5.7 Design of Ground Test System
371
readout devices, so as to achieve the simulation confirmation of multi-channel
pulse signal control, signal processing and autonomous navigation algorithm.
(5) The remote X-ray photon detection simulating-mode is on the basis on the
pure mathematical simulation mode, by connecting with the high-precision
time synchronization device, to remotely control the modulated X-ray source,
large-size beam line channel in vacuum, and large-area array detector through
special fiber network, so as to test the functions and technical indicators of
various types of detectors, and evaluate the autonomous navigation process.
(6) The actual X-ray data processing mode is under the unified scheduling of
the network control computer, and by accessing the detected pulsar’s X-ray
data to the signal processing computer and cooperating with the computers of
pulse profile extraction, navigation database, navigation parameter estimation,
performance evaluation and navigation demonstration, to build and refine the
X-ray pulsar database, so as to carry out the post-processing confirmation of
the XPNAV, and finally achieve the construction of the unified space-ground
time reference system.
5.7.5 Numerical Experiments and Their Results
On the basis of the built ground test system of the XPNAV, the numerical experiments
can be carried out to verify the feasibility of algorithms and schemes of the XPNAV.
There are two numerical experiments and their results mainly demonstrated in this
section: one is the orbit and time parameter determination for navigation satellites;
another is the attitude parameter determination for spacecrafts.
5.7.5.1 Experiment of Orbit and Time Parameter Determination
In the long-term and high-precision autonomous navigation application for spacecrafts, the accuracy of real-time orbit determination and time synchronization is
required to be highest for the navigation satellites. In this way, the theories and
methods of autonomous navigation of the navigation satellites based on the X-ray
pulsars are completely applicable to other spacecrafts. If the X-ray pulsars can be used
to realize the long-term and high-precision autonomous navigation for the navigation
satellites, then navigation satellites are used for the ground users and LEO satellites
to navigate; for the spacecrafts in the HEO, deep space and interstellar space, the Xray pulsar can be directly used for navigation; and thus, the high-precision seamless
navigation for the space flight missions from the ground to the near-earth space, deep
space and interstellar space can be achieved [2, 30]. In this section, the numerical
experiments of the XPNAV will be demonstrated with the navigation constellation
Walker 24/6/1 as an example.
The Walker constellation, proposed by John Walker in 1970, is the uniform
configuration one, where the orbital altitudes and inclinations are the same, the orbital
371
readout devices, so as to achieve the simulation confirmation of multi-channel
pulse signal control, signal processing and autonomous navigation algorithm.
(5) The remote X-ray photon detection simulating-mode is on the basis on the
pure mathematical simulation mode, by connecting with the high-precision
time synchronization device, to remotely control the modulated X-ray source,
large-size beam line channel in vacuum, and large-area array detector through
special fiber network, so as to test the functions and technical indicators of
various types of detectors, and evaluate the autonomous navigation process.
(6) The actual X-ray data processing mode is under the unified scheduling of
the network control computer, and by accessing the detected pulsar’s X-ray
data to the signal processing computer and cooperating with the computers of
pulse profile extraction, navigation database, navigation parameter estimation,
performance evaluation and navigation demonstration, to build and refine the
X-ray pulsar database, so as to carry out the post-processing confirmation of
the XPNAV, and finally achieve the construction of the unified space-ground
time reference system.
5.7.5 Numerical Experiments and Their Results
On the basis of the built ground test system of the XPNAV, the numerical experiments
can be carried out to verify the feasibility of algorithms and schemes of the XPNAV.
There are two numerical experiments and their results mainly demonstrated in this
section: one is the orbit and time parameter determination for navigation satellites;
another is the attitude parameter determination for spacecrafts.
5.7.5.1 Experiment of Orbit and Time Parameter Determination
In the long-term and high-precision autonomous navigation application for spacecrafts, the accuracy of real-time orbit determination and time synchronization is
required to be highest for the navigation satellites. In this way, the theories and
methods of autonomous navigation of the navigation satellites based on the X-ray
pulsars are completely applicable to other spacecrafts. If the X-ray pulsars can be used
to realize the long-term and high-precision autonomous navigation for the navigation
satellites, then navigation satellites are used for the ground users and LEO satellites
to navigate; for the spacecrafts in the HEO, deep space and interstellar space, the Xray pulsar can be directly used for navigation; and thus, the high-precision seamless
navigation for the space flight missions from the ground to the near-earth space, deep
space and interstellar space can be achieved [2, 30]. In this section, the numerical
experiments of the XPNAV will be demonstrated with the navigation constellation
Walker 24/6/1 as an example.
The Walker constellation, proposed by John Walker in 1970, is the uniform
configuration one, where the orbital altitudes and inclinations are the same, the orbital