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4 Navigations from Ground to Space
European civil navigation satellite program, known as Galileo navigation satellite
system [13]. In fact, the Galileo program was not officially funded by the EU and
ESA until May 2003. The constellation Walker 27/3/1 was used in the Galileo system,
with an orbital altitude of 23,616 km, an inclination of 56° to the equatorial plane
and an orbital period of 14 h and 22 min, and three in-space spare satellites were
added to the constellation. The implementation of the Galileo system was divided
into the following three phases.
The first phase was from 2003 to 2010, to test the algorithms of the Galileo satellite’s orbit determination and time synchronization. In 2004, the on-ground algorithms for the satellite’s orbit determination and time synchronization had been validated by the project on the Galileo system test bed (version 1.0), which provided
fundament knowledge to develop the space segment of the Galileo positioning
system. In December 2005, the first Galileo In-Orbit Validation Element (GIOVE)
test satellite, known as GIOVE-A, was successfully launched into the orbit with an
altitude of 23,222 km, to ensure that the Galileo system meets the frequency-filling
allocation and reservation requirements for the International Telecommunication
Union (ITU), a process that was required to be completed by June 2006. In April
2008, the second Galileo test satellite GIOVE-B was launched, with a more advanced
payload than the GIOVE-A. The Galileo navigation technique and equipment, such
as navigation signals and algorithms, onboard atomic clocks, Satellite Laser Ranging
(SLR) and space radiation environment, were tested and validated in orbits with the
GIOVE-A/B. By analyzing the data from the GIOVE-A/B, it was confirmed that
the Galileo signals could successfully be operated with the tracking performance as
expected. The experimental results based on real data from the GIOVE-A/B were
used to mitigate the risks for the In-Orbit Validation (IOV) satellites that would follow
from the ground test beds.
The second phase is from 2011 to 2013, to launch the IOV Galileo satellites.
The GIOVE-A/B satellites were followed by four IOV Galileo satellites that were
much closer to the final Galileo satellite design, and the Search and Rescue feature
was installed in the IOV satellites. In October 2011, the first two IOV satellites
were launched from Guiana Space center using a Soyuz rocket, and the other two
in October 2012. With launching the four IOV satellites, the key validation tests
were enabled since ground-based receivers like those in cars and phones need to
simultaneously track a minimum of four satellites in order to calculate their positions
in three dimensions. On March 12, 2013, a first positioning was performed using the
four IOV satellites. Once the IOV phase has been completed, the remaining satellites
would be deployed to reach the Full Operational Capability (FOC).
The third phase is from 2014 to form the Galileo constellation composed of the
FOC satellites. In August 2014, the first two FOC satellites were launched, each with
a mass of about 710 kg, but were not injected into the intended orbit due to the rocket
anomaly. In March 2015, the second two FOC satellites were launched successfully
into the orbit with an altitude of 23,616 km. As of April 2020, there were a total of 22
FOC satellites launched, and the Galileo constellation has 22 operational satellites,
including 19 FOC satellites and 3 IOV satellites.
4 Navigations from Ground to Space
European civil navigation satellite program, known as Galileo navigation satellite
system [13]. In fact, the Galileo program was not officially funded by the EU and
ESA until May 2003. The constellation Walker 27/3/1 was used in the Galileo system,
with an orbital altitude of 23,616 km, an inclination of 56° to the equatorial plane
and an orbital period of 14 h and 22 min, and three in-space spare satellites were
added to the constellation. The implementation of the Galileo system was divided
into the following three phases.
The first phase was from 2003 to 2010, to test the algorithms of the Galileo satellite’s orbit determination and time synchronization. In 2004, the on-ground algorithms for the satellite’s orbit determination and time synchronization had been validated by the project on the Galileo system test bed (version 1.0), which provided
fundament knowledge to develop the space segment of the Galileo positioning
system. In December 2005, the first Galileo In-Orbit Validation Element (GIOVE)
test satellite, known as GIOVE-A, was successfully launched into the orbit with an
altitude of 23,222 km, to ensure that the Galileo system meets the frequency-filling
allocation and reservation requirements for the International Telecommunication
Union (ITU), a process that was required to be completed by June 2006. In April
2008, the second Galileo test satellite GIOVE-B was launched, with a more advanced
payload than the GIOVE-A. The Galileo navigation technique and equipment, such
as navigation signals and algorithms, onboard atomic clocks, Satellite Laser Ranging
(SLR) and space radiation environment, were tested and validated in orbits with the
GIOVE-A/B. By analyzing the data from the GIOVE-A/B, it was confirmed that
the Galileo signals could successfully be operated with the tracking performance as
expected. The experimental results based on real data from the GIOVE-A/B were
used to mitigate the risks for the In-Orbit Validation (IOV) satellites that would follow
from the ground test beds.
The second phase is from 2011 to 2013, to launch the IOV Galileo satellites.
The GIOVE-A/B satellites were followed by four IOV Galileo satellites that were
much closer to the final Galileo satellite design, and the Search and Rescue feature
was installed in the IOV satellites. In October 2011, the first two IOV satellites
were launched from Guiana Space center using a Soyuz rocket, and the other two
in October 2012. With launching the four IOV satellites, the key validation tests
were enabled since ground-based receivers like those in cars and phones need to
simultaneously track a minimum of four satellites in order to calculate their positions
in three dimensions. On March 12, 2013, a first positioning was performed using the
four IOV satellites. Once the IOV phase has been completed, the remaining satellites
would be deployed to reach the Full Operational Capability (FOC).
The third phase is from 2014 to form the Galileo constellation composed of the
FOC satellites. In August 2014, the first two FOC satellites were launched, each with
a mass of about 710 kg, but were not injected into the intended orbit due to the rocket
anomaly. In March 2015, the second two FOC satellites were launched successfully
into the orbit with an altitude of 23,616 km. As of April 2020, there were a total of 22
FOC satellites launched, and the Galileo constellation has 22 operational satellites,
including 19 FOC satellites and 3 IOV satellites.