4.7 The Navigations for Spacecrafts
243
elliptical orbit; the parameter ω is used to represent the position of the elliptical
orbit; the parameter t is used to represent the starting position of the spacecraft
in the elliptical orbit. In fact, the time for the spacecraft to pass through the perigee
contains two meanings: one is the moment and another is the corresponding position,
the perigee. In practical application, the passing perigee time (t) is often replaced by
the mean anomaly (M) or true anomaly (f ). So, for a given moment, the spacecraft’s
orbit states can be determined completely by using the six orbital elements.
According to the dependence of spacecraft on the ground tracking and telemetry
stations, the spacecraft’s orbit determination can be divided into two major categories:
one is autonomous orbit determination that the spacecraft autonomously estimates the position and velocity parameters by using the data from its own measurement equipment and that there are not two-way information exchange between the
measurement equipment and the Earth or other celestial bodies, also known as
autonomous navigation, such as the celestial navigation, inertial navigation and
pulsar navigation; the other is the non-autonomous orbit determination that by
tracking and measuring the spacecraft with the radio and optical facilities at ground
TT&C stations, the spacecraft’s position and velocity parameters can be obtained
through data processing. For the spacecraft’s navigation depending on the ground
TT&C stations, if it is required to track and measure the spacecraft for an entire pass,
the need number of the deployed ground stations is
N =
14400
h
+ 2,
(4.1)
where h is the spacecraft’s orbital altitude, at a unit of km. Moreover, the ideal
distribution of the ground stations is required, which will inevitably be beyond the
territory of a country, or the ground stations have to be deployed on the sea. Obviously,
it is uneconomical and unrealistic to continuously track the LEO spacecrafts by
increasing the number of ground stations.
The spacecraft’s attitudes are to express the transformation relationship between
two coordinate systems with each other: one is the spatial reference coordinate
system, referred to as r-system; the other is the spacecraft’s body coordinate system,
referred to as b-system. When the r-system is taken as the inertial coordinate system,
the attitude of the spacecraft relative to the reference system is called inertial attitude, which is mainly used in astronomical observation satellites, and interplanetary
and interstellar flight missions. When the r-system is taken as the orbital coordinate system of the spacecraft, the attitude of the spacecraft relative to the reference
system is called attitude to the Earth, which is mainly used in navigation satellites, communication satellites, Earth remote-sensing satellites, etc. Certainly, for
spacecrafts orbiting other celestial bodies, such as the Moon’s probes and Mars’
probes, the attitudes of the spacecrafts relative to the orbital coordinate system are
the attitudes orientated to the corresponding celestial bodies. Therefore, the attitude
determination is to study the attitude measurement method of the spacecraft relative
to a certain reference system, such as the inertial reference system and the reference
243
elliptical orbit; the parameter ω is used to represent the position of the elliptical
orbit; the parameter t is used to represent the starting position of the spacecraft
in the elliptical orbit. In fact, the time for the spacecraft to pass through the perigee
contains two meanings: one is the moment and another is the corresponding position,
the perigee. In practical application, the passing perigee time (t) is often replaced by
the mean anomaly (M) or true anomaly (f ). So, for a given moment, the spacecraft’s
orbit states can be determined completely by using the six orbital elements.
According to the dependence of spacecraft on the ground tracking and telemetry
stations, the spacecraft’s orbit determination can be divided into two major categories:
one is autonomous orbit determination that the spacecraft autonomously estimates the position and velocity parameters by using the data from its own measurement equipment and that there are not two-way information exchange between the
measurement equipment and the Earth or other celestial bodies, also known as
autonomous navigation, such as the celestial navigation, inertial navigation and
pulsar navigation; the other is the non-autonomous orbit determination that by
tracking and measuring the spacecraft with the radio and optical facilities at ground
TT&C stations, the spacecraft’s position and velocity parameters can be obtained
through data processing. For the spacecraft’s navigation depending on the ground
TT&C stations, if it is required to track and measure the spacecraft for an entire pass,
the need number of the deployed ground stations is
N =
14400
h
+ 2,
(4.1)
where h is the spacecraft’s orbital altitude, at a unit of km. Moreover, the ideal
distribution of the ground stations is required, which will inevitably be beyond the
territory of a country, or the ground stations have to be deployed on the sea. Obviously,
it is uneconomical and unrealistic to continuously track the LEO spacecrafts by
increasing the number of ground stations.
The spacecraft’s attitudes are to express the transformation relationship between
two coordinate systems with each other: one is the spatial reference coordinate
system, referred to as r-system; the other is the spacecraft’s body coordinate system,
referred to as b-system. When the r-system is taken as the inertial coordinate system,
the attitude of the spacecraft relative to the reference system is called inertial attitude, which is mainly used in astronomical observation satellites, and interplanetary
and interstellar flight missions. When the r-system is taken as the orbital coordinate system of the spacecraft, the attitude of the spacecraft relative to the reference
system is called attitude to the Earth, which is mainly used in navigation satellites, communication satellites, Earth remote-sensing satellites, etc. Certainly, for
spacecrafts orbiting other celestial bodies, such as the Moon’s probes and Mars’
probes, the attitudes of the spacecrafts relative to the orbital coordinate system are
the attitudes orientated to the corresponding celestial bodies. Therefore, the attitude
determination is to study the attitude measurement method of the spacecraft relative
to a certain reference system, such as the inertial reference system and the reference