Chinese space technologists have made "considerable modifications" to previous versions of China's unmanned spacecraft to enable Shenzhou-8 to dock with a target orbiter, a spokeswoman for China's manned space program said here Monday.

The unmanned spacecraft Shenzhou-8 is scheduled to be launched at 5:58 a.m. Tuesday and will dock with China's first space lab module, Tiangong-1, spokeswoman Wu Ping said at a press briefing.

"More than half of the 600 or so sets of equipment have been modified, while newly designed devices account for about 15 percent of the total," Wu said.

The modifications were mainly aimed at arming the spacecraft with automatic and manual rendezvous and docking capacities, and to enhance the vehicle's performance, safety and reliability, the spokeswoman said.

"After the improvements, the spacecraft will be able to connect with the target orbiter Tiangong-1 for 180 days," Wu said.