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STS-104 Mission Overview

Canadarm2 at Work

Mission STS-104 marks the completion of phase two of the assembly of the International Space Station (ISS) as the Space Shuttle visits the ISS for the 10th time.

Phase one preceded with the participation of American astronauts to long-term stay onboard the Russian Mir Space Station. The installation of an Airlock, which will allow astronauts to perform space walks from the Station, brings the ISS to a full independent functionality thus bridging to the final stage - the completion of the assembly of the ISS which is currently targeted for 2006.

The end of phase two also marks the first operational assembly task performed by Canadarm2 as it installs the US-built Airlock weighing 6.5 tons (6,064 kg).

Airlock

The airlock is a pressurized module consisting of two separate chambers. Once installed and activated, the airlock will become the primary path for ISS spacewalks giving the Station the capability to support them without the presence of the space shuttle.

The two cylindrical chambers are divided by a hatch and are identified as the equipment lock and the crew lock. The equipment lock, the larger of the two, is designed as a storage area for spacesuits and will be used by astronauts to suit up, stow all necessary gear and prepare for their excursion outside the station. The crew lock is the portal from which the spacewalkers will exit the Station. The crew lock contains lighting, handrails and internal umbilical assemblies to provide power and communications before spacewalkers activate the internal battery power of their suit.

The airlock is critical for continued construction of the Space Station. It has been specially designed by Boeing to accommodate the size of American and Russian Orlan spacesuits. The massive chamber will serve two key purposes: keep air from escaping when the hatch to space is opened and regulate the air pressure before an astronaut enters or leaves the Station.

Once installed, the airlock will undergo a series of tests by ground controllers and Station crewmembers to verify that its environment, communications and telemetry systems are fully functional prior to its first utilization. Following a successful testing, the airlock will be used for the first time on flight day nine of the mission, as the shuttle crew performs a third spacewalk.

Gas tanks

A total of four gas tanks will de delivered during this mission, two pressurized oxygen tanks and two pressurized nitrogen tanks. The tanks will provide a replenishable source of gas and will also be used to pressurize and depressurize the new Airlock.

Canadarm2 will be operated by Susan Helms on flight day seven and nine as she grapples one-by-one each tank from a pallet in Atlantis' cargo bay and brings them close to the Airlock. Canadarm2 will hand off each tank to spacewalkers who will latch them in place and connect cables and hoses. This manoeuver is performed manually for safety reasons.

Canadarm2

On the fourth day of the mission, Canadarm2 will be operated by ISS crew Susan Helms from the robotic workstation installed inside the Destiny module. Helms will operate the robotic arm and gently lift the airlock from Atlantis' payload bay berthing it onto the Station Unity module.

Canadarm2 will be mostly flown in a manual mode during grapple and unberthing activities, giving the operator greater control over the motion of the Arm, especially as it comes close to Atlantis' cargo bay and the Unity module vicinity.

After unberth, Canadarm2 will perform large motions and be operated in a single joint mode, moving one joint at a time, completing a swing rotation away from both structures.

The installation of the airlock is a critical phase, as Canadarm2 will be operated for the first time following its delivery during Mission STS-100. This maneuver is performed manually for safety reasons.

Canadarm

The Shuttle arm will, as usual, be used quite extensively during this mission. For the second time, both Canadian Robotic Arms will be operated simultaneously.

Astronaut Kavandi will be responsible to operate the Canadarm during the three spacewalks. A foot restraint will be installed on the arm allowing a spacewalker to step into it and be moved around the work area. The Canadarm will be operated from inside Space Shuttle Atlantis.