[FPSPACE] PRC'S YUANWANG OCEANGOING INSTRUMENT SHIP

[JamesOberg@aol.com]

PRC'S YUANWANG OCEANGOING INSTRUMENT SHIP
BEIJING ZHONGGUO HANGTIAN (AEROSPACE CHINA) IN CHINESE 01 JUL 00 PP 11-13

   [ARTICLE BY WEN YU: "THE MAGNIFICENT LEGACY BEING FORGED BY THE
YUANWANG CLASS SHIPS"]
     THE YUANWANG CLASS OF OCEANGOING
MEASURING SHIPS ARE SEABORNE MOBILE MEASURING SHIPS THAT ARE A PART
OF THE CHINESE AEROSPACE TRACKING AND CONTROL NETWORK. THESE
MEASURING SHIPS HAVE MADE 34 VOYAGES OVER THE PAST 20 YEARS,
NAVIGATING A TOTAL OF NEARLY 600 THOUSAND NAUTICAL
MILES--EQUIVALENT TO CIRCLING THE EARTH 22 TIMES. THEY HAVE CARRIED
OUT 36 OCEANGOING ASSIGNMENTS RELATING TO DOMESTIC AND FOREIGN 
SATELLITE LAUNCHES AND/OR MAJOR NATIONAL SCIENTIFIC RESEARCH
EXPERIMENTS. THE TRACKING AND CONTROL MISSION SUCCESS RATE IS
100%--A WONDERFUL ACHIEVEMENT IN THE HISTORY OF INTERNATIONAL
AEROSPACE TRACKING AND CONTROL. THE YUANWANG CLASS OF MEASURING
SHIPS ARE A PART OF THE AEROSPACE TRACKING AND CONTROL NETWORK.
THEY CAN TRACK AND MEASURE THE FLIGHT TRAJECTORIES OF SPACECRAFT
AND ROCKETS, RECEIVE TELEMETRY INFORMATION AND SEND REMOTE
COMMANDS. IN THE FUTURE, THEY WILL ALSO BE ABLE TO CARRY OUT
COMMUNICATIONS WITH ASTRONAUTS AND RESCUE RETURNING ASTRONAUTS THAT
HAVE SPLASHED DOWN, ETC.

    AEROSPACE TRACKING AND CONTROL IS EXTENDED TO THE OCEANS

    THE RANGE OF THE WORLD'S FIRST SHORT-RANGE LAUNCH VEHICLE WAS
ONLY A FEW HUNDRED KILOMETERS. A RADAR INSTALLATION ON THE GROUND
WAS SUFFICIENT TO COMPLETE TRACKING AND MEASURING TASKS THROUGHOUT
THE ENTIRE RANGE OF SUCH A LAUNCH VEHICLE. WITH THE DEVELOPMENT OF
AEROSPACE TECHNOLOGY, LONG-RANGE LAUNCH VEHICLES AND SATELLITES
CAME ON THE SCENE. THEIR FLIGHT COURSES EXTENDED AS FAR AS SEVERAL
TENS OF THOUSANDS OF KILOMETERS. TRACKING AND CONTROL STATIONS IN 
CHINA WERE UNABLE TO MEET TRACKING AND MEASURING NEEDS FOR THESE
SPACECRAFT THROUGHOUT THE ENTIRE COURSE OF FLIGHT. THUS, MOBILE
SEABORNE AEROSPACE MEASURING SHIPS WERE BORN. A MEASURING SHIP
SERVES AS A MOBILE, SEABORNE TRACKING AND CONTROL STATION. IT CAN 
BE FLEXIBLY DEPLOYED IN THE ATLANTIC, PACIFIC AND/OR INDIAN OCEANS
IN ACCORDANCE WITH DEMANDS POSED BY ORBITAL COVERAGE AND
COMMUNICATIONS COVERAGE, THUS GIVING FULL PLAY TO ITS USEFUL
EFFICIENCY.

    THE U.S., THE FORMER SOVIET UNION AND FRANCE WERE THE COUNTRIES
TO FIRST USE MEASURING SHIPS TO TRACK AND MEASURE SPACECRAFT
[ORBITS]. THE U.S., BY VIRTUE OF ITS SUPERIOR ECONOMIC DEVELOPMENT
AND ITS OVERSEAS COLONIES, HAS BUILT NUMEROUS GROUND STATIONS ALL
ALONG THE ISLANDS OF THE PACIFIC OCEAN IN ACCORDANCE WITH ITS
MEASURING NEEDS. DESPITE THIS FACT, THE U.S. HAS, IN ADDITION,
DEPLOYED A NUMBER OF MEASURING SHIPS IN NECESSARY LOCATIONS.
HOWEVER, THE NUMBER THAT THE U.S. HAS DEPLOYED IS SOMEWHAT LESS
THAN THE NUMBER OF MEASURING SHIPS THAT HAVE BEEN DEPLOYED BY THE
FORMER SOVIET UNION. THE FORMER SOVIET UNION'S TERRITORY SPANS AN 
EXTREMELY LARGE DISTANCE, SPANNING LINES OF LONGITUDE THROUGH
ALMOST 180 DEGREES. IN ADDITION TO HAVING BUILT NUMEROUS GROUND
STATIONS ON ITS OWN TERRITORY, THE FORMER SOVIET UNION HAS ALSO
BUILT A LARGE NUMBER OF MEASURING SHIPS WHICH HAVE BEEN SPREAD OVER
THE ATLANTIC AND PACIFIC OCEANS. THE GREATEST NUMBER OF MEASURING
SHIPS EVER DEPLOYED BY THE FORMER SOVIET UNION AT ONE TIME IS 17.
THE LARGEST AEROSPACE MEASURING SHIP IN THE WORLD IS THE FORMER
SOVIET UNION'S GAGARIN CLASS, WHICH WEIGHS OVER 40 THOUSAND METRIC
TONS. FRANCE HAS MANY ISLANDS IN THE INDIAN OCEAN AND THE CARIBBEAN 
SEA THAT FACILITATE THE IMPLEMENTATION OF A WORLDWIDE NETWORK.
HOWEVER, FRANCE ALSO HAS MANY OF ITS OWN MEASURING SHIPS.

    LET US NOW LOOK AT MATTERS FROM THE STANDPOINT OF THE ACTUAL
SITUATION IN CHINA. ALTHOUGH THE LAND AREA OF CHINA IS 9.6 MILLION 
SQUARE KILOMETERS, THE SPAN FROM EAST TO WEST IS JUST A LITTLE OVER
4000 KILOMETERS AND THE SPAN FROM NORTH TO SOUTH IS JUST A LITTLE
OVER 2000 KILOMETERS. IF WE WANT TO TRACK SPACECRAFT THROUGHOUT THE
ENTIRE COURSE OF FLIGHT, RELYING ON BUILDING GROUND STATIONS ON OUR
LIMITED NATIONAL TERRITORY IS CLEARLY INADEQUATE. IN PARTICULAR,
WHEN IT IS NECESSARY TO IMPLEMENT CONTROL OF A SPACECRAFT'S REENTRY
POINT, THE SPACECRAFT IS OFTEN ON THE OTHER SIDE OF THE EARTH WHEN 
CONTROL OF THE SPACECRAFT AND ADJUSTMENTS OF THE SPACECRAFT'S
ATTITUDE ARE IMPLEMENTED FROM A REMOTE LOCATION. THUS IT IS
NECESSARY TO HAVE MEASURING STATIONS OUTSIDE OF OUR NATIONAL
TERRITORY.

    IN 1965, PREMIER ZHOU ENLAI PROPOSED THE GRAND CONCEPT OF CHINA
DEVELOPING ITS OWN OCEANGOING AEROSPACE MEASURING SHIPS. IN 1968,
CHAIRMAN MAO ZEDONG PERSONALLY APPROVED THE PLAN TO DEVELOP
OCEANGOING AEROSPACE MEASURING SHIPS. AFTER PASSING THROUGH THE
STORMS OF THE CULTURAL REVOLUTION, THE YUANWANG 1 AND YUANWANG 2
MEASURING SHIPS WERE FINALLY PUT INTO THE WATER ON AUG. 31, 1977
AND SEP. 1, 1978, RESPECTIVELY. THIS MARKED THE END OF THE PERIOD
IN WHICH CHINA WAS UNABLE TO MEASURE LAUNCH VEHICLE AND SATELLITE
[ORBITS] FROM OUTSIDE ITS NATIONAL TERRITORY. YUANWANG 1 AND
YUANWANG 2 CARRIED OUT MEASURING ASSIGNMENTS FOR THE FIRST TIME IN 
MAY OF 1980, WITH COMPLETE SUCCESS. SUBSEQUENTLY, THE TWO SHIPS
SUCCESSFULLY COMPLETED MEASURING ASSIGNMENTS RELATING TO CHINA'S
OWN INDEPENDENTLY DESIGNED AND DEVELOPED TEST COMMUNICATIONS
SATELLITE AND THE THIRD STAGE OF ITS LAUNCH VEHICLE. IN ORDER TO
ADAPT TO THE NEEDS OF INTERNATIONAL COMMERCIAL LAUNCHES, YUANWANG 1
AND YUANWANG 2 BOTH UNDERWENT TECHNICAL RECONSTRUCTIONS IN 1986.
THIS SERVED TO MARKEDLY ENHANCE THE OVERALL TECHNICAL PERFORMANCE
OF THEIR SYSTEMS AND TO ENHANCE THEIR COMPATIBILITY CAPABILITIES ON 
THE DOMESTIC AND INTERNATIONAL FRONTS. DURING THE LAUNCH ASSIGNMENT
FOR THE ASIASAT-1, THE YUANWANG CLASS MEASURING SHIPS UTILIZED
SHORT ARC MEASUREMENT DATA FROM THE ORBIT INJECTION PHASE TO
DETERMINE THE INITIAL ORBITAL ELEMENTS, AND MET THE REQUIREMENTS OF
THE SATELLITE USERS. THE MEASUREMENT ACCURACY OF THE YUANWANG SHIPS
WAS EQUIVALENT TO THE ACCURACY OF THE LONG ARC PRECISION ORBITS
THAT WERE MEASURED AT THE GROUND TRACKING AND CONTROL STATIONS OF
THE U.S. HUGHES CORPORATION. MEASURING SHIPS PLAYED AN IMPORTANT
ROLE IN CHINA'S FIRST COMMERCIAL LAUNCH. YUANWANG 3 WAS BUILT IN 
THE 1990'S. YUANWANG 4 WAS CONVERTED FROM THE FORMER STATE
OCEANOGRAPHY BUREAU'S XIANGYANGHONG 10 SHIP IN 1998.

    CHINA'S AEROSPACE MEASURING SHIPS ARE SEABORNE MOBILE MEASURING
STATIONS THAT ARE A PART OF THE AEROSPACE TRACKING AND CONTROL
NETWORK. THEY CAN BE DEPLOYED AT SUITABLE MARITIME LOCATIONS BASED
ON TRACKING AND CONTROL NEEDS AND THE FLIGHT TRACKS OF SPACECRAFT
AND LAUNCH VEHICLES. UNDER THE DIRECTION OF THE SPACECRAFT FLIGHT
CONTROL CENTER, THESE SHIPS TRACK AND MEASURE THE FLIGHT
TRAJECTORIES OF SPACECRAFT, RECEIVE TELEMETRY INFORMATION, SEND
REMOTE COMMANDS, COMMUNICATE WITH ASTRONAUTS AND RESCUE RETURNING
ASTRONAUTS THAT HAVE SPLASHED DOWN, ETC.

    SUPPLEMENTING LAND MEASUREMENTS

    THE YUANWANG MEASURING SHIPS ARE AN IMPORTANT COMPONENT PART OF
THE ENTIRE AEROSPACE TRACKING AND CONTROL NETWORK. THEY REPRESENT
AN IMPORTANT SUPPLEMENTARY MEASURE TO REMEDY SHORTCOMINGS IN THE
MEASURING CAPABILITIES OF CHINA'S GROUND STATIONS. SINCE OCEANS
OCCUPY 70% OF THE AREA OF THE ENTIRE GLOBE, A VAST AREA IS
AVAILABLE FOR SEABORNE AEROSPACE MEASURING ACTIVITIES AND A
MEASURING SHIP CAN REACH VIRTUALLY ANY MARITIME AREA. CURRENTLY,
MEASURING SHIPS ARE USED TO CARRY OUT MEASURING AND CONTROL TASKS
FOR THE GREAT MAJORITY OF THE SATELLITES THAT CHINA HAS LAUNCHED.
MEASURING SHIPS TAKE PART IN TRACKING AND CONTROL DUTIES FOR ALL OF
THE EARTH-SYNCHRONOUS SATELLITES WITH GEOSTATIONARY ORBITS THAT
CHINA HAS LAUNCHED (INCLUDING FOREIGN SATELLITES THAT HAVE BEEN 
LAUNCHED ON A COMMERCIAL BASIS). UNDER NORMAL CONDITIONS, WHEN THE
ANGLE OF INCLINATION OF GEOSTATIONARY SATELLITES LAUNCHED AT THE
XICHANG SATELLITE LAUNCH CENTER IS MORE THAN 20 DEGREES UPON 
INJECTION INTO ORBIT, A VERY LONG PERIOD OF TIME ELAPSES BETWEEN 
THE LAUNCH OF THE SATELLITE AND THE TIME IT REACHES ITS FINAL FIXED
POINT. OFTEN WHEN WE DEVISE MEANS TO "SEE" THE SATELLITE, IT IS
NECESSARY FOR MEASURING SHIPS TO TRACK AND CONTROL IT. IN ADDITION,
BECAUSE OPERATING TIME FOR THE LAUNCH VEHICLE IS COMPARATIVELY
LONG, IT IS PARTICULARLY NECESSARY FOR MEASURING SHIPS TO PROVIDE
ACCURATE ORBITAL PARAMETERS TO DETERMINE WHETHER TO PERFORM AN 
INTERMEDIATE SHUT DOWN AND REFIRE, AND TO DETERMINE WHETHER THE
ORBIT INJECTION PHASE AND ROCKET SEPARATION HAVE PROCEEDED
NORMALLY, WITH THE SATELLITE ACCURATELY INJECTED INTO ORBIT. IF
THERE IS AN ERROR IN THE SATELLITE'S ORBIT, IT IS ALSO NECESSARY
FOR THE MEASURING SHIP TO ISSUE COMMANDS SO AS TO CORRECT THE ERROR
IN A TIMELY MANNER. IN REGARD TO COMMERCIAL LAUNCHES, WE ONLY NEED
PROVIDE PERTINENT SEPARATION POINT PARAMETERS. WHEN LAUNCHING A
DOMESTIC SATELLITE, HOWEVER, DURING THE FIRST REVOLUTION OF
SATELLITE OPERATION THE MEASURING SHIP MUST ALSO CARRY OUT A SERIES
OF CONTROL OPERATIONS, SUCH AS DEPLOYING THE SATELLITE-BORNE SOLAR
PANELS AND ANTENNAS, ETC. IN ADDITION, THE MEASURING SHIP MUST
CARRY OUT PROCESSING VIS-A-VIS THE SATELLITE'S WORKING CONDITIONS,
ETC. IN THE CASE OF SOME SATELLITES, THE MEASURING SHIP MUST ALSO
IMPLEMENT DATA INPUT. SOMETIMES, MALFUNCTIONS OCCUR AFTER SATELLITE
LAUNCH, REQUIRING THE MEASURING SHIP TO ANALYZE AND ASSESS THE
SATELLITE'S CONDITION IN ORDER TO ADOPT EMERGENCY MEASURES IN A
TIMELY MANNER.

    CHINA'S SHIPS ARE UNIQUE IN BEING ABLE TO CARRY OUT CONTROL
ASSIGNMENTS

    CHINA'S MEASURING SHIPS DIFFER FROM FOREIGN MEASURING SHIPS. IN 
THE FIRST PLACE, CHINA'S MEASURING SHIPS REALLY HAVE DISTINCTIVE
CHINESE CHARACTERISTICS. THESE ARISE FROM CHINA'S SPECIFIC
CONDITIONS. AS WE HAVE SAID, CHINA DOES NOT HAVE TERRITORY OVERSEAS
AND CANNOT BUILD GROUND STATIONS ABROAD. ANOTHER POINT IS THAT, ON 
THE WHOLE, CHINA IS NOT VERY DEVELOPED ECONOMICALLY, AND CANNOT
BUILD A LARGE NUMBER OF MEASURING SHIPS AS OTHER COUNTRIES DO. AS A
RESULT, OUR MEASURING SHIPS HAVE GONE A ROUTE WITH UNIQUELY CHINESE
CHARACTERISTICS. THE NUMBER OF SUCH SHIPS IS SMALL. THEY HAVE
COMPREHENSIVE CAPABILITIES AND ONE SHIP SERVES MANY FUNCTIONS. THE
SHIPS CAN ADAPT TO MEASURING ASSIGNMENTS FOR VARIOUS SPACECRAFT
MODELS WITH VARIOUS ORBITS. IN REGARD TO THE SYSTEM OF ORGANIZATION 
AND SCHEME FOR MEASUREMENT [OPERATIONS], CHINA IS ALSO VERY
DIFFERENT FROM OTHER COUNTRIES. THE QUALITY OF CHINA'S TRACKING AND
CONTROL REACHES ADVANCED INTERNATIONAL LEVELS AND WE CAN COMPLETE A
NUMBER OF COMPLEX TRACKING AND CONTROL ASSIGNMENTS, INCLUDING
TRACKING AND CONTROL OF VARIOUS TYPES OF SATELLITES AND OF THE
"SHENZHOU" SPACECRAFT. THE TECHNICAL DIFFICULTIES ASSOCIATED WITH
USING MEASURING SHIPS FOR CONTROL ARE COMPARATIVELY GREAT, WITH A
NUMBER OF COMPLEX TECHNICAL PROBLEMS. WE HAVE SOLVED ALL OF THESE
PROBLEMS VERY SATISFACTORILY. FOR ALL INTENTS AND PURPOSES, WE CAN 
ACCOMPLISH BOTH MEASURING AND CONTROL ASSIGNMENTS WITH JUST ONE
SHIP. THIS IS VERY RARELY SEEN ON THE INTERNATIONAL STAGE; ONLY
CHINA HAS THIS KIND OF SETUP. DUE TO MUTUAL INTERFERENCE BETWEEN 
THE VARIOUS TYPES OF ELECTRONIC EQUIPMENT ON A SHIP, THE ACCURACY
OF SHIPS ON THE OCEAN IS NOT THE SAME AS THAT OF GROUND STATIONS.
THE ENVIRONMENT IS VERY COMPLEX AND THERE ARE MANY LINKS IN THE
TECHNICAL CHAIN. IN ADDITION, THE SHIP IS CONSTANTLY ROCKING. FOR
THESE REASONS, FOREIGN MEASURING SHIPS ONLY CARRY OUT MEASURING
ASSIGNMENTS. ONLY CHINA'S MEASURING SHIPS COMBINE MEASURING AND
CONTROL IN ONE SHIP.

    SIMULTANEOUS DEPLOYMENT IN THE ATLANTIC, PACIFIC AND INDIAN 
OCEANS

    THE ULTIMATE GOAL BEHIND THE LAUNCHING OF THE SHENZHOU
EXPERIMENTAL SPACECRAFT IS TO LAUNCH A MANNED SPACECRAFT. A MANNED
SPACECRAFT MUST CONSTANTLY KEEP IN TOUCH WITH CHINA DURING THE
COURSE OF ITS FLIGHT. THIS IS A MATTER OF SOLVING THE ORBITAL AND
COMMUNICATIONS COVERAGE PROBLEM. WHILE THE SPACECRAFT IS REVOLVING
AROUND THE EARTH IN ORBIT, WE MUST ASSURE A COMPARATIVELY HIGH
COVERAGE RATE. UNDER CURRENT CONDITIONS, WE MUST DISPATCH SHIPS TO
THE ATLANTIC, PACIFIC AND INDIAN OCEANS IF WE ARE TO MEET THE NEED
FOR CONSIDERABLE COVERAGE. DURING THE LAUNCH OF THE SHENZHOU
EXPERIMENTAL SPACECRAFT, CHINA DEPLOYED MEASURING SHIPS
SIMULTANEOUSLY IN THE ATLANTIC, PACIFIC AND INDIAN OCEANS FOR THE
FIRST TIME. EVEN THOUGH CHINA ONLY HAS FOUR SHIPS, A COVERAGE RATE
OF NEARLY 75% WAS ASSURED. ALL OF THE CRITICAL TRACKING AND CONTROL
EVENTS FOR THE EXPERIMENTAL SPACECRAFT WERE COMPLETED ON THE SHIPS.
WHILE THEY WERE COMPLETING THESE TASKS, THE MEASURING SHIPS WERE
ALL FAR AWAY FROM THE MOTHERLAND. FOR EXAMPLE, CONTROL OF
SPACECRAFT REENTRY WAS DONE IN THE SOUTH ATLANTIC OCEAN. THE WORK
WAS DIVIDED AMONG THE MEASURING SHIPS SPREAD OUT OVER THE ATLANTIC,
PACIFIC AND INDIAN OCEANS. EACH OF THE SHIPS IMPLEMENTED SPACECRAFT
COVERAGE FOR DIFFERENT ORBITS AND ORBITAL SEGMENTS, THEREBY MEETING
COVERAGE REQUIREMENTS.

    A NEW RECRUIT FOR AEROSPACE TRACKING AND CONTROL

    THE COST OF CONSTRUCTING A MEASURING SHIP IS EXTREMELY HIGH.
HOWEVER, SUCH A SHIP HAS A CONSIDERABLE WORKING LIFE (GENERALLY
15-20 YEARS). IN ORDER TO MEET THE DEMANDS POSED BY AEROSPACE
TRACKING AND CONTROL, BOTH YUANWANG 1 AND YUANWANG 2 HAVE UNDERGONE
TWO COMPARATIVELY LARGE TECHNICAL RECONSTRUCTIONS, AND THEY CAN 
CONTINUE TO OPERATE FOR ABOUT 15 TO 20 MORE YEARS. YUANWANG 3 AND
YUANWANG 4 ARE COMPARATIVELY NEW. HOWEVER, FROM THE STANDPOINT OF
THE DEVELOPMENT OF INTERNATIONAL AEROSPACE TECHNOLOGY AND AEROSPACE
TRACKING AND CONTROL TECHNOLOGY, USING MEASURING SHIPS FOR TRACKING
AND CONTROL OF SPACECRAFT IS BY NO MEANS THE IDEAL METHOD. IN THE
FIRST PLACE, A MAJOR WEAKNESS OF MEASURING SHIPS IS THAT THEY
DELIVER VERY LITTLE BANG FOR THE BUCK AND THE SHIPS CONSUME
CONSIDERABLE AMOUNTS OF RESOURCES. CHINA DOES NOT MAKE VERY MANY
AEROSPACE LAUNCHES, AND THE LOCALITIES IN WHICH MEASURING SHIPS
OPERATE ARE OFTEN FAR FROM CHINA. THEREFORE, WHEN A MEASURING SHIP
PUTS OUT TO SEA, IT SPENDS MUCH TIME IN NAVIGATING. DURING THIS
TIME, IT MUST CONSUME A VERY LARGE AMOUNT OF FUEL OIL, WITH VERY
HIGH CONSUMPTION COSTS. IN THE SECOND PLACE, MAINTENANCE
EXPENDITURES FOR A MEASURING SHIP ARE ALSO COMPARATIVELY LARGE.
OFTEN BUILDING THE SHIP IS AFFORDABLE, BUT KEEPING IT IN GOOD
REPAIR IS NOT. HOWEVER, OUR MEASURING SHIPS ARE MULTI-FUNCTIONAL.
THEY CAN BE FLEXIBLY DEPLOYED IN ACCORDANCE WITH THE DEMANDS POSED
BY VARIOUS ASSIGNMENTS. FOR EXAMPLE, THE SHIPS CAN BE FLEXIBLY
DEPLOYED IN THE ATLANTIC OCEAN, THE PACIFIC OCEAN, THE INDIAN OCEAN 
AND ELSEWHERE IN ACCORDANCE WITH THE DEMANDS POSED BY VARIOUS
LAUNCH ORBITS AND VARIOUS SATELLITES. OCCASIONALLY, THEY CAN ALSO
CARRY OUT ASSIGNMENTS IN THE SOUTH CHINA SEA. FROM THIS STANDPOINT,
MEASURING SHIPS HAVE A COMPARATIVELY HIGH DEGREE OF FLEXIBILITY.
THUS, FROM A LONG-TERM STANDPOINT, IT IS STILL NECESSARY FOR CHINA
TO HAVE A CERTAIN NUMBER OF MEASURING SHIPS. HOWEVER, WE SHOULD NOT
HAVE TOO MANY OF THEM.

    WITH THE DEVELOPMENT OF MODERN SCIENCE AND TECHNOLOGY,
AEROSPACE MEASURING HAS EVOLVED FROM EARTH-BASED MEASURING TO
SPACE-BASED MEASURING. BY THE EARLY 1990'S, THE U.S. HAD ALREADY
LAUNCHED A RELAY SATELLITE. IN RECENT YEARS, RUSSIA HAS ALSO
LAUNCHED A RELAY SATELLITE. AS OF NOW, AEROSPACE TECHNOLOGY IN THE
U.S. AND RUSSIA HAS ALREADY ENTERED THE DEVELOPMENTAL STAGE
CHARACTERIZED BY THE USE OF RELAY SATELLITES FOR MEASURING AND
CONTROL. BOTH THE U.S. AND RUSSIA HAVE DEPLOYED A RELAY SATELLITE
ABOVE THE EASTERN HEMISPHERE AND A RELAY SATELLITE ABOVE THE
WESTERN HEMISPHERE SO AS TO COVER THE ENTIRE EARTH. THUS THE U.S.
AND RUSSIA CAN CARRY OUT ORBITAL AND TELEMETERING MEASUREMENTS ON 
ANY SATELLITE LAUNCHED BY ANY COUNTRY.

    IN ADDITION, USING THE GPS SYSTEM IS ALSO A COMPARATIVELY
POPULAR MEASURING METHOD ON THE INTERNATIONAL STAGE. THIS TYPE OF
MEASURING METHOD ACTUALLY USES THE U.S.'S GLOBAL POSITIONING SYSTEM
SATELLITES TO "KEEP AN EYE ON" THE POSITIONS OF LAUNCH VEHICLES AND
SATELLITES FLYING THROUGH SPACE. A METHOD IS ADOPTED WHEREBY, FOR
EVERY OTHER UNIT OF TIME, A POINT IS MEASURED (INCLUDING
INCLINATION, AZIMUTH AND RANGE). A PRECISE TRAJECTORY IS DERIVED BY
CONNECTING TOGETHER COUNTLESS INDIVIDUAL POINTS. IN THE YEAR THAT
YUANWANG 3 TRIAL FLIGHTS WERE CARRIED OUT, THE MEASURING STATION 
ADOPTED THE GPS MEASURING METHOD, WITH VERY GOOD MEASUREMENT
ACCURACY.

    EVEN THOUGH SCIENCE AND TECHNOLOGY HAVE DEVELOPED AND AEROSPACE
TRACKING AND CONTROL IN THE U.S. AND RUSSIA HAS ENTERED THE STAGE
OF RELAY SATELLITE DEVELOPMENT, NEVERTHELESS IT IS OF COURSE TRUE
THAT SEABORNE MEASURING HAS ITS ADVANTAGES IN CHINA. BY LAUNCHING
TWO RELAY SATELLITES, THE U.S. AND RUSSIA CAN TRACK SEVERAL DOZEN 
OR EVEN MORE TARGETS UNDER ANY AND ALL WEATHER CONDITIONS. HOWEVER,
IT SHOULD BE CONSIDERED THAT THE FREQUENCY OF LAUNCHES IS VERY HIGH
IN BOTH THE U.S. AND RUSSIA. IN BOTH CASES, THERE ARE SEVERAL DOZEN 
OR EVEN MORE THAN A HUNDRED TARGETS FLYING IN SPACE ON ANY GIVEN 
DAY. IT WAS BOTH EFFICIENT AND ADVANTAGEOUS FOR THE U.S. AND RUSSIA
TO DEVELOP RELAY SATELLITES, AND THE U.S. AND RUSSIA ARE ABLE TO
GIVE FULL PLAY TO THEIR POSITIVE ROLE. HOWEVER, DUE TO THE
LIMITATIONS OF CHINA'S NATIONAL STRENGTH, THE FREQUENCY OF LAUNCHES
IS COMPARATIVELY LOW HERE, AND CONSEQUENTLY WE CANNOT GIVE FULL
PLAY TO THE ADVANTAGES ACCRUING FROM THE USE OF RELAY SATELLITES.
MOREOVER, MEASURING SHIPS ARE HIGHLY MOBILE, AND OTHER MEASURING
MEANS ARE NOT TO BE COMPARED IN THIS RESPECT.

    MUCH HAS OCCURRED IN THE PERIOD WHICH BEGAN IN THAT FIRST
SPRING IN THE 1980'S, WHEN A YUANWANG MEASURING SHIP FIRST
DISPLAYED ITS CAPABILITIES IN THE PACIFIC OCEAN, AND WHICH RUNS
RIGHT UP TO TODAY, WHEN MEASURING SHIPS ARE SIMULTANEOUSLY DEPLOYED
IN THE ATLANTIC, PACIFIC AND INDIAN OCEANS: THE EQUATOR HAS BEEN 
CROSSED DOZENS OF TIMES; MANY MAJOR NATIONAL-LEVEL EXPERIMENTS AND
FOREIGN SATELLITE LAUNCH ASSIGNMENTS HAVE BEEN SUCCESSFULLY
COMPLETED; AND FOUR GREAT LEAPS HAVE BEEN MADE--THE LEAP FROM THE
LAND TO THE OCEAN, THE LEAP FROM SURFACE TO UNDERWATER, THE LEAP
FROM DOMESTIC TO INTERNATIONAL, AND THE LEAP FROM MEASURING TO
MEASURING AND CONTROL. CHINA'S OVERALL OCEANGOING AEROSPACE
TRACKING AND CONTROL CAPABILITY HAS STRIDDEN INTO THE FRONT RANKS
ON THE INTERNATIONAL STAGE. WE HAVE CONFIDENCE AND GOOD REASON TO
BELIEVE THAT THE QUALITY OF CHINA'S AEROSPACE TRACKING AND CONTROL
WILL RISE TO A YET HIGHER LEVEL IN THE FUTURE.

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