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5 X-ray Pulsar-Based Navigation: Theories and Experiments
have their own advantages and disadvantages in sensitivity, time resolution,
spatial resolution, photon arrival-time measurement accuracy, working environment temperature, reliability, volume, weight and power consumption. For
this reason, using the ground test system platform, the engineering applicability
of the X-ray detectors developed by adopting the different technical approaches
is tested and verified, to choose the types of X-ray detectors that can meet the
requirements for the space flight test and actual engineering application of the
XPNAV.
(4) Constructing the ground test system is the fundamental way to verify the system
mechanism of the XPNAV. In general, the pulsars are the most stable clocks
in nature, and with the X-ray photons radiated from the pulsars as the natural
beacons, the navigation parameters like orbit, time and attitude can be determined with high precision by measuring the pulse arrival-time and pulsar’s
image information. The spacecraft’s autonomous navigation based on the Xray pulsars can be achieved by the onboard clock phase-locked loop, orbital
parameter estimation loop and attitude parameter estimation loop. Before the
space flight test of the XPNAV is carried out, the construction of the ground
test system is the fundamental way to demonstrate the system mechanism of
the XPNAV, laying the foundation for engineering application.
(5) Constructing the ground test system is the demonstration platform for the
actual data processing of the XPNAV. The measurement data of the XPNAV are
the arrival-time sequences of X-ray photons obtained by tracking the selected
pulsars with the onboard detectors. When the measurement data are transmitted
to the ground for processing, the pulse profiles can be extracted, the pulse
arrival-time compared, the pulsar timing model and database established, the
pulsar’s period stability monitored and the system mechanism of the XPNAV
demonstrated by post-processing. Moreover, the ground test system is also
used to simulate the scene of the spacecraft’s autonomous navigation using
the X-ray pulsars, which can test the navigation algorithms, software and its
interface relations, predict and reproduce the system faults of the XPNAV, and
take the solving measures in time. Obviously, the ground test system has the
function of data processing center of the XPNAV and provides the technical
support and long-term maintenance for the space flight tests and applications
of the XPNAV.
5.7.2 The Composition and Function
The ground test system of the XPNAV is the platform to simulate the environment of
autonomous navigation for spacecrafts and test the prototype detectors. It is also the
master control center for processing the measurement data of X-rays from the pulsars,
with the test and verification capability of distribution, full-path, semi-physics and
closed-loop. By simulating the characteristics of the X-ray photon signals radiated
from the pulsars, as well as the space background noises, the key technologies,
5 X-ray Pulsar-Based Navigation: Theories and Experiments
have their own advantages and disadvantages in sensitivity, time resolution,
spatial resolution, photon arrival-time measurement accuracy, working environment temperature, reliability, volume, weight and power consumption. For
this reason, using the ground test system platform, the engineering applicability
of the X-ray detectors developed by adopting the different technical approaches
is tested and verified, to choose the types of X-ray detectors that can meet the
requirements for the space flight test and actual engineering application of the
XPNAV.
(4) Constructing the ground test system is the fundamental way to verify the system
mechanism of the XPNAV. In general, the pulsars are the most stable clocks
in nature, and with the X-ray photons radiated from the pulsars as the natural
beacons, the navigation parameters like orbit, time and attitude can be determined with high precision by measuring the pulse arrival-time and pulsar’s
image information. The spacecraft’s autonomous navigation based on the Xray pulsars can be achieved by the onboard clock phase-locked loop, orbital
parameter estimation loop and attitude parameter estimation loop. Before the
space flight test of the XPNAV is carried out, the construction of the ground
test system is the fundamental way to demonstrate the system mechanism of
the XPNAV, laying the foundation for engineering application.
(5) Constructing the ground test system is the demonstration platform for the
actual data processing of the XPNAV. The measurement data of the XPNAV are
the arrival-time sequences of X-ray photons obtained by tracking the selected
pulsars with the onboard detectors. When the measurement data are transmitted
to the ground for processing, the pulse profiles can be extracted, the pulse
arrival-time compared, the pulsar timing model and database established, the
pulsar’s period stability monitored and the system mechanism of the XPNAV
demonstrated by post-processing. Moreover, the ground test system is also
used to simulate the scene of the spacecraft’s autonomous navigation using
the X-ray pulsars, which can test the navigation algorithms, software and its
interface relations, predict and reproduce the system faults of the XPNAV, and
take the solving measures in time. Obviously, the ground test system has the
function of data processing center of the XPNAV and provides the technical
support and long-term maintenance for the space flight tests and applications
of the XPNAV.
5.7.2 The Composition and Function
The ground test system of the XPNAV is the platform to simulate the environment of
autonomous navigation for spacecrafts and test the prototype detectors. It is also the
master control center for processing the measurement data of X-rays from the pulsars,
with the test and verification capability of distribution, full-path, semi-physics and
closed-loop. By simulating the characteristics of the X-ray photon signals radiated
from the pulsars, as well as the space background noises, the key technologies,