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LIDAR tracks Chinese spacecraft landing

14 Oct 2008

A mobile Doppler LIDAR housed in a van has monitored the wind profile and predicted the landing site of China's historic Shenzhou 7 mission.

As China's Shenzhou 7 module parachuted into its landing zone in Inner Mongolia last month, the all important wind profile in the area was being tracked by a mobile Doppler LIDAR system. Having successfully provided data that helped to predict the module's landing site, the team hopes that LIDAR will play a role in future missions.

This recent success comes hot on the heels of the Olympic and Paralympic games, where the team used the same mobile LIDAR system to monitor the wind profile across the sailing lake at Qingdao.

"We did not change the hardware set-up but we did adjust the measurement mode," team member Ben Wu told optics.org. "At the Olympics, our LIDAR gave horizontal wind field information, while this time we provided a vertical distribution. Our LIDAR was about 50 km away from the landing zone."

After the Paralymic games, the team drove its LIDAR system more than 1600 km to Inner Mongolia to a flat and arid grassland plain (known as a steppe) where the Shenzhou module would land.

"It is difficult to get real-time wind profiles using a radiosonde, a kind of balloon to detect quantities such as wind, temperature and humidity in such an autonomous steppe," explained Wu. "A mobile microwave wind profiler is an alternative, but is only available in the boundary layer below 3 km."

Wu and his colleagues started to measure the wind profile near the landing zone two days before the launch of Shenzhou 7. They updated their wind profile every 10 minutes between 08:00 and 17:00, knowing that the capsule would return before sunset.

"The atmosphere in a steppe is very clear," said Wu. "Thanks to this clear air, our LIDAR could obtain the wind profile from the ground up to between 10 and 12 km if there was no cloud."

When the Shenzhou 7 craft returned to Earth on 28 September, Wu and his colleagues along with a team of other meteorological experts were on hand to calculate the landing point and ensure that rescue workers and medical personnel could attend the astronauts as soon as possible.

The Shenzhou 7 mission was China's third manned spacecraft. Astronauts on this mission successfully carried out the country's first spacewalk.

Author
Jacqueline Hewett is editor of Optics & Laser Europe magazine.

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