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.
