China Says Work Under Way to Mitigate Space Junk
The Chinese government is implementing a wide series of measures to reduce the amount of debris left in orbit by Chinese rockets and satellites, and to develop a space-surveillance tool to determine what is in orbit, Chinese space-debris experts said.
The measures, some of which already have been put into place, include techniques already adopted by some other space powers to reorbit retired satellites out of the geostationary orbital arc and to render Chinese rocket upper stages passive in orbit by emptying their fuel tanks to prevent the threat of explosion and debris propagation.
The Chinese government has been a member of the 11-member Inter-Agency Space Debris Coordination Committee (IADC) since the mid-1990s. But Chinese officials concede they have been slow in adopting debris-prevention or debris-mitigation measures.
China?s seriousness about space debris has been thrown into question since the January test of a mobile ground-based Chinese missile that was used to intentionally destroy a retired Chinese meteorological satellite, creating thousands of pieces of orbital debris in a heavily used region of low Earth orbit.
The negative global reaction to that event led China to cancel a scheduled April IADC meeting in Bejing. The meeting was switched to July in Toulouse, France. China sent a full delegation to the meeting, which featured at least one blunt exchange between U.S. and Chinese delegates regarding January?s test of the anti-satellite missile.
Li Ming, who headed the Chinese delegation to IADC, declined to outline China?s space-debris policy immediately after the Toulouse meeting. But in response to Space News inquiries, in August he emailed a summary of China?s space-debris policies in reports written by him and by other Chinese space-debris experts.
?China has made a relatively late start in space debris research,? Li said in a preface to the summary of the debris research. ?There is still an obvious gap between China and other advanced countries in space debris-related technologies.?
China?s space-debris research is based at the Purple Mountain Astronomical Observatory, a Chinese Academy of Sciences facility located in Nanjing and home to the Center for Space Debris Observation and Research.
Li said the center and related institutes, working under China?s 11th Five-Year Plan from 2006-2010, are working on four debris-related aspects:
- Space debris surveillance.
- Collision avoidance.
- Satellite debris protection.
- Debris mitigation.
Two optical telescopes, one a 25-inch (65-centimeter) fixed facility and the other a 10-inch (25-centimeter) car-mounted telescope, have been developed as space-surveillance tools and have been used to time the launch of China?s astronaut-carrying capsules to avoid heavier concentrations of debris in low-Earth orbit, Li said.
A Hypervelocity Impact Center created by Harbin Institute of Technology has been created and tasked with developing technologies to shield spacecraft from debris.
Debris mitigation has been the focus of much IADC work to persuade space powers to take measures to reduce the debris-creating potential of their rocket upper stages and their satellites.
Li and Zhang Wenxiang, a research fellow at the Xi?an Satellite Control Center, said Chinese Long March rockets?specifically the Long March (LM) 2C, LM 2D, LM 3, LM 4B and LM 4C vehicles?either already have been fitted with propellant-venting systems or soon will be.
Li said the China Academy of Launch Vehicle Technology has adopted propellant venting for the LM-3A vehicle. Zhang said the propellant-venting design for the cryogenic upper stage of the LM-3 series, which carries heavy satellites into geostationary transfer orbit, has been completed. ?We believe that in the near future we may perform the post-mission passivation? for the upper stage, Zhang said.
Zhang also said recent research has been focusing on ways to better estimate the amount of fuel remaining in satellites so that they can be removed from their operational orbits at the latest possible time, but early enough to be placed into so-called graveyard orbits out of the main orbital traffic lanes.
Zhang said this kind of reorbit maneuver was performed for the first time on a geostationary-orbit Chinese satellite in September 2006, on the FY-2B meteorological satellite.
In a separate presentation, Zhang Ke, senior engineer at the Xi?an Satellite Control Center, said the FY-2B maneuver, which placed the now-retired satellite about 25 miles (40 kilometers) above geostationary position, ?was not enough. ? It indicates that we had developed the re-orbiting technology successfully. In the future, we will improve the estimation process and leave [sufficient] propellant to perform the operation.?
Li said work also has begun on using the remaining fuel in Chinese rocket upper stages to send the stages back into the atmosphere to burn up.
Zhao Changyin, a research fellow at the Purple Mountain Observatory, said China?s space activities as of December 2006 had produced ?more than 300? pieces of orbital debris.
The U.S. Space Command?s Space Surveillance Network, in a catalogue dated July 4, said China-created debris numbered 2,296, behind the 4,281 pieces from Russia and other nations of the former Soviet Union, and 4,189 pieces for which U.S. launches are responsible. Space Command?s public catalogue lists only pieces of debris about four inches (10 centimeters) or larger.
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