At least three orbiting satellites have been malfunctioning.
Experts have salvaged them all, aerospace scientists said in
Beijing on Monday.
The experts from the Xi'an Satellite Monitor and Control Center
reported that a satellite had gone out of orbit and somersaulted
repeatedly in October 2006.
"Ground control temporarily lost control over the malfunctioning
vehicle," said Dong Deyi, head of the center.
Scientists carefully studied previous orbiting statistics
collected concerning the uncontrollable satellite. Experts analyzed
computer simulations. They decided to try rescue attempts in
December, an optimum time according to their calculations.
The scientists compiled convoluted orders into a short period of
eight seconds. Then they repeatedly sent those orders into space.
After continuous trials, the almost lost satellite started to
respond and the Xi'an center finally gained control of it.
Shortly after the incident, Dong said, another satellite went
out of orbit and was, again, recovered by the experts based in
Xi'an.
In February 2007, the solar cells on another satellite went on
the blink. Principal investigator Yu Peijun and his team in the
Xi'an center calculated various signals emitted from the unstable
satellite. They worked out contingency plans accordingly. After
adjusting the angles of the solar panel, the Xi'an center regained
control over the satellite.
?
?First manned mission threatened by communication
blackout
The Xi'an Satellite Monitor and Control Center also disclosed for
the first time the danger met by the spacecraft, Shenzhou V, and
China's first astronaut Yang Liwei.
It said Chinese aerospace experts saved the country's first ever
manned space mission four years ago as the spaceship was faced with
fatal impact while flying through the communications blackout area
before landing.
Dong said that Yang lost every means to contact with the ground
command and control headquarters as soon as entering the
aerosphere, which fell in the worst case scenario prepared by the
space mission team.
Every spacecraft would be covered by plasma as running through the
aerosphere, according to experts. The plasma obstructs
communications between the spacecraft and command and control
center on the ground.
China was the third country, next to the former Soviet Union and
the United States, to send people in space.
Although space scientists and technologists garnered experience in
controlling the spacecraft after four unmanned tryouts, the
headquarters designed a full list of contingency plans, including a
possible emergency landing in Australian heartland.
"Even radar could not capture any signal from the returning
module," Dong said.
After the Shenzhou V went out of the blackout area, Dong said, the
echo signals from the spaceship were still volatile which
sufficiently threatened a safe landing of astronaut Yang.
The Xi'an center, which is responsible for every landing of the
Shenzhou spaceships since 1999, ordered implementation of the
optical guiding and tracking system instead of communication-guided
landing control, Dong said.
The aerospace technologists used cinetheodolites on the ground to
measure spacecraft position and record the movement of the Shenzhou
V. Precise positioning of the spacecraft enabled officers to
properly control the slow-down parachute which was vital to a soft
landing in Inner Mongolia.
However, the landing spot was nine kilometers east of the
previously planned location, Dong said, citing that the rescue team
reached astronaut Yang 12 minutes after his successful landing.
Onboard Shenzhou V, Yang spent 21 hours in orbiting the earth for
14 times from October 15 to 16, 2003.
Yang's adventure, however, was not the first time that Shenzhou
spaceships were faced with challenges. Xie Mingbao, one key figure
in managing the manned space mission, once revealed that at least
four accidents occurred in the 11-year research and development
leading to the first manned launch in 2003.
Just before its blast-off in January 1999, the first Shenzhou
spaceship was diagnosed with a problem in its backup aerospace
ecosystem. The headquarters decided to delay the planned
launch.
The launch of the second experimental spacecraft, Shenzhou II, was
neither smooth. Xie said an accidental drop left a small dent on
the Long March rocket which was designated to carry Shenzhou II. It
was after careful safety checkups that the spacecraft was allowed
to go.
Shenzhou III experienced even worse fate. Technicians found no
electricity in one socket of the lower part of the carrying rocket,
which indicated a defect in electro-circuit design. The Long March
rocket was then dismantled and transported back to Beijing for a
complete check.
An unexpected chilly spell almost impeded the space journey of
Shenzhou IV. Xie said the headquarters greatly worried about a
one-week chilly spell, which dropped the temperature to minus 27
degrees Celsius. A low-tech solution helped ensure the planned
launch -- Technicians covered the rocket with 200 quilts.
After his space-faring, Yang Liwei helped train his fellow
astronauts and now becomes deputy head of the Space Medical
Engineering Institute of the People's Liberation Army (PLA).
He was honored for his excellence of service at a gathering early
this month marking the 80th anniversary of the founding of the
PLA.
Yang was followed by Fei Junlong and Nie Haisheng who had toured
the outer space for almost five days in October 2005.
China began its clandestine manned space program in 1992, which was
coded as the 921 Project. Since then, China has spent at least 20
billion yuan (US$2.64 billion) in the project and sent three
astronauts into orbit.
The Xi'an center, established on June 23, 1967, is located in
the mountains of northwest China. It has monitored and controlled
more than 100 satellites as well as the six Shenzhou spaceships.
Official records now show that China has over 19 satellites
orbiting the earth.
(Xinhua News Agency August 13, 2007)