Web Exclusive: Chinese Communications Satellites

By | February 10, 2001 | Via Satellite

by Phillip Clark

The communications satellite program of the People’s Republic of China (China) has frequently posed quite a challenge to Western observers seeking to get an overall picture of the global satellite community. Inconsistent nomenclature and difficulty getting definitive information concerning orders and retirements for satellites has muddied the waters considerably. In this article Via Satellite sheds some light upon both the history and the current status of the Chinese satellite program.

The Early Years

There is some evidence that China’s first satellite, Dong Fang Hong (DFH, “The East Is Red”) might have had a limited repeater communications role rather like the first two Telstar satellites, although the Chinese have never commented on this. The Swedish writer Sven Grahn noted that the models and photographs of the satellite carried sets of slot- dipole antennae of two different dimensions around the satellite’s “equator,” indicating that the satellite was being used for unannounced UHF work and thus being capable of performing a role like the early Telstars.

The Chinese-built communications satellites that were subsequently launched used buses with the same Dong Fang Hong name, suggesting that it is a generic term for China’s own communications satellites.

A problem when trying to work out who is doing what within the Chinese space program is that organizations often appear under different names in different publications. The major player is the Ministry of Posts and Telecommunications, which is affiliated with the China Telecommunications Broadcast Satellite Co. Ltd. (Chinasat). These organizations are responsible for the various generations of DFH satellites that have been flown. The primary provider of the Chinese-built satellites is the Chinese Academy of Space Technology.

It should also be mentioned at this point that several other organizations have also procured satellites for China. In 1995 the China Orient Telecomm Satellite Co. Ltd. signed a contract for the provision of a Chinastar satellite using the Lockheed Martin A2100 satellite bus. The Chinastar 1 satellite is now operating in the 87.5 degrees E location. It carries transponders in the standard C-band (3.7-4.2 GHz on the downlink) and in the 14/12 GHz Ku-band. Sinosat Communications Co. has signed an agreement to purchase two Alcatel Spacebus 3000 satellites, one of which has been launched.Sinosat 1 is now operating in the 100.5 degrees E location. It carries transponders in the standard C-band and the 14/12 GHz Ku-band.

DFH-2 Satellites To Geo

The “bus” used for the first Chinese communications satellites launched to geosynchronous orbit was designated DFH-2 and three of these satellites were launched.

The first Chinese attempt to launch a payload to geosynchronous orbit came in January 1984, but the Shiyan Weixing (“experimental satellite”) was stranded in a low orbit due to a failure of the new LOX/hydrogen stage on the CZ-3 (Chang Zheng, “Long March”) launch vehicle. The satellite was able to maneuver to a higher orbit, reaching out to 6,600 km where it was possible to complete some tests of the satellite’s communications payload.

The Chinese were able to solve the Long March third stage problems and within three months they had launched Shiyan Tongbu Tongxin Weixing (“experimental geostationary communications satellite,” shown as “STTW” in Table 1) and positioned it at 125 degreesE. Although it was not as sophisticated as its Western counterparts, STTW was “all-Chinese” and operated for longer than its planned lifetime of three years. The satellite ceased operations when it was boosted off-station at the end of June 1988.

The third and final launch of a DFH-2 satellite came in February 1986 when Shiyong Tongbu Tongxin Weixing (“operational geostationary communications satellite,” shown as STTW 1 in Table 1) was successfully placed into a geosynchronous orbit over 103 degreesE. The location of the satellite was initially somewhat surprising because the Chinese had registered locations designated STW-1 and STW-2 (Shiyan Tongxin Weixing, “experimental communications satellite”) for 70 degreesE and 125 degreesE respectively. STTW was operating over the STW-2 location and the Chinese had re-registered STW-1 for 103 degreesE.

STTW 2 continued to operate with its orbital inclination being regularly corrected until December 1988, but station-keeping maneuvers continued until July 1990. Since the satellite’s design lifetime was three years, it seems likely that operations continued until the satellite drifted off-station.

Improved DFH-2A Satellites

A series of four Chinasat locations was registered with the ITU for further satellites, and these were intended for improved DFH-2A. Starting in March 1988 there were four DFH- 2A satellites launched, with the first three being successfully deployed in geosynchronous orbit.

The third stage of the CZ-3 launcher malfunctioned on the fourth flight, shutting down early during its second burn intended to place the satellite in its transfer orbit. The satellite was separated in a 218-2,450 km orbit inclined at 31.06o. Rather than abandon the satellite, in January 1992 its apogee kick motor was fired to raise the apogee to 35,087 km, and then some time between June 25 and August 24, 1992, perigee was raised from 257 km to 2,003 km. Since the orbital inclination was not close to the “magic” 63.4o, perigee rotated around the orbital plane and thus the satellite could only be used intermittently for communications purposes. (Orbital mechanics analysis shows that if the orbital inclination is chosen so that

sin2(inclination) = 0.8

then the perigee point does not rotate around the orbital plane: the resulting inclination is 63.4349 degrees.)It seems likely that the satellite was to be deployed at the Chinasat-4 location over 130 degreesE, since the three earlier DFH-2A satellites had been located over the Chinasat -1 to -3 locations in numerical order.

Meanwhile, the three other DFH-2A satellites continued to operate successfully. As with the two DFH-2 satellites in GEO, it is not widely known when the satellites ended their communications work. It is possible that the inclination control of the satellites ceased when they ended their communications role (suggesting operating times of five years, compared with the four targeted years), but it will be seen from Table 1 that the three satellites were maintained on-station for far longer than this. It is known that they all carried supplementary science experiments, so possibly these continued after the communications role ended.

Filling The Communications Gap

After the overall successes in operating the DFH-2 and DFH-2A satellites, the Chinese planned to introduce a new-generation, more capable DFH-3 satellite bus, but development problems delayed the maiden flight until November. In the meantime, the elderly Spacenet 1 satellite (launched in 1984) operating over 240 degreesE was purchased by the Chinese in December 1992 and the following June was relocated to 115.5 degreesE (registered as DFH-3-0D with the ITU) where it was operated as Zhong Xing 5 (“star of China”: note that Zhong Xing 1-4 have never been identified by the Chinese, but they might have been the four DFH-2A satellites).

After a flawless launch aboard the second CZ-3A vehicle, the first DFH-3 satellite developed problems. It was deployed in geosynchronous transfer orbit but navigation problems initially prevented the maneuver to GEO. A month after launch the satellite had reached a geosynchronous drift orbit, but the control system problems had resulted in the depletion of virtually all of the satellite’s onboard propellant and the satellite had to be abandoned. The satellite was originally named “Zhong Xing 6,” but this name was later re-used by the second DFH-3A class satellite.

Since the DFH-2A satellites were coming to the ends of their design lives, the Chinese needed further stop-gap measures for their communications satellites. A Hughes HS-276 satellite was purchased and launched as Zhong Xing 7 aboard a CZ-3 in August 1996: this satellite was planned to replace Zhong Xing 5 over 115.5 degreesE. Chinese problems continued when the vehicle’s third stage malfunctioned, leaving the satellite in a 27.250, 200-17,229 km orbit. The orbit was raised to 26.3o, 21,667-46,507 km during the fall of 1996, allowing some limited use to be made of the satellite.

The Chinese have continued to build both their own communications satellites and purchase foreign satellites. Their next commercial satellite launch was the first DFH-3A satellite in May 1997: taking the name Zhong Xing 6 (but shown as “6B” in Table 3), the satellite was successfully deployed at 125 degreesE, the location planned for the first DFH-3 in 1994. In 1998 there were two foreign-built satellites launched. Zhong Wei 1 (“China Star”) launched in May for the China Orient Telecomm Satellite Co. Ltd. It is a Lockheed Martin A2100 located at 87.5 degreesE, the position from which STTW 2 had finally drifted the previous September. Sinosat 1, launched in July for Sinosat Communications Co., is an Alcatel Spacebus 3000 that is operating at 110.5 degreesE. The decade-old STTW 3 was also at this location until drifting off-station in September 1999.

In the meantime, Zhong Xing 5 was finally maneuvered off-station over 115.5 degreesE in December 1999 and entered a retirement orbit.

The most recent Chinese commercial satellite to be launched is Zhong Xing 22, previously announced under the name Feng Huo 1: the satellite is located at 98 degreesE (vacated by STTW 4 in July 1998: originally registered as Chinasat-3 but also bearing the registration Chinasat-22. The frequencies registered for the Chinasat-21 to -25 locations are to be used by satellites providing a mobile communications role.

Companies In Hong Kong

Two telecommunications satellite companies are based in the former British colony of Hong Kong: Asia Satellite Telecommunications Co. Ltd.(AsiaSat) and Asia-Pacific Telecommunications Satellite Co. Ltd.(APStar).

The satellites were originally registered to the United Kingdom as the “colonial power”, but on July 1, 1997 Hong Kong was transferred to Chinese rule. On March 28, 1998 the United Kingdom advised the United Nations (through which satellite ownership is registered) that “With effect from July 1, 1997, the space objects ….. ceased to be carried on the Register of Space Objects of the United Kingdom” and therefore they became classified as Chinese satellites.

AsiaSat was Asia’s first privately-owned regional operator, and the launch of AsiaSat 1 in April 1990 was the first commercial satellite launch performed by the Chinese. AsiaSat 1 was a “second-hand” satellite, originally having been launched in February 1984 as Westar 6 aboard shuttle mission 41B: on that flight the PAM-D perigee kick motor failed to operate, and the satellite (along with Palapa B2) was retrieved by shuttle mission 51A nine months later and returned to Earth for refurbishment and re-sale.

AsiaSat 2, launched in November 1995, was the first flight of the CZ-2E launch vehicle with its EPKM solid-propellant third stage added. In order to fill a gap in its communications requirements, AsiaSat leased the Russian Gorizont 30, which had originally been leased to Rimsat. During October 1997 the satellite was relocated to 122 degreesE, where it operated for nearly two years as “AsiaSat G.” The satellite was relocated to 142.5 degreesE when AsiaSat’s agreement to use the satellite terminated.

At the end of 1997 AsiaSat 3 was launched aboard a Russian four-stage Proton K vehicle on a commercial basis, but the Blok DM3 fourth stage failed when it should have performed the burn to place the satellite into its planned separation orbit, and therefore the satellite was left in a useless geosynchronous transfer orbit inclined at 51o. The insurance coverage paid for a replacement launch, and the identical AsiaSat 3S was launched in March 1999 aboard another four-stage Proton-K. This time the launch was successful and after some initial testing over 98 degreesE, the satellite was relocated to its operational longitude of 105.5 degreesE.

As a back-up in case the launch of AsiaSat 3S also failed, AsiaSat had ordered another satellite designated AsiaSat 3SB: with the successful launch taking place, the 3SB satellite is now planned for launch as AsiaSat 4 aboard an Atlas 3 during the first half of 2002.

The successful launch of AsiaSat 3S saw some “musical chairs” in orbit. During June 1999, AsiaSat G was returned to the Russians and maneuvered off-station over 122 degreesE, and the same month AsiaSat 1 was maneuvered off-station over 105.5 degreesE (where 3S had just arrived) and in August arrived over 122 degreesE to take over from AsiaSat G. When AsiaSat 4 is launched it will be flown to this location, replacing AsiaSat 1.

Although based in Hong Kong before it returned to Chinese rule, APStar was 75 percent owned by companies backed by the Chinese government. After a successful launch, APStar 1 was located over 138 degreesE for initial in-orbit testing and during August-September 1994 it was transferred to 131 degreesE, where it was planned to be operational. Complaints from Rimsat and Japan concerning the interference of APStar’s signals with those from their own satellites meant that the satellite almost immediately had to be relocated back to 138 degreesE, where it is still operational.

The loss of APStar 2 aboard a CZ-2E with a United States Star-63F perigee kick motor, coming after a somewhat similar loss in December 1992 involving Optus B2, did great damage to the Chinese commercial launch program, especially since there was so much “finger pointing” with no one accepting responsibility for the failure. In the cases of both Optus B2 and APStar 2, it is clear from launch footage that the satellite exploded under the payload shroud at almost identical times after launch, but what precipitated the explosions has never been satisfactorily explained in the public domain. Wind shear and the failure of the payload shrouds have been put forward as explanations, but the Chinese have always insisted that their launch vehicles were not to blame for these two losses.

After the APStar 2 loss, APStar 1A was purchased as an interim measure and successfully launched in July 1996: the true replacement for APStar 2, 2R, was launched in October 1997 and is operating over the location planned for the original satellite. In 1999 APStar 2R became a member of the Loral Global Alliance’s Fixed Satellite Service, and it is now being used (without being relocated) as Telstar 10.

In September 1999 APStar announced plans to acquire and launch APStars 3, 4 and 5. The first two satellites are planned as direct broadcasting satellites, while the latter is to be a high power communications satellite, to replace APStar 1, which is expected to be reaching the end of its operational life around 2004.

The Future For China

Table 5 shows a listing of the geosynchronous locations that have been registered via the International Telecommunication Union for satellites operated by the Chinese (including the “transferred” APStar and AsiaSat payloads). Which satellites are actually launched will depend not just on the Chinese finances, but political relations with the United States.

It should be noted that these registrations do not appear to relate to only communications satellites. On October 30, 2000 China launched Bei Dou 1, the country’s first navitation satellite: this satellite was located over 140 degreesE, registered as Chinasat-32, suggesting that the Chinasat-31 and -33 locations will also be used for navigation satellites.

The Chinese have purchased a satellite from Space Systems/Loral that they planned to launch as Zhong Xing 8 aboard a CZ-3B before the end of 1998. This launch was delayed as the United States reviewed its policy concerning the export of high technology to China in the wake of espionage scandals. Although the ban in exporting the satellite still stands in November 2000, the satellite has been built and it is simply awaiting authorization to come through for the export to China.

In April 1999 China Orient announced that it planned to purchase two more satellites, but the schedule would depend upon the economic recovery in Southeast Asia.

Another casualty of the United States export ban was the planned Asia-Pacific Mobile Telecommunications satellite (APMT). This program called for the purchase of two Hughes HS 601HP satellites, one for launch aboard a CZ-3B in 2000 and the other as a spare: the satellite was to be located between 95 degreesE and 125 degreesE. As a result of the export ban in place, in April 1999 APMT terminated the contract with Hughes.

For their domestic program, the Chinese have announced plans for a series of Chinasat-2 satellites to be launched aboard CZ-3 vehicles for the Bank of China. The program has not been mentioned recently, and therefore its current status and launch schedule is uncertain.

A Global Mobile Satellite Information System has been announced for communications via handheld sets using 18-24 satellites in medium altitude (not otherwise specified) orbits: clusters of three to four satellites could be launched aboard the CZ-3A. Once more, the current status and launch schedule is not known.

A pair of data-relay satellites has also been proposed. In July 1999 it was reported that the Southwest Institute of Electronic Technology of China was studying a TDRSS-type system that could provide 85 percent global coverage and support five to 10 satellites at a time. Such a satellite system would be a major bonus when China’s piloted space program begins serious operations – especially when a small orbital station is being occupied by visiting crews.

With the problems of obtaining either components or complete satellites from the United States, the Chinese have both turned inwards for developing new communications satellites or to Europe for purchasing complete satellites. Even if the current United States embargo is lifted, the Chinese will be wary of signing further contracts with U.S. companies in case political whims see the sudden return of such embargoes.

In the meantime, as of October 2000, the Chinese have replaced all of their DFH-2A class satellites with newer DFH-3/3A or foreign-built satellites, and therefore their communications satellite capability currently is the healthiest that it has ever been.

Phillip Clark is a freelance writer, consultant and broadcaster, working as the Molniya Space Consultancy based in Hastings, England. He has specialized in the studies of the former-Soviet and Chinese space programs for thirty years. He has published the monthly “Worldwide Satellite Launches” since the beginning of 1993.

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