4.3 Celestial Navigation System
207
refraction. According to the optical refraction property of the Earth’s atmosphere,
the measurement equations are established with the angles of the starlight refraction
as the observables, and then the orbital parameters of spacecrafts can be solved.
The celestial navigation belongs to a passive navigation system, whose beacons
come from the celestial bodies observed directly on the movable objects, without
radiating energy to the outside. It has the advantages of autonomy, concealment,
anti-interference and complete navigation information, as well as the measurement
errors will not be accumulated over time. The observation conditions for celestial
bodies are usually ideal in the upper atmosphere or in the outer space, but they
are easily limited by the weather in the navigation application near the ground,
which requires higher luminosity of the observed objects. In addition, the output of
celestial navigation information is not continuous, the positioning time is long and
the operation process is relatively complicated. The basic observables of the celestial
navigation are angles. If there is the smaller angle error, the greater distance error
will be caused. Consequently, the positioning accuracy using the celestial navigation
reaches hundreds of meters in the ideal observation condition, and, in general, is
thousands of meters and even tens of thousands of meters.
4.3.2 Development and Application
The celestial navigation is an ancient and modern positioning technology, with a very
long history. It originates from the application of marine voyage, and then gradually
applied to aircrafts, missiles, spacecrafts and other fields. As early as 2000 years ago,
there were the written records that the astronomical ways were used for sea voyage
in China. An-Liu (179−122 B.C.) who was the king of Huainanin the Western Han
Dynasty wrote a book entitled Huai Nan Zi. In an article titled Qi Su Xun of this book,
he described: “As riding a boat, a man was confused and lost the orientation; as seeing
the Big Dipper and Pole Star, he knew right away where to go”. It shows that the Big
Dipper and Pole Star had been used to guide the ships for voyage during the Western
Han Dynasty. During the Yuan Dynasty (1271−1368), with opening up the coastal
ocean voyage routes, the celestial navigation technology was rapidly developed on
the ocean voyage, and thus the navigation method that the geographic latitude was
determined by observing the elevation angles of stars was mastered gradually. The
famous navigator in the Ming Dynasty, He Zheng (1371−1433), adopted the celestial
navigation method of “identifying the orientation with the rising and falling of the
Sun and Moon, as well as measuring the distance with the elevation angles of the Big
Dipper”, to achieve the real ocean voyage and end the history “of sailing along the
coast and with the wind during the day”. The technology of “determining the position
by leading the stars” was called “transoceanic leading-star technique”. Between
1405 and 1433, the fleets led by Zheng made seven voyages to the Western Ocean,
and sailed on the vast Indian Ocean, using the “transoceanic leading-star map” with
the constellation names indicated on the nautical chart and combining the celestial
positioning with the guiding device (celestial compass) to improve the positioning
207
refraction. According to the optical refraction property of the Earth’s atmosphere,
the measurement equations are established with the angles of the starlight refraction
as the observables, and then the orbital parameters of spacecrafts can be solved.
The celestial navigation belongs to a passive navigation system, whose beacons
come from the celestial bodies observed directly on the movable objects, without
radiating energy to the outside. It has the advantages of autonomy, concealment,
anti-interference and complete navigation information, as well as the measurement
errors will not be accumulated over time. The observation conditions for celestial
bodies are usually ideal in the upper atmosphere or in the outer space, but they
are easily limited by the weather in the navigation application near the ground,
which requires higher luminosity of the observed objects. In addition, the output of
celestial navigation information is not continuous, the positioning time is long and
the operation process is relatively complicated. The basic observables of the celestial
navigation are angles. If there is the smaller angle error, the greater distance error
will be caused. Consequently, the positioning accuracy using the celestial navigation
reaches hundreds of meters in the ideal observation condition, and, in general, is
thousands of meters and even tens of thousands of meters.
4.3.2 Development and Application
The celestial navigation is an ancient and modern positioning technology, with a very
long history. It originates from the application of marine voyage, and then gradually
applied to aircrafts, missiles, spacecrafts and other fields. As early as 2000 years ago,
there were the written records that the astronomical ways were used for sea voyage
in China. An-Liu (179−122 B.C.) who was the king of Huainanin the Western Han
Dynasty wrote a book entitled Huai Nan Zi. In an article titled Qi Su Xun of this book,
he described: “As riding a boat, a man was confused and lost the orientation; as seeing
the Big Dipper and Pole Star, he knew right away where to go”. It shows that the Big
Dipper and Pole Star had been used to guide the ships for voyage during the Western
Han Dynasty. During the Yuan Dynasty (1271−1368), with opening up the coastal
ocean voyage routes, the celestial navigation technology was rapidly developed on
the ocean voyage, and thus the navigation method that the geographic latitude was
determined by observing the elevation angles of stars was mastered gradually. The
famous navigator in the Ming Dynasty, He Zheng (1371−1433), adopted the celestial
navigation method of “identifying the orientation with the rising and falling of the
Sun and Moon, as well as measuring the distance with the elevation angles of the Big
Dipper”, to achieve the real ocean voyage and end the history “of sailing along the
coast and with the wind during the day”. The technology of “determining the position
by leading the stars” was called “transoceanic leading-star technique”. Between
1405 and 1433, the fleets led by Zheng made seven voyages to the Western Ocean,
and sailed on the vast Indian Ocean, using the “transoceanic leading-star map” with
the constellation names indicated on the nautical chart and combining the celestial
positioning with the guiding device (celestial compass) to improve the positioning