268
4 Navigations from Ground to Space
is broadcast to users, can be carried out; the third is the isolated mode, in which
without satellite data used, single satellite itself carries out information processing;
the fourth is the normal mode, in which all autonomous navigation operations can be
performed. The autonomous navigation function for the GPS satellites can be turned
on or off by the ground control network. When the autonomous navigation payload is
suspended, the GPS Block IIR satellites also have the functions and working modes
similar to the Block IIA satellites.
In January 1997, the development and test of the first GPS Block IIR satellite
with the autonomous navigation was completed in accordance with the requirement
of the contract, and was launched on the schedule. However, due to the failure of solid
rocket engines, the satellite took off from the launch site for 13 s and then crashed with
the rocket. In July 1997, the second Block IIR satellite was successfully launched
into orbit [22], which is the first autonomous navigation satellite deployed to the
GPS constellation. As of April 2020, there are 32 satellites in the GPS constellation,
including four satellite series of the Block IIR, IIR-M, IIF and III. All of these GPS
satellites have the autonomous navigation capability.
4.9.3 Whole Rotation of Navigation Constellation
For the autonomous navigation of navigation constellation based on the inter-satellite
crosslink, the constellation’s space orientation cannot be determined due to the lack of
external space–time reference information. As a result, the constellation regarded as
a rigid body will drift relative to the Earth-Centered Inertial (ECI) coordinate frame,
which is referred to as whole rotation of navigation constellation. In other words,
among six Keplerian elements of each navigation satellite, only the semi-major axis
(a), eccentricity (e) and mean anomaly (M) are observable, while the right ascension
(Ω) of ascending node, inclination (i) to the equatorial plane and argument (ω) of
the perigee are unobservable. Obviously, with the two-way measurement distances
between the satellites as the observables, it is impossible to eliminate or suppress the
whole rotation error of the constellation, so that it is very difficult for the navigation
constellation to operate autonomously for a long time [23].
The whole rotation error modeling is one of the key technologies to realize the
autonomous navigation of navigation constellation, and there are two problems: one
is always with the modeling error, which makes the real rotation error unable to be
separated correctly, resulting in a false rotation phenomenon of the constellation and
then the divergence of the onboard filter and the other is that it is difficult to correctly
allocate the rotation error between the ground control center and the onboard filter
[24, 25]. If the total rotation of the constellation can directly be measured by using
the star sensors to observe the changes of the background of stars, the absolute orientation of the constellation relative to the ECI frame is gotten to correct the drift errors
of the satellite’s orbits. However, it requires a very high accuracy of constellation
orientation measurement. In view of the current technical level of star sensors, it
4 Navigations from Ground to Space
is broadcast to users, can be carried out; the third is the isolated mode, in which
without satellite data used, single satellite itself carries out information processing;
the fourth is the normal mode, in which all autonomous navigation operations can be
performed. The autonomous navigation function for the GPS satellites can be turned
on or off by the ground control network. When the autonomous navigation payload is
suspended, the GPS Block IIR satellites also have the functions and working modes
similar to the Block IIA satellites.
In January 1997, the development and test of the first GPS Block IIR satellite
with the autonomous navigation was completed in accordance with the requirement
of the contract, and was launched on the schedule. However, due to the failure of solid
rocket engines, the satellite took off from the launch site for 13 s and then crashed with
the rocket. In July 1997, the second Block IIR satellite was successfully launched
into orbit [22], which is the first autonomous navigation satellite deployed to the
GPS constellation. As of April 2020, there are 32 satellites in the GPS constellation,
including four satellite series of the Block IIR, IIR-M, IIF and III. All of these GPS
satellites have the autonomous navigation capability.
4.9.3 Whole Rotation of Navigation Constellation
For the autonomous navigation of navigation constellation based on the inter-satellite
crosslink, the constellation’s space orientation cannot be determined due to the lack of
external space–time reference information. As a result, the constellation regarded as
a rigid body will drift relative to the Earth-Centered Inertial (ECI) coordinate frame,
which is referred to as whole rotation of navigation constellation. In other words,
among six Keplerian elements of each navigation satellite, only the semi-major axis
(a), eccentricity (e) and mean anomaly (M) are observable, while the right ascension
(Ω) of ascending node, inclination (i) to the equatorial plane and argument (ω) of
the perigee are unobservable. Obviously, with the two-way measurement distances
between the satellites as the observables, it is impossible to eliminate or suppress the
whole rotation error of the constellation, so that it is very difficult for the navigation
constellation to operate autonomously for a long time [23].
The whole rotation error modeling is one of the key technologies to realize the
autonomous navigation of navigation constellation, and there are two problems: one
is always with the modeling error, which makes the real rotation error unable to be
separated correctly, resulting in a false rotation phenomenon of the constellation and
then the divergence of the onboard filter and the other is that it is difficult to correctly
allocate the rotation error between the ground control center and the onboard filter
[24, 25]. If the total rotation of the constellation can directly be measured by using
the star sensors to observe the changes of the background of stars, the absolute orientation of the constellation relative to the ECI frame is gotten to correct the drift errors
of the satellite’s orbits. However, it requires a very high accuracy of constellation
orientation measurement. In view of the current technical level of star sensors, it