234
4 Navigations from Ground to Space
civilian users. According to the different performance improvements, the GPS III
satellites are divided into three types, namely, A, B and C, where the GPS IIIA delivers
significant improvements over current GPS satellites, including a new international
civil signal (L1C) and increased M-code anti-jam power with full Earth coverage
for military users; the GPS IIIB will enable a cross-linked command and control
architecture, allowing the satellites to be updated from a single ground station instead
of waiting for each satellite to orbit in view of a ground antenna; the GPS IIIC will
include a high-powered spot beam to deliver greater M-code power for increased
resistance to hostile jamming. The final GPS III satellite proves three times better
positioning accuracy and up to eight times improved anti-jamming capabilities, with
the navigation payload of 70% digital. As of April 2020, there are a total of 32
satellites in orbits for the GPS constellation, including 10 IIRs, 8 IIR-Ms, 12 IIFs
and 2 IIIs.
As deploying GPS III satellites to more resistant to jamming and spoofing, the U.S.
Air Force is currently looking for ways to shore up the PNT capabilities provided by
the GPS. One approach the Air Force believes feasible is to supplement its medium
Earth-orbiting GPS constellation with an additional layer of smaller satellites in
geosynchronous Earth orbit. To test that idea, the Air Force Research Laboratory in
2022 will launch an experimental PNT satellite, called NTS-3. Like its predecessors
the NTS-1 and NTS-2, the NTS-3 is revolutionary in its approach, addressing new
capabilities and paving the way to more resilient PNT. In the next few decades, it
will blaze the trail to unfettered access to the vital data that the GPS provides, even
in the midst of a wide variety of new threats [9].
4.6.3.2 GLONASS System
On the basis of implementing the Tsiklon, Parus and Tsikada navigation system
in practice, the Soviet government made a decision to launch the development
of the unified space navigation system, its second-generation navigation system
GLONASS, in 1976. The design proposal of the GLONASS was completed in the
late 1970s, using the constellation Walker24/3/2, with an orbital altitude of 19,130
km and an inclination of 64.8°. The GLONASS satellite’s orbits are the repeated
orbits, with a period of 17 circles per 8 days. The first-generation GLONASS satellites were 7.8-m tall, with the width of 7.2 m, measured across their solar panels,
and the weight of 1260 kg. By using the heavy-lift Proton rocket, three GLONASS
satellites would be launched at a time. The GLONASS satellites transmit two types
of navigation signals: one is an open standard-precision signal L1OF, and the other
is an obfuscated high-precision signal L1SF/L2SF.
In October 1982, the first three GLONASS satellites, respectively, designated
Cosmos-1413, Cosmos-1414 and Comos-1415, were successfully launched aboard
a Proton rocket. As only one GLONASS satellite (real Cosmos-1414) was ready in
time for the launch instead of the expected three, it was decided to launch it along
with two mock-ups, the dummies Cosmos-1413 and Cosmos-1415. Between 1982
and 1991, there were 43 GLONASS-related satellites plus 5 test satellites launched.
4 Navigations from Ground to Space
civilian users. According to the different performance improvements, the GPS III
satellites are divided into three types, namely, A, B and C, where the GPS IIIA delivers
significant improvements over current GPS satellites, including a new international
civil signal (L1C) and increased M-code anti-jam power with full Earth coverage
for military users; the GPS IIIB will enable a cross-linked command and control
architecture, allowing the satellites to be updated from a single ground station instead
of waiting for each satellite to orbit in view of a ground antenna; the GPS IIIC will
include a high-powered spot beam to deliver greater M-code power for increased
resistance to hostile jamming. The final GPS III satellite proves three times better
positioning accuracy and up to eight times improved anti-jamming capabilities, with
the navigation payload of 70% digital. As of April 2020, there are a total of 32
satellites in orbits for the GPS constellation, including 10 IIRs, 8 IIR-Ms, 12 IIFs
and 2 IIIs.
As deploying GPS III satellites to more resistant to jamming and spoofing, the U.S.
Air Force is currently looking for ways to shore up the PNT capabilities provided by
the GPS. One approach the Air Force believes feasible is to supplement its medium
Earth-orbiting GPS constellation with an additional layer of smaller satellites in
geosynchronous Earth orbit. To test that idea, the Air Force Research Laboratory in
2022 will launch an experimental PNT satellite, called NTS-3. Like its predecessors
the NTS-1 and NTS-2, the NTS-3 is revolutionary in its approach, addressing new
capabilities and paving the way to more resilient PNT. In the next few decades, it
will blaze the trail to unfettered access to the vital data that the GPS provides, even
in the midst of a wide variety of new threats [9].
4.6.3.2 GLONASS System
On the basis of implementing the Tsiklon, Parus and Tsikada navigation system
in practice, the Soviet government made a decision to launch the development
of the unified space navigation system, its second-generation navigation system
GLONASS, in 1976. The design proposal of the GLONASS was completed in the
late 1970s, using the constellation Walker24/3/2, with an orbital altitude of 19,130
km and an inclination of 64.8°. The GLONASS satellite’s orbits are the repeated
orbits, with a period of 17 circles per 8 days. The first-generation GLONASS satellites were 7.8-m tall, with the width of 7.2 m, measured across their solar panels,
and the weight of 1260 kg. By using the heavy-lift Proton rocket, three GLONASS
satellites would be launched at a time. The GLONASS satellites transmit two types
of navigation signals: one is an open standard-precision signal L1OF, and the other
is an obfuscated high-precision signal L1SF/L2SF.
In October 1982, the first three GLONASS satellites, respectively, designated
Cosmos-1413, Cosmos-1414 and Comos-1415, were successfully launched aboard
a Proton rocket. As only one GLONASS satellite (real Cosmos-1414) was ready in
time for the launch instead of the expected three, it was decided to launch it along
with two mock-ups, the dummies Cosmos-1413 and Cosmos-1415. Between 1982
and 1991, there were 43 GLONASS-related satellites plus 5 test satellites launched.