4.6 Navigation Satellite System
227
body, with solar cells and radiators of thermostatic temperature regulating system
mounted on the exterior. Its orientation was by a single-axis magneto-gravitational
passive system. The hermetically sealed compartment had the equipment mounted
in cruciform bays, with the chemical batteries protecting the radio and guidance
equipment mounted at the center. The operational constellation was composed of a
minimum of six Parus satellites, each deployed in one of six orbital planes, spaced
30° apart, and one active satellite and one in-space spare was usually maintained in
each plane, with a typical lifetime of 1.5−2 years. In 1974, the first Parus satellite
Cosmos-700 was launched into the orbit, with a weight of 810 kg, an apogee of
994 km, a perigee of 960 km and an inclination of 83 degrees. The satellites transmitted the Doppler-shifted signals at around 150 and 400 MHz, which carried the
satellites’ position and orbital characteristics. In 1976, the Parus system was built,
with the positioning accuracy of better than 100 m by using the data from several
satellites, officially providing military services. Up to 2010, with the last Parus satellite Cosmos-2463 put into the orbit, there were a total of 99 Parus satellites launched.
Since then, the Parus system had completed its historical mission, gradually replaced
by Global Navigation Satellite System (GLONASS).
In addition, a complementary civilian version of the Parus military navigation
system, known as Tsikada, was designed for the Soviet Merchant Marine and
Academy of Sciences in 1974. The first civilian navigation satellite Cosmos-883
was launched in 1976 to test its performance, and the launch of Cosmos-1000 in
1978 marked the beginning of deployment of the operational system. The Tsikada
constellation consisted of a minimum of four operational satellites, each deployed
in one of four orbital planes, spaced 45° apart, whose signals were supplemented for
military users by the very similar Parus system. The Tsikada system provided global
navigation for both the Soviet (later Russian) Navy and commercial shipping. Up to
1995, as the last civilian navigation satellite Cosmos-2315 was sent into the orbit, a
total of the launched Tsikada satellites reached 20.
The first generation of navigation satellite system based on the Doppler-shifted
principle, represented by the Transit system, has the following defects:
(1) Due to small total of the satellites, it is difficult to continuously navigate and
locate. There are only five active satellites and five spare satellites in the orbits
in the Transit navigation constellation, so that the time interval between two
observations of the Transit satellites at any point on the ground is long, generally
0.8−1.6 h, and varies with time. In the low latitude area, the satellite passes 15
times a day, and in the high latitude area, the satellite passes 30 times a day,
and each passing observation time is 10−18 min. Apparently, it is difficult
for the Transit system to achieve the continuous and real-time navigating and
positioning.
(2) Due to the low Earth orbits, it is difficult to precisely determine the satellite’s
orbit parameters. The orbital altitudes of the Transit satellites are only 1100 km,
belonging to the LEO, which are greatly affected by atmospheric drag. Due
to uncertainty of the atmospheric density, satellite’s surface-to-mass ratio and
atmospheric drag coefficient, it is difficult to accurately model the atmospheric
227
body, with solar cells and radiators of thermostatic temperature regulating system
mounted on the exterior. Its orientation was by a single-axis magneto-gravitational
passive system. The hermetically sealed compartment had the equipment mounted
in cruciform bays, with the chemical batteries protecting the radio and guidance
equipment mounted at the center. The operational constellation was composed of a
minimum of six Parus satellites, each deployed in one of six orbital planes, spaced
30° apart, and one active satellite and one in-space spare was usually maintained in
each plane, with a typical lifetime of 1.5−2 years. In 1974, the first Parus satellite
Cosmos-700 was launched into the orbit, with a weight of 810 kg, an apogee of
994 km, a perigee of 960 km and an inclination of 83 degrees. The satellites transmitted the Doppler-shifted signals at around 150 and 400 MHz, which carried the
satellites’ position and orbital characteristics. In 1976, the Parus system was built,
with the positioning accuracy of better than 100 m by using the data from several
satellites, officially providing military services. Up to 2010, with the last Parus satellite Cosmos-2463 put into the orbit, there were a total of 99 Parus satellites launched.
Since then, the Parus system had completed its historical mission, gradually replaced
by Global Navigation Satellite System (GLONASS).
In addition, a complementary civilian version of the Parus military navigation
system, known as Tsikada, was designed for the Soviet Merchant Marine and
Academy of Sciences in 1974. The first civilian navigation satellite Cosmos-883
was launched in 1976 to test its performance, and the launch of Cosmos-1000 in
1978 marked the beginning of deployment of the operational system. The Tsikada
constellation consisted of a minimum of four operational satellites, each deployed
in one of four orbital planes, spaced 45° apart, whose signals were supplemented for
military users by the very similar Parus system. The Tsikada system provided global
navigation for both the Soviet (later Russian) Navy and commercial shipping. Up to
1995, as the last civilian navigation satellite Cosmos-2315 was sent into the orbit, a
total of the launched Tsikada satellites reached 20.
The first generation of navigation satellite system based on the Doppler-shifted
principle, represented by the Transit system, has the following defects:
(1) Due to small total of the satellites, it is difficult to continuously navigate and
locate. There are only five active satellites and five spare satellites in the orbits
in the Transit navigation constellation, so that the time interval between two
observations of the Transit satellites at any point on the ground is long, generally
0.8−1.6 h, and varies with time. In the low latitude area, the satellite passes 15
times a day, and in the high latitude area, the satellite passes 30 times a day,
and each passing observation time is 10−18 min. Apparently, it is difficult
for the Transit system to achieve the continuous and real-time navigating and
positioning.
(2) Due to the low Earth orbits, it is difficult to precisely determine the satellite’s
orbit parameters. The orbital altitudes of the Transit satellites are only 1100 km,
belonging to the LEO, which are greatly affected by atmospheric drag. Due
to uncertainty of the atmospheric density, satellite’s surface-to-mass ratio and
atmospheric drag coefficient, it is difficult to accurately model the atmospheric