Continued problems with the $600 million Canadarm 2 Space Station Remote Manipulator System (SSRMS) have delayed two Space Shuttle missions by at least a month and may result in a switch of these missions.
STS 104/Atlantis, carrying the $164 million US airlock module, has been put back to early July, while STS 105/Discovery, a logistics and crew exchange mission, is now scheduled for August. The STS 105 may fly first and STS 104 will be pushed further back.
The seven-joint, twin-arm Canadarm 2 will be needed to install the Q airlock module (which allows access from the space station for EVA spacewalks) to the ISS, a job that cannot be done by the Shuttle's remote manipulator system arm.
An attempt to fix a back-up computer or arm controller unit on the 17m- (56ft) long Canadarm will be made by two ISS crew on 8 June. The arm controller routes commands from inside the US Destiny laboratory module.
The unit has two prime data pathways and a back-up over which the commands travel, but the back-up failed, stopping the movement of some arm joints. The other arm's shoulder has a failed pitch joint.
If the 8 June EVA goes well, Atlantis will be launched, followed by Discovery, which will repair the shoulder joint. If the EVA fails, Discovery will fix the Canadarm, Atlantis, following with the airlock module.
To allow for more EVA training, STS 105 would fly in August, Atlantis in September.
Source: Flight International
