SP-4217 Beyond the Ionosphere

 

Chapter 15
 
The Long March to Space: Satellite Communications in China
 
by Zhu Yilin

 

[205] China entered the satellite field in 1965 and has been developing applied satellite systems for economic, scientific, technological, educational, and cultural uses since the launch, on 24 April 1970, of the first Chinese satellite, Dong Fang Hong-1 (DFH-1), named for the Maoist victory song. By the end of 1996, China had launched thirty-seven of its own satellites, including sixteen returnable remote-sensing satellites, seven communications satellites, two meteorological satellites, and twelve scientific and technical experimental satellites, as part of three applied satellite series: low-Earth-orbit returnable remote-sensing satellites, geostationary Earth orbit communications satellites, and Sun-synchronous orbit meteorological satellites (see Table 2). This chapter describes the development of, and the benefits derived from, China's communications satellites.

China entered the field of satellite communications to improve the relatively underdeveloped state of its communications infrastructure. In June 1970, the Chinese Academy of Space Technology proposed a preliminary technical plan for a communications satellite. Not until February 1975, however, did the State Council of China approve the "Report on the Development of Chinese Satellite Communications," which had been outlined by the State Planning Commission and the National Defense Science and Technology Commission. Approval from the State Council of China meant that the task of developing the country's satellite communications was incorporated in state planning.

 

Experimental Communications Satellites

 

China launched its first experimental communications satellite (the so-called Test Satellite-1) on a Long March 3 rocket on 29 January 1984, placing it in a nonsynchronous orbit. Subsequently, the country launched its first geosynchronous experimental communications satellite on 8 April 1984 and parked it in an orbit at 125° E above the equator (see Table 2). The satellite began its trial operation in May 1984 and subsequently has operated normally. It provides China with a variety of services, such as communications in remote districts; the management of water conservation and electric power; telephone, telegram, facsimile, picture, and data transmission; and the broadcast of a standard time and standard frequency. Its actual lifetime in space has greatly exceeded the expected three years.

 

The DFH-2 Operational Satellite

 

China also has placed into geostationary orbit four operational communications satellites parked at 110.5° East (E), 103° E, 87.5° E, and 98° E above the equator, respectively. There are two kinds of these satellites: the DFH-2 (Dong Fang Hong-2), which is basically the same as the experimental satellites, and the four DFH-2A satellites, which are modified versions of the DFH-2.

 


[
206]

Figure 27. An Intelsat IV (F-8) satellite relayed live television pictures of President Nixon's historic 1974 trip to China.

Figure 27. An Intelsat IV (F-8) satellite relayed live television pictures of President Nixon's historic 1974 trip to China. At the time, China sought access to the Intelsat system, but claimed it would not join as long as Taiwan was a member. In 1974, eighty-seven countries were Intelsat members. (Courtesy of NASA)

 

The DFH-2 satellite was launched into geostationary orbit (103? E above the equator) on 1 February 1986. It carried two transponders and a domestic beam antenna. Its uplink and downlink communications frequencies were 6,225 to 6,425 megahertz and 4,000 to 4,200 megahertz, respectively. The antenna beam can cover the whole territory of China, thereby providing effective communications to outlying districts, such as the Xinjiang and Xizang Autonomous Regions, frontier stations, and islands. In April 1986, the DFH-2 satellite took over broadcasting services from the experimental communications satellite, and on 5 February 1987, it began providing fifteen channels for foreign program broadcasting from the Central People's Broadcasting Station. The number of channels available for foreign broadcasting increased to thirty on 30 September 1987. The DFH-2 satellite remained in continuous use until 8 July 1989.

 

[207] Table 2. China's Launched Satellites up to August 1995

 

Launch Date

Satellite Name

Launch Vehicle

Brief Remarks

.

24 April 1970

Dong Fang Hong-1

Long March 1

Broadcast music "Dong Fang Hong"

3 March 1971

Shijian-1

Long March 1

Operated for eight years in orbit

26 July 1975

TTS-1

Fengbao-1

All onboard systems operated normally

26 November 1975

RRSS-1

Long March 2

Operated in orbit three days before landing

16 December 1975

TTS-2

Fengbao-1

All onboard systems operated normally

30 August 1976

TTS-3

Fengbao-1

All onboard systems operated normally

7 December 1976

RRSS-2

Long March 2

Operated three days and then landed

26 January 1978

RRSS-3

Long March 2

Operated three days and then landed

20 September 1981

Shijian-2

Fengbao-1

Three satellites launched by one rocket for the first time

Shijian-2A

Shijian-2B

9 September 1982

RRSS-4

Long March 2

Operated five days and then landed

19 August 1983

RRSS-5

Long March 2

Operated five days and then landed

29 January 1984

Test-Satellite-1

Long March 3

Carried out communications, operational, and technical tests

8 April 1984

ECS

Long March 3

Stationed at 125° E above equator on 16 April

12 September 1984

RRSS-6

Long March 2

Operated five days and then landed

 

[208] Table 2 (continued)

Launch Date

Satellite Name

Launch Vehicle

Brief Remarks

.

21 October 1985

RRSS-7

Long March 2

Operated five days for land survey and then landed

1 February 1986

OCS-1

Long March 3

Stationed at 103? E above equator on 20 February

6 October 1986

RRSS-8

Long March 2

Operated five days for land survey and then landed

5 August 1987

RRSS-9

Long March 2

Operated five days and then landed

9 September 1987

RRSS-10

Long March 2

Operated eight days and then landed

7 March 1988

OCS-2

Long March 3

Stationed at 87.5? E above equator on 23 March

5 August 1988

RRSS-11

Long March 2

Operated eight days and then landed

7 September 1988

Fengyun-1

Long March 4

Achieved predicted goal

22 December 1988

OCS-3

Long March 3

Stationed at 110.5? E above equator on 30 December

4 February 1990

OCS-4

Long March 3

Stationed at 98? E above equator on 14 February

3 September 1990

Fengyun-1

Long March 4

Transmitted cloud pictures to Earth and measured atmospheric density

Daqi-1

Daqi-2

5 October 1990

RRSS-12

Long March 2

Operated eight days and then landed

28 December 1991

OCS-5

Long March 3

Failed to achieve preset orbit because of launch vehicle failure

9 August 1992

RRSS-13

Long March 2D

Operated sixteen days and then landed

6 October 1992

RRSS-14

Long March 2C

Operated seven days and then landed

 

[209] Table 2 (continued)

Launch Date

Satellite Name

Launch Vehicle

Brief Remarks

.

8 October 1993

RRSS-5

Long March 2C

Operated eight days, but failed to land because of malfunction

8 February 1994

Shijian-4

Long March 3A

Operated in a geosynchronous transfer orbit

3 July 1994

RRSS-16

Long March 2D

Operated fifteen days and then landed

30 November 1994

Dong Fang Hong-3

Long March 3A

Placed in quasi-geosynchronous orbit, but failed to station because fuel had drained

TTS--Technical Test Satellite
RRSS--Returnable Remote Sensing Satellite
ECS--Experimental Communication Satellite
OCS--Operational Communication Satellite

 

 

The DFH-2A Satellite Series

 

The first DFH-2A satellite was launched on 7 March 1988 and parked at 87.5? E above the equator. All four C-band transponders aboard the satellite have seen service. Transponders A and B relayed the first and second channels of the Central People's Broadcasting Station. Transponder C was used to transmit programs from Xizang television station and to provide special services for the Bank of China. Transponder D was used to transmit programs from the Yunnan, Guizou, and Xinjiang television stations. The power output of these transponders was 25 percent greater than that of the DFH-2. They were designed to last 4.5 years, or 50 percent longer. Moreover, the DFH-2A can provide 3,000 telephone channels or four television channels in contrast to the 1,000 telephone channels or two television channels provided by the DFH-2 satellite.

On 22 December 1988, China successfully launched the second DFH-2A satellite and parked it in a geostationary orbit at 110.5° E above the equator. Its four transponders relayed educational television programming over thirty channels and provided specialized communications services. On 4 February 1990, the third DFH-2A satellite was successfully launched and parked in an orbit at 98° E above the equator. Subsequently, the fourth DFH-2A satellite was launched on 28 December 1991, but unlike its successful predecessors, it did not achieve the desired orbit because of a firing failure of the launch vehicle's third stage. Nonetheless, the satellite entered an elliptical orbit using an onboard motor.

 


[
210]

Figure 28. Launched in 1988, the first of China's DFH-2A series of satellites relayed television programming to key provincial capitals and provided special services for the Bank of China.

Figure 28. Launched in 1988, the first of China's DFH-2A series of satellites relayed television programming to key provincial capitals and provided special services for the Bank of China. (Courtesy of the Chinese Academy of Space Technology)

 

The DFH-3: The Second-Generation Communications Satellite

 

The second-generation DFH-3 communications satellite was a medium-capacity spacecraft designed to take over from the first generation of satellites and to satisfy an increased demand for domestic communications capacity. It was to be put into orbit by a new launch vehicle, the Long March 3A. The beam of the DFH-3 communications antenna was designed to cover more than 90 percent of the territory of China. The DFH-3 satellite carried twenty-four C-band transponders, of which six were medium powered and were to be used to transmit television programming; the others were low powered for carrying telephone, telegraph, facsimile, and data transmissions. The DFH-3 was capable of relaying six channels of color television programming and 8,100 telephone channels simultaneously. It was designed to last eight years, providing television and radio program and communications services to the entire country by the year 2000.

With the launch of the DFH-3 satellite, Chinese communications satellite technology will reach a new level. The DFH-3 was to be the first communications satellite geared to the needs of the whole society as well as to the needs of business and the state. For the most part, the Chinese Academy of Space Technology carried out the design and manufacture of the satellite in China, although some foreign electronic devices and [211] mechanical parts were purchased, and some components were produced in cooperation with the German firm MBB (Messerschmit-Bolkow-Blohm).

On 30 November 1994, the DFH-3 satellite was launched (about a year later than scheduled) into geosynchronous transfer orbit on a Long March 3A rocket. It was then injected into a quasi-geosynchronous orbit through maneuvers carried out by the onboard propulsion system. These maneuvers showed that the satellite's system design and technical concept were feasible and correct, but unfortunately, the satellite, on the verge of success, could not maintain its orbital position. Leakage in its attitude control thrusters had drained its fuel supply. Consequently, the DFH-3 did not become operative. The results of in-orbit tests indicated that the onboard subsystems, including the transponders, were all normal. The Chinese Academy of Space Technology is currently reviewing its systems and subsystems in the hopes of attempting another launch.

 

Benefits of China's Communications Satellites

 

Communications satellites have brought about many social and economic benefits to China. The application of communications satellites to the development of the country's telecommunications, television, and radio infrastructures has allowed China to leap over the traditional development stage and to realize countrywide coverage in a single step. Prior to the arrival of satellite communications, China's communications and broadcast services, especially its long-distance communications, were backward. Not only was the number of telephone channels small, but the quality of communications was poor. The poor quality and depressed quantity of telecommunications services severely limited the development of the Chinese economy: the speed of information transmission is one of the most important factors affecting economic, cultural, and educational development.

Since 1984, however, to effect a countrywide system of communications satellites, China has established a number of ground satellite stations in several cities, such as Beijing, Kunming (Yunnan Province capital), Urumqi (Xinjiang Autonomous Region capital), Lhasa (Xizang Autonomous Region capital), and Nansha island. Numerous diverse government agencies, such as posts and telecommunications, petroleum, mining, water conservation, electrical power, news, and the military, transmit most of their telephone calls, telegrams, facsimiles, data, tables, and pictures via communications satellites. The result is a significant improvement in communications, especially long-distance communications, and the overcoming of communications difficulties in remote districts. If China were to establish a high-quality radio and television broadcasting network covering up to 80 percent of the country using traditional microwave relay technology, the cost would be about 2 billion yuan ($370 million at the 1993 estimated price and exchange rate). The same services can be provided at a cost of only 1 billion yuan ($185 million at the 1993 estimated price and exchange rate) by a communications satellite system.

By the end of 1995, more than 30,000 receive-only stations had been built. The quality of television program transmissions has been enhanced and geographical coverage expanded. China has established more than 100 communications ground stations so far with antennas larger than five meters in diameter. In the field of educational television, the combined coverage rate achieved by the Central Television Station and local television stations was only 33 percent before 1983. The quality of transmission was low, and its effectiveness was poor because of geographical and climatic conditions. Subsequently, however, communications satellites began carrying two educational stations with a total of thirty hours of daily programming. By the end of 1995, China had more than 1,000 educational television receiving and transmitting stations, more than 10,000 receive-only [212] stations, and more than 62,000 display points in the national educational system, representing a coverage rate of more than 83 percent. According to a poll conducted by the Chinese Educational Television Station, the total population receiving and watching educational television programs has reached 30 million.

As for long-distance telephony and telegraphy, if China were to establish a communications network linking all of its provincial and regional capitals by means of microwave relays and coaxial cable lines, the estimated cost would run into billions of yuan (nearly $1 billion). Use of a satellite communications system lowered this figure to only 500 million yuan ($93 million). By the end of 1995, China had more than 8,000 domestic and 25,000 direct international satellite channels available, as well as ten special satellite communications networks for specifics uses in the development of petroleum, mining, water conservation, and electrical power. At present, China is constructing a number of medium-sized satellite ground stations to add telephone and telegraph satellite channels. The number of very small aperture terminals countrywide has reached 35,000.

Satellite communications also has aided the field of finance. By using satellites for fund transfers, China's banks can reduce greatly the amount of money that is in transit from one point to another and that, as a result, cannot be used. The total amount of funds being transferred among Chinese banks at various levels is, according to one study, as much as 50 billion yuan ($9.3 billion) at any one moment, and the average time required for transfer is six days. By managing the transfer of funds by satellite, this figure can be reduced by as much 50 percent, so that an extra 25 billion yuan ($4.6 billion) would be available for six extra days, thus increasing the amount of working capital and greatly enhancing the availability of funds. The DFH-2A satellites now transmit financial data for the Bank of China. The bank's network is centered at the Beijing head office and includes 350 branch offices. The network not only helps modernize fund clearance and transfer transactions, but also provides financial management information services, telephone communications, business training, and teleconferencing.

For the management of railway traffic, the satellite system of communications and train dispatching has enabled a dramatic increase in the density of train traffic. The time interval between two trains in motion can be reduced from the present eight minutes to three minutes, thereby doubling rail transport capacity without much extra cost. In contrast, the construction of a duplicate railway line from Beijing to Shanghai to double transport capacity would cost 10.2 billion yuan ($1.89 billion), whereas building a satellite communications and dispatching system would cost only 1 billion yuan ($185 million). Preliminary studies to help select a suitable system are currently under way.

 

Future Prospects

 

Although it is a geographically enormous and populous country, China has a limited economic capability. As a result, the country finds it impossible to increase to a large extent its investment in space efforts. Therefore, the selection and planning of its communications satellite program, with an eye to its obvious social and economic benefits, have critical importance. China urgently needs to develop satellite communications and broadcasting capacity to offset its shortage of educational and communications services. Moreover, since the end of 1980s, the demand on communications satellites by both domestic and foreign users has increased rapidly. In particular, the recent appearance of the so-called information superhighway has increased further demand on communications satellites. Undoubtedly, the communications satellite will be one of the main thoroughfares of the future information superhighway.

[213] For these reasons, during the 1990s, China undertook a large-scale development of its communications satellites. Future satellites will operate not only in the C-band, as do existing satellites, but also in the Ku- and L-bands to meet the requirements of educational television, fixed and mobile communications service, specialized data transmission, radio broadcasting, and television transmission. In addition, China plans to develop small, light, inexpensive satellites to meet the requirements of domestic and foreign users of small and medium scale.

At present, some satellites can broadcast directly to homes in several developed countries. The United States, Britain, France, Germany, and Japan have their own direct-television satellites, so that families can receive and watch television programs relayed directly by satellite. It is just a matter of time before China will develop direct-television broadcast satellites. Satellites also have unparalleled advantages over other media for mobile communication. In recent years, a variety of mobile satellite communications systems have been placed in high, medium, and low orbits or are in the planning stage. China, too, needs mobile communications satellites, and it is possible that a mobile communications satellite system will be developed in the not-too-distant future.

To meet the future demand for satellite bandwidth for the national high-speed information network, television broadcasting, and mobile communications, China will need a large number of satellite transponders by the year 2000. Public communications will require sixty to sixty-five transponders, including five to seven in Ku-band, while the special communications needs of various governmental agencies, banks, and large companies will require an additional twenty-five to thirty transponders, including twelve to fifteen in Ku-band. The country's remaining communications will require sixteen transponders, with four in Ku-band. It is anticipated that the number of users of mobile satellite communications will increase to between 200,000 and 300,000. In the field of television broadcasting, the Central Television Station, the television stations of thirty-one provinces, city-states, and autonomous regions, and the estimated four to six educational television channels will require a minimum of forty-four to forty-eight transponders. In total, China will require 145 to 153 transponders at least by the year 2000, including twenty-one to twenty-five Ku-band transponders with fifty-four to seventy-five megahertz of bandwidth each. To meet these requirements, China must build and launch six or seven satellites, if each satellite carries twenty-four transponders, or four to five satellites, if each carries thirty-six transponders.

 

The Next Generation of Communications Satellite

 

To satisfy these increasing communications needs, consolidate domestic markets, and penetrate international markets, China will focus on the development of satellites of higher quality and lower cost. The Chinese Academy of Space Technology, having developed and launched two generations of communications satellites, has begun reviewing its satellite experience and is studying foreign technology and management methods. The first step must be to standardize a common platform bus for a series of satellites. The platform is the base of a satellite. The use of a standard common platform can simplify the work of developing a new platform for each new satellite. A few standard platforms capable of satisfying the needs of various payloads will be developed. The main objectives of this approach are to reduce development time, to improve satellite quality, and to lower costs.

The Chinese space industry is currently developing four series of standard platforms, one of which is a geostationary orbit satellite platform to be used in communications satellites. The DJS-1 platform used by the DFH-3 communications satellite can support a [214] payload weight of 150 to 170 kilograms, while its solar array is capable of generating 1,600 to 2,200 watts of electrical power to supply a payload electric power requirement of 900 to 1,000 watts. The DJS-1 platform also had 1,270 kilograms of available propellant for orbital maneuvers and an expected lifetime of eight to ten years.

The DJS-1 platform will be used to build additional medium-capacity communications satellites and to provide dual-band (Ku- and C-band) communications, mobile communications, data transmission, and other services. To satisfy the demand for large-capacity satellites, China plans to develop a third generation of communications satellite, one with large capacity and a large platform bus, dubbed DJS-2. The main capabilities of one option tentatively planned for the DJS-2 include such features as the ability to support a payload weight of between 400 and 500 kilograms, a solar array output of 4,500 to 6,000 watts, electric power available for payloads of 3,000 to 4,700 watts, 2,200 kilograms of propellant available for orbital maneuvering, and an operational lifetime of fifteen years. The DJS-2 common platform will be able to carry twelve Ku-band transponders of 100-watt output and twenty-four C-band transponders of sixteen-watt output, or fourteen to sixteen Ku-band transponders of 120-watt of output. It will serve to build large-capacity Ku and C dual-band communications satellites, Ku-band direct-broadcast satellites, and tracking and data relay satellites.

As payloads are the core of a satellite and the decisive factor in determining its uses and performances, and as the technical level of Chinese payloads is much lower than that of advanced countries, China must develop or acquire critical payload technologies on a priority basis. The main payloads of a communications satellite are transponders and antennas. In the field of transponders, China must first develop Ku-, L-, S-, and X-band transponders, dual-band (C- and Ku-band) transponders, higher powered transponders, and onboard processing techniques. In the field of antennas, China first must develop multibeam antennas, controllable spot-beam antennas, changeable-shaped-beam antennas, and a number of other antennas, as well as the techniques of onboard switching and intersatellite linkage.

While the Chinese Academy of Space Technology will carry out much of this developmental work, international collaboration must be an important part of those efforts. China should enlarge its range of cooperation with other countries and seek to collaborate at several levels in multiple fields. These efforts should include the importation of certain critical technologies that are of great importance, but such efforts require additional funding to develop and are difficult to achieve in the short term. China also should contract with foreign countries for some subsystems, while the design and integration of the satellite system will remain the responsibility of the Chinese Academy of Space Technology. Finally, China should carry out general programs of international cooperation for the joint development of new satellites, such as that undertaken with Brazil for the development of the China-Brazil Earth Resources Satellite Ziyuan-1 or the Sino satellite being developed jointly with French and German companies.


previousindexnext