4.6 Navigation Satellite System
229
Chinese BeiDou navigation satellite system and European Galileo navigation satellite system, are four core providers designated by the International Committee on
Global navigation satellite system (ICG), and will be highlighted for their introductions in this section. In addition, the Japanese Quasi Zenith Satellite System (QZSS)
and the Indian Region Navigation Satellite System (IRNSS) are also developed by
using the single-way timing and ranging ways. Both the QZSS and IRNSS, which
are the regional navigation systems, can usually be found from the related references
for the interested readers, and are not going to be further described in this book.
4.6.3.1 GPS System
In 1960s, besides the Transit system, there were also three navigation satellite test
programs developed by the U.S. Forces. One was the Project 621B initiated by
the Space Division of the U.S. Air Force in 1963; the other was the TIMATION
program, which was conceived and developed by the Naval Center for Space Technology (NCST) at Naval Research Laboratory (NRL) in Washington D. C. beginning
in 1964; the third was the Sequential Collation of Range (SECOR) system developed by the U.S. Army, and the first SECOR satellite was launched for military
geodetic surveying in 1964.
The Project 621B’s proposal was presented originally by Ivan A. Getting
(1912−2003) who was then-president of the Aerospace Corporation. Seeing the
need for a new satellite-based navigation system, Ivan Getting envisioned a more
accurate positioning system that would be available in three dimensions, 24 h a
day, 7 days a week. At that time, Getting’s energy and foresight were essential to
gaining the Air Force support to study the system alternatives. In the Project 621B,
the passive-ranging technique was used to eliminate the need for an extremely stable
clock in the user equipment and provide three-dimensional positioning. Moreover,
the Code Division Multiple Access (CDMA) signal structure was also designed for
the satellites, and the prototype versions of CDMA navigation receivers were developed. Between 1968 and 1972, using the receiver on board of aircrafts to receive
from the ground-based pseudo-satellite signals, the Project’s tests were carried out
at White Sands Missile Range, New Mexico, to verify the feasibility of choosing
CDMA as the passive-ranging signal and other related techniques.
The core concept of TIMATION was a time-based navigation system with passive
ranging, circular orbits and space-borne high-precision clocks synchronized to a
master clock, presented by Roger L. Easton (1921−2014), a scientist and engineer at
the NRL. In May 1967, the first test satellite TIMATION-1 was launched successfully,
which was a small satellite with a weight of 38.3 kg and a power of 6 W, and its key
feature was to carry a very stable quartz clock. In September 1969, the TIMATION-2
satellite was launched, which broadcasted on two frequencies to calibrate ionosphere
group delay. It was proved from the TIMATION testing results that a system using a
passive-ranging technique, combined with highly accurate clocks, could provide the
basis for a new and revolutionary navigation system with three-dimensional coverage
throughout the world.
229
Chinese BeiDou navigation satellite system and European Galileo navigation satellite system, are four core providers designated by the International Committee on
Global navigation satellite system (ICG), and will be highlighted for their introductions in this section. In addition, the Japanese Quasi Zenith Satellite System (QZSS)
and the Indian Region Navigation Satellite System (IRNSS) are also developed by
using the single-way timing and ranging ways. Both the QZSS and IRNSS, which
are the regional navigation systems, can usually be found from the related references
for the interested readers, and are not going to be further described in this book.
4.6.3.1 GPS System
In 1960s, besides the Transit system, there were also three navigation satellite test
programs developed by the U.S. Forces. One was the Project 621B initiated by
the Space Division of the U.S. Air Force in 1963; the other was the TIMATION
program, which was conceived and developed by the Naval Center for Space Technology (NCST) at Naval Research Laboratory (NRL) in Washington D. C. beginning
in 1964; the third was the Sequential Collation of Range (SECOR) system developed by the U.S. Army, and the first SECOR satellite was launched for military
geodetic surveying in 1964.
The Project 621B’s proposal was presented originally by Ivan A. Getting
(1912−2003) who was then-president of the Aerospace Corporation. Seeing the
need for a new satellite-based navigation system, Ivan Getting envisioned a more
accurate positioning system that would be available in three dimensions, 24 h a
day, 7 days a week. At that time, Getting’s energy and foresight were essential to
gaining the Air Force support to study the system alternatives. In the Project 621B,
the passive-ranging technique was used to eliminate the need for an extremely stable
clock in the user equipment and provide three-dimensional positioning. Moreover,
the Code Division Multiple Access (CDMA) signal structure was also designed for
the satellites, and the prototype versions of CDMA navigation receivers were developed. Between 1968 and 1972, using the receiver on board of aircrafts to receive
from the ground-based pseudo-satellite signals, the Project’s tests were carried out
at White Sands Missile Range, New Mexico, to verify the feasibility of choosing
CDMA as the passive-ranging signal and other related techniques.
The core concept of TIMATION was a time-based navigation system with passive
ranging, circular orbits and space-borne high-precision clocks synchronized to a
master clock, presented by Roger L. Easton (1921−2014), a scientist and engineer at
the NRL. In May 1967, the first test satellite TIMATION-1 was launched successfully,
which was a small satellite with a weight of 38.3 kg and a power of 6 W, and its key
feature was to carry a very stable quartz clock. In September 1969, the TIMATION-2
satellite was launched, which broadcasted on two frequencies to calibrate ionosphere
group delay. It was proved from the TIMATION testing results that a system using a
passive-ranging technique, combined with highly accurate clocks, could provide the
basis for a new and revolutionary navigation system with three-dimensional coverage
throughout the world.