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4 Navigations from Ground to Space
system is suitable for the navigation application of three-axis stabilized spacecrafts
from the low Earth orbit to five times the altitude of geosynchronous orbit. The
measurement unit is composed of three star sensors and one Earth sensor, in which
the detector element is a focal plane array of four imaging Charge-Coupled Devices
(CCD). The strap-down star sensors will each provide a 7.1-degree Field-of-View
(FOV) and an angular measurement accuracy of better than 2 arc-seconds, and the
estimated orbit determination accuracy is 0.9 km for the Low Earth Orbit (LEO) and
9 km for the High Earth Orbit (HEO).
In 1989, an onboard navigation sensor system that is specially used to measure
the Earth, Moon and Sun was designed and developed by Microcosm Inc. in the City
of Torrance, California, USA, to autonomously determine the orbit and attitude of
spacecraft in real time. The system is called Microcosm Autonomous Navigation
System (MANS), only suitable for the spacecrafts in near-earth orbit. On the basis of
the dual cone horizon scanner, a pair of fan-shaped scanning Sun and Earth sensors
are added in the MANS. The spacecraft’s orbit and attitude parameters can be determined by measuring the angular radius of the Earth’s infrared radiation disk and the
direction vectors from the Earth’s center to the Sun and Moon. The major properties
of the MANS are: the spacecraft’s orbits and attitudes can be determined with the
measured data from a navigation sensor; the sensor system is suitable for the spacecrafts in the low and middle Earth orbits; the navigation sensor is improved from
the dual cone horizon scanner that is originally used to detect the Earth’s infrared
radiation, with the advantages of small size, lightweight, low power consumption and
low cost; the latest study achievements of orbital mechanics assisting, sensor system
error calibrating, Earth environment modeling and navigation filtering processing
are applied to the system. In March 1994, the first Space Test Experiments Platform
(STEP) spacecraft, a technology demonstration satellite whose purpose is to test the
Technology for Autonomous Operational Survivability (TAOS), was launched from
the U.S. Vandenberg AFB. The MANS was one of the TAOS experimental payloads,
and unfortunately, due to the failure of the onboard computer, the MANS measurement data in the orbit have to be transmitted to the ground for post-processing, with
the orbital determination accuracy of 200−500 m.
In fact, the above study achievements have been only in the stage of system
scheme research and critical technology verification, and have not been put into a
large number of engineering applications for spacecraft autonomous navigations.
By the 1990s, with the completion of the navigation satellite system, it has been
widely used in the autonomous navigation and precise orbit determination for the
LEO spacecrafts. From applications of highly accurate navigation, the accuracy of
traditional celestial navigation system is not comparable to that of the navigation
satellite system. Therefore, in the application of spacecraft high-precision navigation, the celestial navigation is only an auxiliary means of navigation parameter
determination. Even though, the celestial navigation usually plays a role of “ballast
stone”, in some special application fields, particularly considering the properties like
autonomy and concealment.
4 Navigations from Ground to Space
system is suitable for the navigation application of three-axis stabilized spacecrafts
from the low Earth orbit to five times the altitude of geosynchronous orbit. The
measurement unit is composed of three star sensors and one Earth sensor, in which
the detector element is a focal plane array of four imaging Charge-Coupled Devices
(CCD). The strap-down star sensors will each provide a 7.1-degree Field-of-View
(FOV) and an angular measurement accuracy of better than 2 arc-seconds, and the
estimated orbit determination accuracy is 0.9 km for the Low Earth Orbit (LEO) and
9 km for the High Earth Orbit (HEO).
In 1989, an onboard navigation sensor system that is specially used to measure
the Earth, Moon and Sun was designed and developed by Microcosm Inc. in the City
of Torrance, California, USA, to autonomously determine the orbit and attitude of
spacecraft in real time. The system is called Microcosm Autonomous Navigation
System (MANS), only suitable for the spacecrafts in near-earth orbit. On the basis of
the dual cone horizon scanner, a pair of fan-shaped scanning Sun and Earth sensors
are added in the MANS. The spacecraft’s orbit and attitude parameters can be determined by measuring the angular radius of the Earth’s infrared radiation disk and the
direction vectors from the Earth’s center to the Sun and Moon. The major properties
of the MANS are: the spacecraft’s orbits and attitudes can be determined with the
measured data from a navigation sensor; the sensor system is suitable for the spacecrafts in the low and middle Earth orbits; the navigation sensor is improved from
the dual cone horizon scanner that is originally used to detect the Earth’s infrared
radiation, with the advantages of small size, lightweight, low power consumption and
low cost; the latest study achievements of orbital mechanics assisting, sensor system
error calibrating, Earth environment modeling and navigation filtering processing
are applied to the system. In March 1994, the first Space Test Experiments Platform
(STEP) spacecraft, a technology demonstration satellite whose purpose is to test the
Technology for Autonomous Operational Survivability (TAOS), was launched from
the U.S. Vandenberg AFB. The MANS was one of the TAOS experimental payloads,
and unfortunately, due to the failure of the onboard computer, the MANS measurement data in the orbit have to be transmitted to the ground for post-processing, with
the orbital determination accuracy of 200−500 m.
In fact, the above study achievements have been only in the stage of system
scheme research and critical technology verification, and have not been put into a
large number of engineering applications for spacecraft autonomous navigations.
By the 1990s, with the completion of the navigation satellite system, it has been
widely used in the autonomous navigation and precise orbit determination for the
LEO spacecrafts. From applications of highly accurate navigation, the accuracy of
traditional celestial navigation system is not comparable to that of the navigation
satellite system. Therefore, in the application of spacecraft high-precision navigation, the celestial navigation is only an auxiliary means of navigation parameter
determination. Even though, the celestial navigation usually plays a role of “ballast
stone”, in some special application fields, particularly considering the properties like
autonomy and concealment.