experimental sensor stations and the GIOVE Processing Centre
(GPC) located at ESA's European Space Research and Technology Centre (ESTEC)
in Noordwijk, The Netherlands. The GPC is operated by European Satellite
Navigation Industries (ESNIS) -- the new name for Galileo Industries.
In order to generate the navigation message, the sensor stations track the
signal-in-space from GIOVE-A and send the tracking information to the
processing centre. The GPC computes, among other things, the precise
satellite flight path and on-board clock model. It then generates a
prediction of the orbital path and clock performance for the near-term
future, which is the basis of the navigation message. Next, this message is
transmitted to GIOVE-A which retransmits it to the user.
Aside from navigation message generation, the primary tasks of the GIOVE
Mission Segment are performance characterisation of the on-board clocks,
orbit modelling, and operations planning & telemetry analysis for the
navigation payload.
Another validation step completed
On 12 January 2006, GIOVE A transmitted the first Galileo signals, thereby
securing the frequencies allocated to Galileo by the International
Telecommunication Union. Now, the transmissions are carrying a navigation
message -- this means that the satellite is providing information that is
needed by a receiver to calculate its position.
Although the navigation message structure of GIOVE-A is slightly different,
the GIOVE-A navigation transmissions are fully representative of those that
will be sent by the operational Galileo system. The operating principles are
identical and the achievement of the first navigation message is another
important step in the validation of the Galileo system design.
GPS interoperability
Following this successful test, in the near future GIOVE-A will begin to
continuously broadcast the navigation message, with the message content
being updated whenever the satellite is visible from the Guildford uplink
station. Additionally, the message content will be extended to include the
time offset between GPS and the experimental Galileo system. Knowing this
offset, the Experimental Galileo-GPS Time Offset (E-GGTO), will allow the
user to build a position fix using GPS satellites and GIOVE-A.
Galileo is a joint initiative between ESA and the European Commission. When
fully deployed in the early years of the next decade, it will be the first
civilian positioning system to offer global coverage.
[NOTE: Images and weblinks supporting this release are available at
http://www.esa.int/esaCP/SEM0QSU681F_index_1.html ]