A staff member tries to tie ropes with a captive balloon floating in air at a testing ground in Liu'an, east China's Anhui Province, March 29, 2017. The captive balloon is an air platform carrying various devices, such as warning radar, video surveillance equipment, fog detection devices, communication relay devices and imaging equipment. The balloon is expected to play a role in precaution and detection, environmental surveillance, security and protection monitoring. (Xinhua/Cheng Tingting)
