4.8 Ground Navigation Networks for Spacecrafts
263
INS. So, the NASA considers using the X-ray pulsar-based navigation technology
to enhance the autonomous navigation ability for deep-space crafts, so as to greatly
improve the navigation accuracy using the DSN in the direction perpendicular to the
line of sight. In addition, the X-ray pulsar-based navigation provides an independent
TT&C way that does not relay on the Earth-based DSN, so that the ultra-deep space
crafts can finally achieve the autonomous navigation.
4.9 Autonomous Navigation Technology for Spacecrafts
4.9.1 Concepts of Autonomous Navigation
For a spacecraft, the autonomous navigation refers to the process in which the
spacecraft without the support from the ground-based TT&C system for a long time,
relying on its onboard devices, obtains all kinds of measurement data; determines
the navigation parameters like orbit, time and attitude; guides automatically itself
operation; completes finally the scheduled missions. In general, the spacecraft’s
autonomous navigation should have five basic characteristics: navigation information integrity, real-time operation, no signals radiated, un-relying on the Earth-based
stations and long-time automatic operation. The autonomous navigation of spacecraft
has extremely important practical application value and theoretic research significance. On the one hand, it can reduce the workload of ground TT&C network, the
number of the ground TT&C stations required, the frequency of information injection from the ground stations to spacecrafts and the cost of building the spacecraft
(or constellation) systems and keeping them operation for a long time. On the other
hand, it can reduce the dependence of spacecrafts on the ground TT&C network,
and enhance the capability of the system’s anti-jam and autonomous survivability.
Therefore, the spacecraft’s autonomous navigation has been always regarded as the
power and goal for the world’s major space countries to promote the development
of astronautic technology.
Since the 1960s, based on traditional celestial navigation methods, the United
States, the Soviet Union (later Russia) and other countries have proposed many
autonomous navigation systems for spacecrafts, and developed a variety of the
onboard measurement devices, such as the horizon scanning, landmark tracker, tar
sensor, space sextant, MANS and microwave radar altimeter. However, most of the
research results have been in the stage of system simulation and flight test, and have
not been put into practical application. Although the DORIS system developed by
France and the PRARE system developed by Germany can determine the spacecraft’s orbit with high accuracy, both need to exchange information with the ground
stations, and hence do not belong to the above-defined autonomous navigation for
spacecrafts. In the past 20 years, with the development and wide application of the
GPS system, the GPS has become the main means to determine the precise orbits
of LEO satellites, but the GPS constellation itself needs the ground control network
263
INS. So, the NASA considers using the X-ray pulsar-based navigation technology
to enhance the autonomous navigation ability for deep-space crafts, so as to greatly
improve the navigation accuracy using the DSN in the direction perpendicular to the
line of sight. In addition, the X-ray pulsar-based navigation provides an independent
TT&C way that does not relay on the Earth-based DSN, so that the ultra-deep space
crafts can finally achieve the autonomous navigation.
4.9 Autonomous Navigation Technology for Spacecrafts
4.9.1 Concepts of Autonomous Navigation
For a spacecraft, the autonomous navigation refers to the process in which the
spacecraft without the support from the ground-based TT&C system for a long time,
relying on its onboard devices, obtains all kinds of measurement data; determines
the navigation parameters like orbit, time and attitude; guides automatically itself
operation; completes finally the scheduled missions. In general, the spacecraft’s
autonomous navigation should have five basic characteristics: navigation information integrity, real-time operation, no signals radiated, un-relying on the Earth-based
stations and long-time automatic operation. The autonomous navigation of spacecraft
has extremely important practical application value and theoretic research significance. On the one hand, it can reduce the workload of ground TT&C network, the
number of the ground TT&C stations required, the frequency of information injection from the ground stations to spacecrafts and the cost of building the spacecraft
(or constellation) systems and keeping them operation for a long time. On the other
hand, it can reduce the dependence of spacecrafts on the ground TT&C network,
and enhance the capability of the system’s anti-jam and autonomous survivability.
Therefore, the spacecraft’s autonomous navigation has been always regarded as the
power and goal for the world’s major space countries to promote the development
of astronautic technology.
Since the 1960s, based on traditional celestial navigation methods, the United
States, the Soviet Union (later Russia) and other countries have proposed many
autonomous navigation systems for spacecrafts, and developed a variety of the
onboard measurement devices, such as the horizon scanning, landmark tracker, tar
sensor, space sextant, MANS and microwave radar altimeter. However, most of the
research results have been in the stage of system simulation and flight test, and have
not been put into practical application. Although the DORIS system developed by
France and the PRARE system developed by Germany can determine the spacecraft’s orbit with high accuracy, both need to exchange information with the ground
stations, and hence do not belong to the above-defined autonomous navigation for
spacecrafts. In the past 20 years, with the development and wide application of the
GPS system, the GPS has become the main means to determine the precise orbits
of LEO satellites, but the GPS constellation itself needs the ground control network