GPS - Hệ thống định vị toàn cầu

Cám ơn Digicams đã có lời khen. Hiện nay gps đang vi vu ở Sapa với máy thu GPS nên không có điều kiện post bài liên tục. Mong các bạn thông cảm
GPS

(Viết tiếp bài post ngày 17/12)
Để có thể đưa các ứng dụng GPS đến với chúng ta, các ký sư đã có một giải pháp thông minh và hiệu quả. Mỗi quả vệ tinh mang theo một cái đồng hồ nguyên tử, nhưng mỗi máy thu thì chỉ trang bị đồng hồ quartz thông thường. Các đồng hồ quartz này được điều chỉnh liên tục dựa vào tín hiệu được truyền đi từ các vệ tinh.
Trên lý thuyết thì 4 mặt cầu phải giao nhau tại 1 điểm. Nhưng do sai số đồng hồ quartz rẻ tiền, 4 mặt cầu đã không cho 1 giao điểm duy nhất. Biết rằng sai số này gây ra bởi đồng hồ trên máy thu là như nhau "t, máy thu có thể dễ dàng loại trừ sai số này bằng cách tính toán ra lượng hiệu chỉnh cần thiết để 4 mặt cầu giao nhau tại một điểm. Dựa vào đó, máy thu tự động điều chỉnh đồng hồ cho đồng bộ với đồng hồ nguyên tử trên vệ tinh. Nhờ đó mà đồng hồ trên máy thu có độ chính xác gần như tương đương với đồng hồ nguyên tử. Vậy là chuyện đo khoảng cách đã được giải quyết ổn thoả.
GPS

Biết khoảng cách rồi, chúng ta còn phải biết vị trí chính xác của các vệ tinh trên quĩ đạo. Điều này cũng không khó lắm vì các vệ tinh chuyển đông trên các quĩ đạo biết trước và có thể dự đoán được.Trong bộ nhớ của mỗi máy thu đều có chứa một bảng tra vị trí tính toán của tất cả các vệ tinh vào bất kỳ thời điểm nào gọi là Almanac. Lực hút của mặt trăng, mặt trời có ảnh hưởng nhất định làm thay đổi quĩ đạo của các vệ tinh một chút xíu nhưng bộ quốc phòng Mỹ liên tục theo dõi vị trí chính xác của các vệ tinh và truyền thông số hiệu chỉnh đến các máy thu thông qua tín hiệu từ vệ tinh.
GPS

Vậy là cả hai vấn đề khoảng cách và vị trí đã giải quyết xong, và hệ thống cơ bản hoạt động tốt, tuy nhiên, người ta nhận thấy hệ thống có nhiều sai số. Nguyên nhân đầu tiên là do việc giả sử rằng các tín hiệu vệ tinh được truyền theo đường thẳng đến các máy thu với vận tốc không đổi. Trong thực tế, bầu khí quyến trái đất ít nhiều làm chậm tốc độ truyền, đặc biết là khi sóng điên từ đi qua các tầng điện ly và đối lưu. Do tính chất của các tầng này khác nhau tại các vị trí khác nhau trên trái đất nên độ trễ này phụ thuộc vào vị trí của máy thu trên mặt đất, điều đó có nghĩa là khó có thể loại trừ sai số này. Gần đây người ta tạo ra các mô hình toán học mô phỏng tính chất của bầu khí quyển trái đát để giảm thiểu sai số này. Ngoài ra, khi tín hiệu phản xạ từ các vật thể lớn như các toà nhà cao tầng, cũng tạo cho máy thu một sai số như là đến từ một khoảng cách xa hơn. Thỉnh thoảng, tín hiệu từ các vệ tinh cũng có sai số. Bộ quốc phòng Mỹ cũng thêm vào sai số nhân tạo được gọi một cách văn hoa là Selective Availability hay SA.
GPS

Còn Rusian GLONASS bạn có trình bày nốt đi

Quá hay.
Tiếp đi bác.
.....Even if you don't love me... I believe...the love...that I give you... is enough for two.....

Qua các bài đã gửi, chúng ta đã thấy chức năng cơ bản nhất của máy thu GPS là thu nhận thông tin từ tối thiểu 4 vệ tinh, phối hợp các thông tin này với thông tin đã được chứa trong Almanac để tính toán ra vị trí của máy thu trên mặt đất. Một khi máy thu đã thu nhận và xử lý thông tin, máy sẽ cho chúng ta biết vĩ độ, kinh độ và cao độ của vị trí hiện thời. Để làm cho việc định vị thân thiện hơn, hầu hết các máy thu đều thể hiện các thông tin này dưới dạng các điểm trên bản đồ được chứa sẵn trong máy. Bạn có thể nối máy thu GPS với PC chứa bản đồ chi tiết. Một số máy thu còn cho phép nạp các bản đồ chi tiết vào bộ nhớ trong của máy hay kết nối với các thẻ nhớ đã nạp sẵn bản đồ.
Đây là thẻ nhớ của Garmin.
Còn Lowrance Ifinder của tớ dùng Multi Media Card (MMC) nhỏ bằng con tem bưu điện thôi. Dung lượng của MMC khoảng từ 8 - 128 MB.
GPS
Được gps sửa chữa / chuyển vào 21:34 ngày 30/12/2002

GLONASS = Global'naya Navigatsionnaya Sputnikovaya Sistema hay Global Navigation Satellite System
Hệ thống GLONASS của Nga cũng tương tự như GPS của Mỹ. Cả hai hệ thống đều dựa trên cùng những nguyên tắc truyền tín hiệu và định vị.
GLONASS có 21 vệ tinh (và 3 quả sơ cua) chuyển động trên 3 mặt phẳng quĩ đạo. Các mặt phẳng quĩ đạo cách nhau 120 độ và mỗi quả trên cùng mặt phẳng thì cách nhau 45 độ. Bán kính quĩ đạo khoảng 19,100 km với chu kỳ 11 giờ 15 phút.
Các trạm điều khiển mặt đất được bố trí rải rác trong phạm vi các nước thuộc Liên xô cũ. Vệ tinh GLONASS đầu tiên được phóng vào 1982. Theo kế hoạch ban đầu, hệ thống sẽ được đưa vào vận hành hoàn chỉnh vào 1991, nhưng trong thực tế, việc phóng các vệ tinh chỉ được hoàn thành vào cuối 1995 đầu 1996. Tổng thống Nga chính thức công bố GLONASS bắt đầu hoạt động vào 24 tháng 9 năm 1993.
Hệ thống Glonass đang hoạt động trong trạng thái ?odegraded? chỉ với 8 vệ tinh hoạt động. Do vậy mà khả năng "phủ sóng" trái đất không đwợc như GPS. Hình dưới đây cho thấy vao thời điểm khảo sát chỉ có phần trái đất gần với nam cực mới có thể "nhìn thấy" 4 quả.
Còn đây là độ "phủ sóng" của GPS
Nga đang có chương trình GLONASS-M hiện đại hoá hệ thống và các vệ tinh sẽ được phóng theo kế hoạch từ nay đến năm 2004. Các vệ tinh GLONASS-M sẽ cho chất lượng tín hiệu tốt hơn cũng như thời hạn hoạt động lâu hơn (7-8 năm thay vì 3 như hiện nay). Thế hệ thứ 3 được gọi là GLONASS-K cũng đang được nghiên cứu có thời hạn sử dụng lên tới 10 năm.
GLONASS do vận hành.
Được gps sửa chữa / chuyển vào 19:28 ngày 01/01/2003

GENERAL GLONASS
GLONASS (GLObal NAvigation Satellite System) is a satellite based radionavigation system which enables unlimited number of users to make all-weather 3D positioning, velocity measuring and timing anywhere in the world or near-Earth space .
õ? What is purpose GLONASS serves for?
õ? GLONASS performance.
õ? How does GLONASS work.
õ? GLONASS system components.
õ? GLONASS time.
õ? Differential GLONASS in Russia
What purposes GLONASS serves for?
õ? Air and naval traffic management, safety increasing;
õ? Geodesy and cartography;
õ? Ground transport monitoring;
õ? Time scale synchronisation of the remote from each other objects;
õ? Ecological monitoring, search and riscue operation organisation
The GLONASS system is managed for the Russian Federation
Government by the Russian Space Forces, system operator,
providing significant benefits to the civil users community
through a variety of applications. The GLONASS system has two
types of navigation signal: standard precision navigation signal
(SP) and high precision navigation signal (HP). SP positioning
and timing services are available to all GLONASS civil users on a
continuous, worldwide basis and provide the capability to obtain
horizontal positioning accuracy within 57-70 meters (99.7%
probability), vertical positioning accuracy within 70 meters
(99.7% probability), velocity vector components measuring
accuracy within 15 cm/s (99.7% probability) and timing accuracy
within 1 mks (99.7% probability). These characteristics may be
significantly increased using differential mode of navigation and
special methods of measurements (e.g. carrier phase etc.)
HOW DOES GLONASS WORKS
To make 3D positioning, velocity measuring and timing user of the
GLONASS use navigation radiosignales, continuously transmitted by
satellites. The each GLONASS satellite transmits two types of signal:
standard precision (SP) and high precision (HP). SP signal L1 have a
frequency division multiple access in L-band: L1= 1602MHz +
n0.5625MHz, where "n" is frequency channel number (n=0,1.2...). It
means that each satellite transmit signal on its own frequency which
differ from the one of other satellites. However some satellites have
the same frequencies but those satellites are placed in antipodal
slots of orbit planes and they have not appear at the same time in
user's view.
GLONASS receiver automatically receive navigational signals from
at least 4 satellites and measures their pseudoranges and velocities.
Simultaneously it select and process navigation message from
satellites signals. Computer of GLONASS receiver process all the input
data and calculate three coordinates, three components of velocity
vector, and precise time.
HOW DOES GLONASS WORKS
To make 3D positioning, velocity measuring and timing user of the
GLONASS use navigation radiosignales, continuously transmitted by
satellites. The each GLONASS satellite transmits two types of signal:
standard precision (SP) and high precision (HP). SP signal L1 have a
frequency division multiple access in L-band: L1= 1602MHz +
n0.5625MHz, where "n" is frequency channel number (n=0,1.2...). It
means that each satellite transmit signal on its own frequency which
differ from the one of other satellites. However some satellites have
the same frequencies but those satellites are placed in antipodal
slots of orbit planes and they have not appear at the same time in
user's view.
GLONASS receiver automatically receive navigational signals from
at least 4 satellites and measures their pseudoranges and velocities.
Simultaneously it select and process navigation message from
satellites signals. Computer of GLONASS receiver process all the input
data and calculate three coordinates, three components of velocity
vector, and precise time.
GLONASS CONSTELLATION
Fully deployed GLONASS Constellation is composed of 24 satellites in three orbital planes whose acsending nodes ares 120 degrees apart.
8 satellites are equally spaced in each plane with argument of latitude displacement of 45 degrees. Besides the planes themselves have 15 degrees argument of latitude displacement.
The each GLONASS satellite operates in circular 19100 km orbits at an inclination angle of 64.8 degrees and each satellite completes an orbit in approximately 11 hours 15 minutes. The spacing of satellites in orbits is arranged so that a minimum of 5 satellites are in view to users world-wide, with adequate geometry, i.e. GLONASS Constellation allows to provide continuous and global navigation coverage for performing of successful navigation observations.
The each GLONASS satellite transmits radiofrequency navigation signal containing navigation message for users.
GROUND-BASED CONTROL COMPLEX
The GLONASS Constellation is operated by Ground-based Control
Complex (GCS). It consists the System Control Center (Golitsyno-2,
Moscow region) and a several Command Tracking Stations (CTS) are
placed over a wide area of Russia. The CTSs track the GLONASS
satellites in view and accumulate ranging data and telemetry from the
satellites signals. The information from CTSs is processed at the SCC
to determine satellite clock and orbit states and to update the
navigation message of each satellite. This updated information is
transmitted to the satellites via the CTSs, which also used for
transmitting of control information.
The CTSs ranging data is periodically calibrated using a laser
ranging devices at the Quantum Optical Tracking Stations which are
within GCS. Each GLONASS satellite specially carries laser reflectors
for this purpose.
The synchronization of all the processes in the GLONASS system is
very important for its proper operability. There is the Central
Synchronizer within GCS to meet this requirement. The Central
Synchronizer is high-precise hydrogen atomic clock which forms the
GLONASS system time scale. The onboard time scales ( on a basis of
satellite cesium atomic clocks) of all the GLONASS satellites are
synchronized with the State Etalon UTC(CIS) in Mendeleevo, Moscow
region, through the GLONASS System Time scale.
GLONASS SYSTEM TIME
The GLONASS satellites are equippped with cesium clocks, daily
frequency instabilities of which are no more than 5x10E(-13). This
provides an accuracy of satellite time synchronization relative to
GLONASS System Time of about 15 nanoseconds (one sigma) , with clocks
corrections uploaded to the satellite twice a day.
GLONASS System Time (GLONASST) is generated on the basis of
Central Synchronizer time. Daily instabilities of Central Synchronizer
hydrogen clocks are no more than 5x10E(-14). GLONASST shift relative
to UTC(CIS) should be less than 1 millisecond. The accuracy of the
shift should be less than 1 microsecond.
It is well-known that the fundamental time scale for all the
earth time-keeping is International Atomic Time (TAI). It results from
analyses by the Bureau International de l'Heure (BIH) in Paris of data
from atomic standards of many countries. The fundamental unit of TAI
is the SI second, defined as "the duration of 9 192 631 770 periods of
the radiation corresponding to the transition between two hyperfine
levels of the ground state of the cesium 133 atom".
Because TAI is a continuous time scale, it has one fundamental
probleme in practical use: the earth's rotation with respect to the
sun is slowing down by a variable amount which averages, at present
about 1 second per year. Thus TAI would eventually become
inconveniently out of synchronization with the solar day. This problem
has been overcome by introducing UTC, which runs at the same rate as
TAI but is incremented by 1 second jumps ("leap seconds") when
necessary, normally at the end of June or December of each year.
It i also well-known that each of the world's time centers keeps
a local realization of UTC, the epoch and rate of which relative to
UTC(BIH) are monitored and corrected periodically. UTC(CIS) is
maintained by the Main Metrological Center of Russian Time and
Frequency Service (VNIIFTRI) at Mendeleevo, Moscow region.
When UTC is incremented by leap seconds, GLONASST is incremented
too. Therefore, there is no integer-second difference between GLONASST
and UTC. However there is a constant offset of three hours between
GLONASST and UTC(CIS) due to GLONASS monitoring specific features.
GLONASST = UTC+03h.00min.
As for GPS, GPS System Time (GPST) is not incremented by leap seconds,
and there is the integer-second difference between GPST and UTC.
GPST-UTC = +10 s and TAI-UTC = +29 s (at the time of writing).
And at any instant: GPST + 19 s = TAI.
COORDINATE REFERENCE SYSTEM PZ-90
The GLONASS ephemerides are computed in ECEF (earth-centred,
earth-fixed) coordinate reference system PZ-90 (PZ - parameters of
Earth). The parameters of common terrestrial ellipsoid for PZ-90 are:
a = 6378136 m, f = 1:298.257839303.
At present a parameters of transformation from PZ-90 to WGS-84
are not yet definitively estimated.

DIFFERENTIAL GLONASS IN RUSSIA
In Russia, an active research in the field of differential
GLONASS system was begun in the end of the seventies, that is
practically at the same time when GLONASS itself had been developed.
The scientists of Central Research Institute of the Russian Space
Forces (TsNII VKS), Russian Research Institute of Space Device
Engineering (RNII KP), Scientific Producting Corporation of Applied
Mechanics (NPO PM) took active part in these research works.
However, owing to various objective causes an implementation of
differential GLONASS in Russia was dragged on. A lack of the Selective
Availability mode in GLONASS played a not unimportant role in the
process. The standard accuracy of GLONASS on the few ten meters level
met the requirements of common users in Russia.
But the works in this field had been speeded up in 1990-1991. It
should be noted that the operating zones of some foreign DGPS networks
are partly spreading over the Russian territories and aquatories.
Besides, a some foreign companies are displaying the great interest in
penetration to the Russian market of users equipment, and in
deployment of its own differential systems in Russia.
Under these circumstances, an interest of Russian users and users
equipment manufacturers in differential mode of navigation are
increasing. Therefore, the works on creation of differential stations
for various applications had been speeded up.
At present, there are the plans of creation of local-area and
regional-area differential system for air traffic control and vessels
traffic services. Taking into account its departmental specialization
caused, on the whole, by channels selected for differential
corrections transmission, the use of these systems by common users is
problematical. Therefore, it should be expected on the appearance of
intentions to create others differential systems in the future, e.g.
for the sake of surface transportation control.
Thus, it can be noted there is the tendency to create the Russian
network of departmental differential systems oriented towards
specified users. These systems are a local-area differential systems
(LADS), and its operating zones do not cover all the Russian
territory. The way of differential systems deployment realized by the
simple increasing of LADS number is too hard justified from the
standpoint of economics. That is why the other way of differential
system deployment was proposed.
In 1994, Central Research Institute of the Russian Space Forces
jointly with Coordinational Scientific Information Center of the
Russian Space Forces (KNITs VKS) developed a project of the future
Russian differential system with the use of ground-based
infrastructure of the Russian space vehicles control complex. This
differential system will be able to serve practically all the GLONASS
users in Russia.
Principles of operation of this system and algorithms of
differential corrections calculation and formation were formerly
developed and examined using as measuring data from GLONASS
ground-based control complex, as results of TsNII VKS/KNITs
VKS/Russian Maritime Geodetic Company joint works in Far-East and
South-East Asia regions.
The analysis of domestic and foreign situation concerning
differential systems development performed by TsNII in 1994 clearly
indicated that an isolated development of WADS and LADS do not meet
up-to-date requirements. In order to co-ordinate the development of
detached differential systems in Russia and its subsequent integration
within United (State) differential system (UDS), the Concept of
differential GLONASS system design had been assigned to develop.
Interdepartmental resolution "On executing works in different-level
differential systems and integrity monitoring system development" from
1994, contains this assignement. The Concept was developed by the
Russian Space Forces (VKS) jointly with the Russian Space Agency (RKA)
and the Ministry of Transport. At present, the first version of the
document is on the approvement at concerned ministries and
departments.
UDS CONCEPT
The Concept determine that the Russian differential system will
have the three-level hierarchic structure including WADS,RADS and
LADS. Each level of UDS is the autonomous system performing its own
tasks. In the aggregate, the system are united system providing the
users with the precise navigation service.
The first level of the UDS is the wide-area differential system
WADS which provides;
- collecting and processing of data received from monitoring
stations, 2nd- and 3rd-level differential stations in order to
promptly correct the parameters of regional ionosphere model, and
GLONASS ephemerides, clock corrections and integrity data;
- tranmissions of needed WADS data to 2nd- and 3rd-level
differential stations or directly to users;
- interaction between the WADS and the GLONASS Control Center
(navigation field monitoring division).
The required number of the 1st-level differential stations is
from three to five. Each of the stations is the WADS Center. The
accuracy of positioning provided within the 1500-2000 km area is from
5 to 10 meters.
By our opinion, the arrangement of 1st-level differential
stations network is possible on a basis of existing infrastructure of
Russian space vehicles control complex which contain the ground-based
control complex sites, data interchange systems and a powerful
computation facilities.
The following circumstances are propitious for this idea: - the
ground-based elements of the Russian space vehicles control
complex are placed over a wide area of all the Russia , allowing to
create the full coverage by differential service of main Russian
regions;
- the infrastructure of the Russian space vehicles control
complex have the excellent capabilities to collect and process
navigation data from many sites;
- the most simple way to arrange an interaction between GLONASS
Control Complex and differential system facilities is to do it within
the WADS. And the WADS will use the data from RADS and LADS.
The second level of UDS is regional-area differential system RADS
(specialized differential system), which will be created in order to
cover the highly developed regions having a powerful economics and a
great many users. The RADS can be deployed in areas of an intensive
traffic (air, maritime, surface, railway), complicated meteo
con***ions, and where the surveying is performing, etc.
The accuracy of positioning provided by 2nd-level differential
station within the 500 km area is from 3 to 10 m.
The third level of the UDS is the LADS which will be deployed in
detached regions in order to provide a particular economic, scientific
or defence applications. The LADS will be able also provide the
performing of special (episodical) departmental works, including the
post-processing of data. The precise LADS will be able to provide
within the few tens of kilometers area the decimeter level of
positioning accuracy.
The LADS can be also created in a mobile version. 3rd-level
differential systems may contain the pseudolites.
The terms and stages of the Russian differential system creation
depend on many factors. However, it may be expected the Russian RADS
and LADS will be actively deployed in 1996-1997, then they will be
integrated into the UDS in 1998-2000. The UDS will use the
capabilities of infrastructure of the Russian space vehicles control
complex.
GLONASS history
Block No. GLONASS No.
(slot/frequency) Cosmos No. Launch
date Put into
operation End of
Operation (Withdrawn)
1 224 (01/--) 1413 12.10.82 15.10.82 12.01.84 (16.04.84)
2 222 (03/--) 1490 10.08.83 03.09.83 05.07.84 (31.10.85)
2 223 (02/--) 1491 10.08.83 31.08.83 27.09.84 (09.06.88)
3 220 (18/--) 1519 29.12.83 07.01.84 27.09.84 (28.01.88)
3 219 (17/--) 1520 29.12.83 15.01.84 30.06.86 (16.09.86)
4 218 (19/--) 1554 19.05.84 13.06.84 16.08.85 (16.09.86)
4 217 (18/--) 1555 19.05.84 18.06.84 25.10.85 (17.09.87)
5 216 (02/10) 1593 04.09.84 22.09.84 28.11.85 (19.05.88)
5 215 (03/--) 1594 04.09.84 28.09.84 04.09.86 (16.09.86)
6 224 (01/--) 1650 18.05.85 28.06.85 08.11.85 (29.11.85)
6 221 (01/07) 1651 18.05.85 14.06.85 09.08.87 (17.09.87)
7 209 (18/04) 1710 25.12.85 24.01.86 28.02.87 (16.03.89)
7 210 (17/19) 1711 25.12.85 24.01.86 16.05.87 (16.09.87)
8 203 (02/11) 1778 16.09.86 19.10.86 20.02.87 (13.07.89)
8 202 (03/20) 1779 16.09.86 19.10.86 15.07.88 (24.10.88)
8 201 (08/22) 1780 16.09.86 19.10.86 15.06.88 (10.10.88)
9 - 1838 24.04.87 Failed launch
9 - 1839 24.04.87 Failed launch
9 - 1840 24.04.87 Failed launch
10 229 (--/--) 1883 16.09.87 12.10.87 06.06.87 (03.07.89)
10 228 (--/--) 1884 16.09.87 12.10.87 30.08.88 (15.12.88)
10 227 (17/--) 1885 16.09.87 07.10.87 01.02.89 (09.03.89)
11 - 1917 17.02.88 Failed launch
11 - 1918 17.02.88 Failed launch
11 - 1919 17.02.88 Failed launch
12 235 (07/--) 1946 21.05.88 15.06.88 10.05.90 (22.10.90)
12 234 (08/--) 1947 21.05.88 15.06.88 19.03.91 (18.09.91)
12 233 (01/--) 1948 21.05.88 15.06.88 11.06.91 (18.09.91)
13 238 (17/--) 1970 16.09.88 11.10.88 21.05.90 (22.10.90)
13 237 (18/--) (1) 1971 16.09.88 11.10.88 31.08.89 (30.11.89)
13 236 (19/--) (2) 1972 16.09.88 11.10.88 01.11.91 (12.08.92)
14 239 (02/09) 1987 10.01.89 01.02.89 14.03.93 (03.02.94)
14 240 (03/06) 1988 10.01.89 01.02.89 16.02.92 (02.06.92)
14 241 1989 10.01.89 Geodetic reference satellite
15 231 (24/--) 2022 31.05.89 04.07.89 25.01.90 (13.03.90)
15 230 (19/--) 2023 31.05.89 17.06.89 18.11.89 (13.03.90)
15 232 2024 31.05.89 Geodetic reference satellite
16 242 (17/21) 2079 19.05.90 20.06.90 23.04.94 (17.08.94)
16 228 (19/03) 2080 19.05.90 17.06.90 27.07.94 (27.08.94)
16 229 (20/15) 2081 19.05.90 11.06.90 18.08.92 (20.01.93)
17 247 (07/13) 2109 08.12.90 01.01.91 17.03.94 (10.06.94)
17 248 (04/14) 2110 08.12.90 29.12.90 29.10.93 (20.01.94)
17 249 (05/19) (4) 2111 08.12.90 28.12.90 09.06.96 (15.08.96)
18 750 (22/11) 2139 04.04.91 28.04.91 29.09.94 (14.11.94)
18 753 (21/20) 2140 04.04.91 28.04.91 06.01.92 (04.06.93)
18 754 (24/14) 2141 04.04.91 04.05.91 26.02.92 (16.06.92)
19 768 (03/22) 2177 30.01.92 24.02.92 09.01.93 (29.06.93)
19 769 (08/02) 2178 30.01.92 22.02.92 23.05.97 (24.06.97)
19 771 (01/17) (3) 2179 30.01.92 18.02.92 25.10.86 (21.12.96)
20 756 (18/24) (6) 2204 30.07.92 19.08.92 27.06.97 (05.08.97)
20 772 (21/08) 2205 30.07.92 29.08.92 29.06.94 (27.08.94)
20 774 (24/01) 2206 30.07.92 25.08.92 18.05.96 (26.08.96)
21 773 (02/05) 2234 17.02.93 14.03.93 09.03.94 (17.08.94)
21 759 (06/23) (5) 2235 17.02.93 25.08.93 30.06.97 (05.08.97)
21 757 (03/12) 2236 17.02.93 14.03.93 27.07.97 (23.08.97)
22 758 (18/10) 2275 11.04.94 04.09.94 Operational
22 760 (17/24) 2276 11.04.94 18.05.94 30.07.99 (09.09.99)
22 761 (23/03) 2277 11.04.94 16.05.94 24.07.97 (29.08.97)
23 767 (12/22) (7) 2287 11.08.94 07.09.94 05.11.98 (03.02.99)
23 770 (14/09) 2288 11.08.94 04.09.94 Operational
23 775 (16/22) 2289 11.08.94 07.09.94 Operational
24 762 (04/12) (7) 2294 20.11.94 11.12.94 04.09.99 (19.11.99)
24 763 (03/21) 2295 20.11.94 15.12.94 27.07.99 (05.10.99)
24 764 (06/13) 2296 20.11.94 16.12.94 27.10.99 (30.11.99)
25 765 (20/01) 2307 07.03..95 30.03.95 10.09.99 (19.11.99)
25 766 (22/10) 2308 07.03.95 05.04.95 Operational
25 777 (19/03) 2309 07.03.95 05.04.95 17.07.97 (26.12.97)
26 780 (15/04) 2316 24.07.95 26.08.95 03.12.98 (06.04.99)
26 781 (10/09) 2317 24.07.95 22.08.95 Operational
26 785 (11/04) 2318 24.07.95 22.08.95 Operational
27 776 (09/06) 2323 14.12.95 07.01.96 Operational
27 778 (15/11) (8) 2324 14.12.95 26.04.99 Operational
27 782 (13/06) 2325 14.12.95 18.01.96 Operational
28 779 (01/02) 2364 30.12.98 18.02.99 Operational
28 784 (08/08) 2363 30.12.98 29.01.99 Operational
28 786 (07/07) 2362 30.12.98 29.01.99 Operational
Notes: (1) On 6 August 1989 SV 237 had been moved from slot 18 to slot 20
(2) On 5 August 1989 SV 236 had been moved from slot 19 to slot 18
(3) On 2 September 1992 frequency channel of SV 771 had been changed from 17 to 23
(4) On 2 September 1992 frequency channel of SV 249 had been changed from 19 to 23
(5) On December 1994 SV 759 had been moved from slot 6 to slot 7and on 2 September 1993 frequency channel of SV 771 had been changed from 23 to 21
(6) SV 756 had been moved from slot 18 to slot 21
(7) On 27 September 1994 frequency channels of both SV 767 and SV 775 had been changed from 21 to 22
(8) On April 1999 SV 778 had been moved from slot 09 to slot 15