The first Chinese astronaut to walk in space is likely to do so around 4:30 pm on Friday, a day after spacecraft Shenzhou VII lifts off.

The historic moment will be broadcast live across the world, the commander-in-chief of the mission's ground operation, Cui Jijun, said yesterday.

Shenzhou VII is scheduled to blast off from Jiuquan in Gansu province tomorrow night. The exact time will be announced today.

The Shenzhou-VII mission entered the countdown stage after the final checks on the spacecraft, the carrier rocket and the ground operation system were completed yesterday morning.

Scientists simulated the ignition of the rocket and the in-flight moves of the capsule to test how the observation, control and communication systems at the Jiuquan Satellite Launch Center would work.

The rocket will be loaded with fuel after an overall quality review and approval from the mission headquarters. And all the settings of the spacecraft and the monitoring systems will be frozen till the launch.

Technicians checked the rocket and the spacecraft on Monday to test how it functioned, Cui said. "All work well."

The space environment will be stable and calm during the mission, said the Center for Space Environment Research and Forecast (CSERF), affiliated to the Chinese Academy of Sciences.

"After analyzing all the conditions, we predict that the space environment will be safe for the launch and the spacewalk," Liu Siqing, CSERF deputy director, said.

Starting yesterday, the center will submit a report on space environment and all operation systems to the headquarters every day untill the completion of mission, Liu said.

The report will cover high-energy electrons, high-energy protons, X-rays and geomagnetic fields, which could affect the spaceship's flight.

Huang Weifen, deputy chief designer of the mission's flight system, said the six astronauts - three to complete the mission and three to be on standby - have reached Jiuquan on Sunday. One of the three on the spaceship will conduct the spacewalk.

The six astronauts have been housed in a guarded quarantine facility, she said.

Other mission staff have to wear masks and sterilized uniforms and undergo health checks before entering the compound, and cannot even shake hands with the astronauts.

Doctors on the compound are closely monitoring the astronauts' physical and psychological states, she said.

All the five satellite-tracking ships are in position to support China's first spacewalk mission. Four of the vessels are in the Pacific Ocean and one in the Atlantic.

Jian Shilong, director of China Maritime Tracking and Control Department, said the ships would track and support Shenzhou VII, and monitor the spacewalk.

The ships, which can control the shuttle's solar panels, its orbit maneuvers and help with its maintenance, are part of China's space telemetry network, which comprises 20 terrestrial surveying stations as well.

A new purpose-built media center will be opened in Beijing tomorrow for overseas journalists covering China's first spacewalk mission. This is the first time the country will open its space mission to foreign media.