4.6 Navigation Satellite System
225
Shortly afterward, aiming at the requirement for navigating Polaris ballistic missile
submarines, in which a launch location at sea would be accurately known, ideally
within the orders of hundred meters, McClure presented a competitive proposal on
the Polaris Doppler navigation system to the U.S. Navy’s Special Project Office,
finally accepted as the navigation satellite system, which ushered in a new era of the
development of space-based radio navigation system.
4.6.2 First-Generation Navigation Satellite System
In December 1958, under the ARPA (renamed DARPA in 1972) sponsorship, the
APL began to build the world’s first navigation satellite system for the U.S. Navy,
called the Navy Navigation Satellite System (NNSS). Since the NNSS satellite
orbits are designed to pass over the Earth’s north and south poles, the NNSS is also
known as Transit navigation system. Its basic idea was: the multiple polar orbit
satellites emitted the signals encoded with their orbit parameters at two ultra-stable
frequencies; a satellite tracking system received the signals with the two frequencies
to solve the “direct problem”; an injection station transmitted the resulting orbit
parameters to each satellite; the satellites would continue to orbit the Earth so that
the submarines with the navigation receivers could determine their positions about
once an hour anywhere on the Earth.
In September 1959, the first prototype satellite Transit-1A was launched, but was
not sent to the expected orbit due to the failure of the third stage rocket. In April 1960,
the Transit-1B satellite was successfully launched, and the test of Doppler navigation
technology was first carried out actually, which demonstrated the first engine restart
in space and the feasibility of using satellite as navigational aids. In June 1963,
the Transit 5A-3 was successfully launched into the orbit, but could not be used
for navigation due to the memory malfunction and the oscillator stability degraded.
For all that, the satellite was the first to achieve gravity-gradient stabilization, and
its other subsystems performed well. By 1964, the Transit system was officially
completed and provided navigation services for the U.S. Navy’s Polaris submarines.
In 1967, the U.S. government announced that the Transit’s navigation message would
be decrypted to offer to civilian community for use, and thus the Transit system was
quickly spread to many countries over the world and applied to many professional
fields, such as maritime navigation, hydrographic survey and geodetic survey. Up to
August 1988, as the last satellite, Transit O-31, was successfully launched into the
orbit, the total number of the launched Transit satellites got to 37. Until 1996, the
Transit system ceased service for users, replaced by the GPS.
The Transit system is a space-based, passive radio navigation system using the
Doppler shift counts, and consists of three major parts: space segment, control
segment and user segment. The space segment is a constellation composed of five
Transit satellites, besides which five in-space spare satellites are also added. These
satellites are evenly deployed on five low polar orbit planes, spaced 72 degrees apart
at right ascension of the ascending node, with the orbital altitudes of 1100 km, the
225
Shortly afterward, aiming at the requirement for navigating Polaris ballistic missile
submarines, in which a launch location at sea would be accurately known, ideally
within the orders of hundred meters, McClure presented a competitive proposal on
the Polaris Doppler navigation system to the U.S. Navy’s Special Project Office,
finally accepted as the navigation satellite system, which ushered in a new era of the
development of space-based radio navigation system.
4.6.2 First-Generation Navigation Satellite System
In December 1958, under the ARPA (renamed DARPA in 1972) sponsorship, the
APL began to build the world’s first navigation satellite system for the U.S. Navy,
called the Navy Navigation Satellite System (NNSS). Since the NNSS satellite
orbits are designed to pass over the Earth’s north and south poles, the NNSS is also
known as Transit navigation system. Its basic idea was: the multiple polar orbit
satellites emitted the signals encoded with their orbit parameters at two ultra-stable
frequencies; a satellite tracking system received the signals with the two frequencies
to solve the “direct problem”; an injection station transmitted the resulting orbit
parameters to each satellite; the satellites would continue to orbit the Earth so that
the submarines with the navigation receivers could determine their positions about
once an hour anywhere on the Earth.
In September 1959, the first prototype satellite Transit-1A was launched, but was
not sent to the expected orbit due to the failure of the third stage rocket. In April 1960,
the Transit-1B satellite was successfully launched, and the test of Doppler navigation
technology was first carried out actually, which demonstrated the first engine restart
in space and the feasibility of using satellite as navigational aids. In June 1963,
the Transit 5A-3 was successfully launched into the orbit, but could not be used
for navigation due to the memory malfunction and the oscillator stability degraded.
For all that, the satellite was the first to achieve gravity-gradient stabilization, and
its other subsystems performed well. By 1964, the Transit system was officially
completed and provided navigation services for the U.S. Navy’s Polaris submarines.
In 1967, the U.S. government announced that the Transit’s navigation message would
be decrypted to offer to civilian community for use, and thus the Transit system was
quickly spread to many countries over the world and applied to many professional
fields, such as maritime navigation, hydrographic survey and geodetic survey. Up to
August 1988, as the last satellite, Transit O-31, was successfully launched into the
orbit, the total number of the launched Transit satellites got to 37. Until 1996, the
Transit system ceased service for users, replaced by the GPS.
The Transit system is a space-based, passive radio navigation system using the
Doppler shift counts, and consists of three major parts: space segment, control
segment and user segment. The space segment is a constellation composed of five
Transit satellites, besides which five in-space spare satellites are also added. These
satellites are evenly deployed on five low polar orbit planes, spaced 72 degrees apart
at right ascension of the ascending node, with the orbital altitudes of 1100 km, the