Closer Look: Shenzhou-7’s Close Pass by the International Space Station
by Richard Fisher, Jr.
Published on October 9th, 2008
ARTICLES
On September 27, 2008 during its 31st orbit, China’s Shenzhou-7 space mission achieved two of its main objectives: China’s first manned extra vehicular activity (EVA) or space walk, and the first launch of the 40kg BX-1 microsatellite for the purposes of testing new microsatellite technologies, and observing and operating in cooperation with the Shenzhou. The spacewalk by Chinese astronaut Zhai Zhigang received massive coverage in China and internationally and the microsatellite mission was also covered well by the Chinese media. What the Chinese media did not cover, and even more surprisingly has so far gone unremarked by the United States or Russian governments, was the fact that about 4 hours after launching the BX-1, the Shenzhou-7 flew to a distance of about 45km (27 miles) from the International Space Station (ISS).
The U.S. National Aeronautic and Space Administration (NASA) and the U.S. Strategic Command (USSTRATCOM) devote considerable resources to protect the $35-$100 billion[1] International Space Station from possible collisions with space debris. On rare occasions large object do get close enough to the ISS to warrant avoidance maneuvering. When traveling at Low Earth Orbit speeds of 7.7km per second, or about 17,000 mph, objects smaller than 5mm pose a threat to the ISS and have to be regarded seriously. According to calculations by the U.S. Strategic Command, the Shenzhou-7 reached a point about 45km below and forward-right of the ISS on September 27, 2008. The difference in orbital altitude of the respective spacecraft ensured that there was no danger of collision. But the Shenzhou-7 had just launched its previously untested BX-1 microsatellite and a possible malfunction might have very quickly posed a potential danger to the ISS.
International Space Station: On September 27, 2008, China’s Shenzhou-7 spacecraft flew to a position about 45km below and in front of the US and Russian manned International Space Station.
To date it is not known whether China made any attempt to warn Washington or Moscow that its spacecraft were going to approach the ISS. But even if that happened, it is still necessary to ask questions about China’s potential motivations. The orbit used by Shenzhou-7 was almost the same as used by the previous two manned Shenzhou missions, and an ability to reach the ISS points toward obvious opportunities for cooperation. However, it is not assuring that China’s manned space program is controlled completely by the China’s People’s Liberation Army (PLA), which has made dual civil-military use of all previous six Shenzhou spaceship missions. The PLA may have plans to develop active space combat capabilities and one military "dual use" for the Shenzhou-7/BX-1 mission may have been to validate a "co-orbital" anti-satellite capability. This would contrast with the "direct ascent" ASAT capability demonstrated by China in January 2007. As such, the silence from Washington and Moscow on this matter is troubling.
BX-1 Before Launch: This picture shows the BX-1 microsatellite mounted on top of the orbital module of the Shenzhou-7 spacecraft, before assembly for launch. Source: Chinese Internet
Timeline of Events
Shenzhou-7 was launched on September 25 at 21:10 Beijing Time (13:10 Universal Time/Greenwich Mean Time UTC/GMT), for a mission that would last 68.27 hours. September 27th was a day of national triumph for China as the Chinese leadership and through a wide television audience, Chinese observed in real time the first space walk by a Chinese astronaut. As can best be determined from available data, a timeline for major activities that day of the Shenzhou-7 is as follows:
08:43 UTC/GMT: Spacewalk by Zhai Zhigang starts and last for about 15 to 19.35 minutes.
11:24 UTC/GMT: At a point about 500km from the ISS the Shenzhou-7 launches the BX-1 microsatellite.
15:07 UTC/GMT: At 4.13 hours later, likely in the skies between Australia and New Zealand, Shenzhou reached its closest 45km proximity with the ISS.
Timing for the Shenzhou space walk and the launch of the BX-1 microsatellite has been reported by the official Chinese media.[2] These are usually in Beijing Time and require the subtraction of 8 hours to get UTC/GMT. The source of the initial indication of the Shenzhou pass by the ISS appears to have been generated by a non-government observer, who placed proximity data based on a Collision Avoidance (COLA) program for satellites, on popular Western and Russian space issue web forums. This individual estimated that the Shenzhou-7 would approach to 36.6km from the ISS at 15:07 UTC/GMT.[3] This data was then apparently copied on to a popular Chinese web page where it was first viewed by this analyst.[4] In addition, an amateur space satellite observer noted the opportunity to observe the Shenzhou-7 and ISS in close proximity on September 27 over New Zealand.[5]
Danger of Collision?
According the U.S. Strategic Command (USSTRATCOM), which among many other duties, monitors all objects of interest in outer space, has concluded that despite a close proximity pass between Shenzhou-7 (SZ-7) and the ISS on September 27, there was no danger of a collision between these two spacecraft, provided they maintained their established orbits. The description by USSTRATCOM relayed to the IASC by the NASA Public Affairs Office on October 7, 2008 is as follows:
"The highest apogee [farthest orbital point from the Earth] for SZ-7 vehicle was, per USSTRATCOM 336 km. Lowest perigee [closest orbital point to the Earth] for ISS was 347 km. The total distance between SZ-7 and ISS at the time noted in the Chinese website (
) was 45 km on September 27, 2008 (271/15:07 GMT), 18km below x 41km ahead x 8km starboard at Time of Closest Approach (TCA). SZ-7 speed relative to ISS was 3.1 km/s."[6]
USSTRATCOM also relayed that even if there had been perfect alignment between the Shenzhou-7 and the ISS, the closest possible approach would have been to 11km, provided the Shenzhou-7 did not alter its orbit.[7]
But in addition to the proximity of the larger spacecraft, it is also necessary to consider the proximity of the BX-1 microsatellite as it orbited the Shenzhou-7 craft. According to one Chinese report on October 5, "Since September 30, the control center changed its track six times to draw it closer to the space vehicle step by step, and finally it succeeded in orbiting the capsule [settling] on an elliptical track of 4 kilometers multiplying 8 kilometers."[8] Another report indicated that the BX-1 eventually settled to a distance about 100km behind the Shenzhou.[9] One might conclude then, in the hours after its launch, the BX-1 microsatellite’s distance from the Shenzhou-7 was increasing. Unclear, however, was the orbital inclination or flight angle of the BX-1 around the Shenzhou-7, though pictures of later returned by the BX-1 show that it flew "above" the Shenzhou-7. But one tentative conclusion would be that in the hours before passing the ISS, the BX-1’s orbit around Shenzhou was expanding upward in a direction that would have taken it closer to the ISS, at least offering a greater chance that a potential malfunction might have taken it even closer to the ISS. According to USSTRATCOM, the Shenzhou-7, and presumably the BX-1, were traveling 3.1km/s faster (6,696mph) than the ISS. Would there have been time for the U.S. to react?
BX-1 After Launch: These photos were taken by the BX-1 microsatellite soon after its launch on September 27. One photo clearly shows that the BX-1 was able to reach a position above the Shenzhou-7 spacecraft. Source: Chinese Internet
The U.S. And China Were Watching
USSTRATCOM is responsible for tracking objects in space of security concern to the United States. The U.S. Air Force’s AN/FPS-85 phased array radar located at Eglin Air Force Base in Florida is reportedly capable of tracking 90 percent of man-made space objects, down to "softball" size objects up to 300nm (540km) in outer space. Furthermore, the Air Force controls the distributed AN/FPS-133 radar surveillance "fence" that can track all man-made objects in space, which has been recently upgraded to provide 3-Dimensional tracking plots.[10]
In addition, Australia’s Tidbinbilla Deep Space Tracking Centre, which hosts radar jointly manned by NASA and Australian personnel, would have likely been able to monitor the Shenzhou-7’s passage on its September 27 close pass with the ISS near New Zealand. A third potential source of surveillance would have been the deeper-space U.S. infrared missile early warning satellites, but it is not known whether these would have been monitoring the Southern Hemisphere on September 27. While the U.S.-based radar facilities would have been able to quickly supply data for potential maneuvers for the ISS to avoid the larger Shenzhou-7, it is not known whether the Tidbinbilla radar would have been able to track any potential errant BX-1 events in time to provide proper warning.
Tidbinbilla: This joint-US-Australian Deep Space monitoring facility has supported all U.S. manned space missions, and was likely watching closely as the Shenzhou-7 craft approached the ISS on September 27, 2008. Source: Internet
It is also worth noting that China’s space surveillance system had a clear view of the Shenzhou-7 pass by the ISS. The PLA maintains a fleet of space support ships which are deployed to the Pacific, Indian and Atlantic Oceans to compensate for China’s lack of global land bases for space surveillance. A briefing by Li Ming of the China Academy of Space Technology, given on October 2, 2008 at the International Astronautical Conference, shows that one of China’s space tracking ships was positioned to the North of New Zealand, where it would have had an excellent view of the Shenzhou-7 close pass by the ISS on September 27.[11] China likely deployed a space events ship to this same area to support the 2005 Shenzhou-6 mission.[12]
China Also Watched: An outtake from Li Ming’s October 2, 2008 briefing of the International Astronautical Congress shows the positioning of China’s space events ships, including one North of New Zealand. Source: Li Ming via Rob Coppinger, Flight International
According to USSTRATCOM it is standard practice for the U.S. to monitor intently all objects entering a "conjunction notification box" around the ISS that measures 25x25km, and then 2km deep. Should an object be assessed as having the potential to enter this box that would trigger a reaction by the ISS by NASA controllers. On August 28, 2008 the ISS had to use a boost from the European "Jules Verne" Automated Transport Vehicle (ATV) to avoid a piece of an old Russian radar satellite, which otherwise would have passed to within one mile of the ISS. The previous time the ISS had to perform a similar maneuver was in 2003.[13] On September 29, 2008 the Russian satellite piece was expected to pass to about 30km from the ISS.[14] An orbital adjustment scheduled for October 2, to facilitate a Russian Progress resupply vessel was delayed to October 4 in order to avoid the Soviet satellite fragment.[15]
The U.S. is also concerned about smaller objects, that when traveling at normal space velocities, could cause great damage to the ISS. According to one 2002 study objects less than 5mm in size may pose a threat to the ISS.[16] Loss of atmosphere is not an unknown danger. The failure of a ventilation valve during the initial June 30, 1971 re-entry maneuvers of the Soviet Soyuz-11 spacecraft saw the loss atmosphere in about 115 seconds, leading to the near immediate deaths of three Cosmonauts.[17] Two Russian Cosmonauts, Sergei Volkov, Oleg Kononenko, and one American, Gregory Chamitoff, were aboard the ISS on September 27. Had there been a malfunction of the BX-1 in the circumstances of September 27, it is not clear whether the ISS would have received sufficient warning to undertake avoidance maneuvers, increasing the chance of having to evacuate the ISS.
Potential Reasons for Proximity Pass
Given the dangers of operating in close proximity, why did the Chinese military-space authorities take the risk of putting the Shenzhou-7 on an orbital path that would take it so close to the ISS? On one level, the timing and path of the Shenzhou-7 mission was dictated by its operational requirements. On September 6 the Chinese media announced a launch window between September 25 and 30. The timing of the lift-off on September 25 was selected in order to provide an appropriate "daylight" window for the space-walk on September 27. Fears of poor weather may have also played role in the final timing. The orbital altitude was also similar to the previous two Shenzhou manned missions in 2005 and 2003.[18] Yet it has to be considered that the Chinese leadership was well aware of the predicted ISS path, as well as that of the Shenzhou for any potential launch window, and could have delayed its launch for an appropriate period to greatly increase the closest possible distance between the two spacecraft.
With an assumption of such knowledge, then China’s decision to time the Shenzhou-7 flight path to coincide with the ISS could be regarded as consistent with the dual civil-military nature of all previous Shenzhou missions. The first three unmanned missions in 1999, 2001 and 2002, plus the first two manned missions in 2003 and 2005, all performed either electronic or electro-optical surveillance missions for PLA, in addition to "science" missions, largely to validate spacecraft technology. Shenzhou-7’s key science mission was to validate China’s Russian-inspired EVA suit technology, advance some technologies needed for future space station missions, and launch the dual civil-military BX-1 microsatellite. The PLA, as have Chinese military leaders historically, place great importance on the skillful practice of many forms of deception. It would not be beyond consideration for the PLA to have "hidden" a larger Shenzhou-7 military exercise in plain sight.
And even though China has been largely transparent about much of the content of the Shenzhou-7 mission, one has to consider that whether deliberate or not, the timing of the BX-1 launch just before reaching its closest proximity to the ISS, could also serve to validate a potential "co-orbital" anti-satellite (ASAT) technology. Co-orbital anti-satellite systems, which catch up to the target in orbit, were the preferred ASAT technology option of the former Soviet Union. In the early 1960s the design bureau of Vladimir Chelomei, Anatoly Savin and NPO Lavochkin combined to develop the Istrebitiel Sputnikov (IS), or Interceptor Satellite. The Soviets launched about 40 IS and target satellites between 1963 and 1982 to test and practice this ASAT method.[19] The advantage is that a "co-orbital" ASAT could take advantage of the slower less powerful rockets of the time, but use accuracy and timing to ensure interception. The direct-ascent ASAT tests demonstrated by the PLA from 2005 to 2007 required a much faster missile, which the PLA has in the KT-1/SC-19 vehicle.
Istrebitiel Sputnikov: From 1963 to 1982 the former Soviet Union launched about 40 IS interceptors and target satellites to perfect “co-orbital” ASAT capabilities. Source: NPO Machinostroyenia
Also, in 1964 the Soviet’s Korolev design bureau began working on a military variant of its Soyuz manned spacecraft, which remains the Russian manned space workhorse, and guided the design of the Chinese Shenzhou. At first it was proposed that Cosmonauts leave the Soyuz to inspect or destroy enemy satellites, and when that was judged too risky, it was proposed that the Soyuz launch unguided rocket mines at the enemy satellite. It was also proposed that a modified two-part Soyuz craft provide in-orbit refueling to allow ASAT operations up to orbits of 6,000km. However, in 1966 following the death of Korolev, the Soviet military cancelled plans for combat versions of the Soyuz, moving manned combat platform development to Chelomei’s bureau, and instead concentrated on unmanned ASAT programs.[20] It is likely that China is much aware of the military history of the Soyuz. China’s decision to adopt the Shenzhou’s orbital module for military surveillance missions at least points to the possibility that China may also be considering space-combat modifications for the Shenzhou orbital module.
Surveillance Shenzhou: This collection of pictures of the Shenzhou orbital modules from the first five missions show their ELINT, radar surveillance and electro-optical surveillance payloads. Source: Chinese Internet
While also having the potential for being developed for many non-kinetic communication or surveillance missions, BX-1 microsatellite could also be used as the basis for a satellite interceptor for surveillance or destruction missions. Its relatively low-resolution camera could be replaced with a much higher resolution system with longer range to image and home in on selected targets. A small boost motor might provide enough power for a direct path toward a close target, with course corrections supplied by the liquid-ammonia-powered thrusters as used by the BX-1. It is also possible that the interceptor stage of the SC-19 ASAT vehicle could provide the basis for an interceptor that could be used by a military-Shenzhou or other future Chinese unmanned or manned spacecraft.
Combat Shenzhou Preview ?: This video outtake shows a simulation of the BX-1 launching from the Shenzhou-7 spacecraft. Could this also preview active combat modifications for the Shenzhou orbital module? Source: Li Ming via Rob Coppinger, Flight International
While consistent with its position for at least one previous Shenzhou mission, the location of the PLA space tracking ship near New Zealand was also "convenient" for providing targeting data and monitoring for a potential military exercise. Assuming it was a military exercise, then it possible to consider that the PLA may view the conduct of such ASAT operations in the Southern Hemisphere as preferable due to a lack of U.S. space monitoring in these regions.
China’s leadership may also be attempting to send political-military messages by having used its BX-1 as it did on September 27. A close pass by the ISS, in a manner following China’s direct-ascent ASAT exercises from 2005 to 2007, may be intended to tell Washington that China will not be constrained in its behavior in Outer Space. Also, in attempting to create a "near incident," that came close but did not trigger defensive measures for the ISS, China may also be trying to strengthen the arguments of those in the U.S. foreign policy and space policy establishment who have long advocated for a higher level of space cooperation with China. The prospect of improving flight safety would be an attractive incentive. The ultimate goal for China might be to gain active access to the ISS itself. The next set of Shenzhou missions are slated to test and validate space docking technology and maneuvering. China has apparently purchased significant amounts of space station technology from Russia, including a version of the Russian APAS docking system[21], which China will likely closely copy, and then possibly use to support future missions to the Russian half of the ISS. China would also like to benefit from Western and European manned space technology gained from operations with the ISS.[22] Gaining access to the ISS would also require a level of political acceptance for China that would make possible the weakening or even elimination of U.S. and European Tiananmen-reactive "embargos" and many other restrictions to high technology access.
Cooperation or Confrontation?
If China had been interested in using the Shenzhou-7 mission to advance international cooperation, it could have earned considerable plaudits by notifying Washington and Moscow of its planned proximity pass with the ISS. Even though some might have objected to the dangers of using the untested BX-1 so close to the ISS, there are plenty of U.S. and European officials who would have been flattered by China’s effort to reach out and "build confidence." Yet China apparently chose not to do so. Instead, Chinese officials offered comments that could be interpreted as deceptive.
During a September 22 conversation with reporters, Major General Cui Jijun, commander of the Jiuquan Satellite Launch Center (responsible for launching Shenzhou-7), responded to a question in which unidentified "foreign reports" had suggested that Shenzhou-7’s microsatellite would be an "offensive weapon." Cui, whose command puts him in good position to advance to higher levels of the General Armaments Department, was said to respond with a "loud and hearty laugh." He then was reported as saying "seriously, a small satellite is not a missile," and then he was quoted saying "I believe that in the vastness of space, wide space, that the chance of collision between two small satellites is highly unlikely…there is no need to take the initiative to attack other countries satellites."[23] This report does not record General Cui saying anything about how Shenzhou-7’s microsatellite would actually be launched in a manner that could threaten the manned International Space Station. Cui’s comments serve to recall China’s consistent and vocal opposition to the militarization of space since the early 1980s, with China having undertaken multiple missile and laser-based anti-satellite programs since at least the early 1990s.
Major General Cui Jijun: The commander of the Jiuquan Satellite Launch Center, responsible for the launch of Shenzhou-7, discounted the chance of a satellite “collision” during a September 22 interview. Source: Chinese Internet
Clearly, it would behoove the interests of China as well as the United States if there could be greater cooperation in space that would create the confidence necessary to avoid tragic space accidents or a space-arms race. The United States and Russia were able to reach such an accommodation in the early 1990s because Moscow has abandoned its expansive military-space ambitions, albeit due to the economic crisis caused by the collapse of the Soviet economy. Had there been no Soviet collapse in 1990 the U.S. may have had to contend with Soviet space weapons like the Skif/Polyus laser platform, large and small armed space planes like the Buran and MAKS programs, and even a potential military space station with docked space shuttle bombers based on the Buran space plane.[24]
Weapons and Deception: Seen before its May 15, 1987 failed test flight, the Soviet Skif-DM/Polyus laser weapon space platform is famously seen with the Russian word “MIR” or “Peace,” written on its side. Source: Internet
As long as China’s space program is in the hands of its generals it will largely reflect the PLA’s strategic requirements. This was the case for the former Soviet Union where the military also controlled the Soviet space program. As seen by its development of multiple ASAT systems, its willingness to make military use of manned space programs and its outright deceptions, China is increasingly following the Soviet example of seeking military dominance of outer space. China’s January 2007 ASAT demonstration, following years of gathering Chinese military-academic writing on the need for China to develop space warfare capabilities, combined with its space arms control diplomacy of deception, provided a clear warning that China was not yet interested in building the confidence necessary for cooperation in space. Does China’s September 27 close pass by the ISS with the Shenzhou-7 and an untested microsatellite constitute a second such demonstration?
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[1] Alan Boyle, "Whats the cost of the space station?," MSNBC.com, August 25, 2006,
; A 2005 European estimate held that the ISS would cost up to 100 billion Euros for assembly and ten years of operations, see, European Space Agency Web Page, August 9, 2005,
[2] Timing for Shenzhou-7 events from "67 Hours 27 Minutes: Shenzhou-7 Flying Times, Xinhua, September 28, 2008,
[3] Collision Avoidance (COLA) data posted by "Liss" on the NASAspaceflight.com web forum, September 27, 2008,
and then repeated by "Lss," Novosti I Kosmonavtiki web forum, September 27, 2008,
[4] Posted by "zjjr" Warsky web page, September 27, 2008,
[5] Robert Holdsworth, "ISS and Shenzhou-7 to pass close to each other over NZ,"
, September 27, 2008,
[6] Email to author, October 7, 2008. The IASC thanks the NASA Public Affairs Office for relaying responses from USSTRATCOM to questions regarding the proximity of Shenzhou-7 and the ISS on September 27, 2008.
[7] Ibid.
[8] "Accompanying Satellite Begins Orbiting Shenzhou-7 Spaceship on Sunday," Xinhua, October 5, 2008.
[9] "ShenZhou-7 Human Spaceflight Mission," SinoDefense.com, October 4, 2007,
[10] "20th Space Control Squadron wins first ever Lord Award," Space Observer, Patterson AFB Colorado, October 2, 2008, pg. 14,
[11] Li Ming briefing recorded by Rob Coppinger, "IAC 2008: Video, Shenzhou-7 and future of China’s manned programme," Hyperbola Blog, October 2, 2008,
[12] "Giant Chinese space tracking ship makes rare visit," October 27, 2005,
[13] Tariq Malik, "Space Station Dodges Orbital Junk," August 28, 2008,
[14] "NASA-ISS On Obit Status, September 27, 2008," SpaceRef.com, September 27, 2008,
[15] "ISS orbit correction delayed to avoid collision with space litter," Interfax-AVN, October 2, 2008,
[16] Dr. Ben Greene, "Laser Tracking of Space Debris," 13th International Workshop on Laser Ranging Instrumentation, Washington, D.C., October 10, 2002.
[17] For a recent review of the tragic loss of Cosmonauts Georgiy Dobrovolskiy, Vladislav Volkov and Victor Patsayev, see Grujica S. Ivanovich, Salyut, The First Space Station, Triumph and Tragedy, Chichester: Praxis Publishing, 2008, Chapters 11 and 13.
[18] For analysis of the orbits of Shenzhou 5 and 6 see, Luciano Anselmo, "Orbital Analysis of the Shenzhou-6 Manned Mission In Support of the Malindi Tracking Station," January 27, 2006.
[19] Anatoly Zak, "IS anti-satellite system," Russianspaceweb.com,
[20] For an excellent summary of Soviet military-Soyuz programs see Mark Wade, "Soyuz-R," Encyclopedia Astronautica web page,
[21] Brian Harvey, The Rebirth of the Russian Space Program, 50 Years After Sputnik, New Frontiers, Chichester: Praxis, 2007, pg. 307; numerous official Chinese artists projections of a Chinese space station show a Russian APAS style docking system.
[22] At the 2000 Zhuhai Airshow an official from a European space company explained to the author how China was very interested in Europe’s development of space station technology.
[23] "Jiuquan Commander-in-Chief, Shenzhou 7’s Small Satellite Not Offensive," China.com, September 22, 2008,
[24] This assertion could be arguable in light of Soviet leader Gorbachev’s lack of enthusiasm for such programs, but they were all in stages of late development or early planning by the late 1980s. For a recent review of Soviet era space combat programs see Bill Rose, Secret Projects: Military Space Technology, Hersham: Midland Publishing, 2008, Chapter Five.
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