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STS-115 Mission Overview

Boosting the Space Station's Power: Canadian Astronaut Flexes Canadarm2 and Walks in Space

It's back to work building the International Space Station (ISS) with the upcoming flight of the Space Shuttle, and once again Canadian talent and technology are front and centre. Slated for liftoff on August 27, 2006, Atlantis and her crew of six, including veteran Canadian astronaut Steve MacLean, will continue constructing the world's largest and most complex space project.

As NASA's third Shuttle mission after its two return-to-flight demonstrations, STS-115 will deliver new truss segments and solar arrays
to the ISS. Installing these new components will have MacLean performing some of the most challenging tasks ever done by any Canadian astronaut. Over the course of the mission, he will be choreographing a series of complex robotic manoeuvres using Canadarm2 to perform assembly tasks—a first for a Canadian
astronaut—and a 6.5-hour spacewalk to install
the power generating panels.

The 12-day mission will be the 19th Shuttle trip to the orbiting laboratory and the 27th flight for Atlantis. Joining Steve MacLean on STS-115 will be commander Brent Jett (veteran of three Shuttle missions and five spacewalks), pilot Chris Ferguson, and mission specialists Joseph Tanner (veteran of three Shuttle missions and five spacewalks), Dan Burbank (veteran of one Shuttle mission to the ISS), and Heidemarie Stefanyshyn-Piper. MacLean, too, is a Shuttle mission veteran, as a payload specialist in 1992 on STS-52.

Safety inspection, Canadian style

After the Shuttle thunders out of the atmosphere and reaches orbit, day two will see the beginning of the examination of every inch of the spacecraft for possible signs of damage from the launch using a unique remote-sensing system: a Canadian-made 15-metre extension to the Space Shuttle's Canadarm.

The Orbiter Boom Sensor System is an extension of the Space Shuttle's Canadarm. (Photo: NASA)

Like a dentist's mirror, the Orbiter Boom Sensor System (OBSS) gives the astronauts the extra reach needed to survey the hard-to-see areas of the Shuttle while in space, including its thermal tiled underbelly, as well as the leading edges of the wings. The boom extension builds on the experience Brampton, Ontario's MDA has gained in developing several generations of space-borne robotic manipulators, such as the Shuttle's Canadarm, the Space Station's Canadarm2, and the upcoming two-armed robot known as Dextre, also destined for the ISS in late 2007 or early 2008.

The end of the boom is outfitted with high-tech digital cameras and laser ranging sensors that can inspect every single Shuttle tile for cracks and holes while in orbit. Designed by Ottawa-based space vision technology developer NEPTEC, one of these Laser Camera Systems consists of a wide-angle, high-speed, high-precision instrument that uses a state-of-the-art scanning technique to generate three-dimensional images. The crew will use the same system to give the Shuttle a second inspection later on in the mission, on flight day nine while still docked to the station, to look for possible micrometeorite damage.

View of the Space Shuttle's nose when docking with the International Space Station 
on Mission STS-114 in 2005. (Photo: NASA)

Coming into port

In the final hour before rendezvous with the station on day three, MacLean will briefly take the Shuttle pilot's seat to support the docking procedures with the ISS. Once moored to the station and settled onboard, preparations begin for the next historic chapter in the assembly of the ISS. Over the next eight days, Atlantis astronauts will conduct a series of intricate robotic manoeuvres using the two Canadarms and perform three spacewalks to set up a new truss system, or structure, on which the second of four pairs of solar arrays will unfurl. Once completed, the solar arrays will form the largest power system ever constructed in space, generating 128 kilowatts.

Cosmic handshake

For Canadians, the action-packed assembly phase of the mission begins soon after docking when MacLean and Burbank prepare for a hand-off manoeuvre involving two generations of Canadian robotic arms. Late on day three, using the Shuttle arm, Burbank delicately plucks the truss assembly out of the Shuttle's cargo bay and hands it off to Canadarm2 operated by MacLean inside the station. This will be the first time in history that Canadarm2 will be assisting in ISS construction under the control of a Canadian astronaut. After this intricate two-hour operation, MacLean will park the robotic arm and its massive payload above the Shuttle cargo bay overnight in preparation for next day's busy construction activities.

On the morning of flight day four, using the Canadian-built robotic workstation located inside the station's U.S Laboratory module Destiny, MacLean begins the first part of the multi-day installation sequence to attach the new truss assembly to the port side of the space station. Gingerly controlling Canadarm2, MacLean moves the P3/P4 truss, which weighed 15.9-tonnes at launch, toward the station and positions it so that claw-like capture latches secure to the orbiting outpost's existing P1truss system. Once the truss is firmly attached, MacLean will command Canadarm2 to release its grip.

MacLean will use the Canadian-developed Space Vision System in these operations. It provides critical images to the robotic workstation. Cameras at the end of the Shuttle arm will send images of the installation taken at various angles to an onboard screen, producing a three-dimensional view. MacLean will thus have a sense of the exact location, movement, and orientation of the payload Canadarm2 is grappling. This information is critical to accurate alignment of the truss for its installation on the station.

The Space Vision System (Photo: CSA)

Follow the Sun

On day four, as MacLean positions Canadarm2 to grapple the newly delivered P3/P4 truss segment at the installation site, Tanner and Stefanyshyn-Piper will step outside and conduct the first seven-hour spacewalk of the mission, plugging in connectors so the truss segments can be powered up by ground controllers once installations are completed a few days later. The spacewalkers will also release restraints that protected the solar arrays during launch and will prepare the Solar Alpha Rotary Joint, or SARJ, and remove its locks for initial rotation of the solar arrays. With this special joint, the panels will be able to rotate and follow the Sun, for the first time. This maximizes the power generating capability of the station.

Canadian spacewalk

On day five, MacLean will don his spacesuit and step out into the vacuum of space for the first time with fellow crewmate Burbank. Their job is to remove thermal covers, install braces and struts, and remove the numerous locks and restraints that immobilized the SARJ during the launch. The spacewalk is expected to last up to seven hours, and the astronauts will be working in close contact with ground controllers who are powering down systems as connections are being made. During the overnight hours, while the astronauts sleep, ground controllers will then power-up and test the SARJ setting the stage for the activation of the solar panels.

Excitement and tension both in space and on the ground reaches its peak on flight day six, when all eyes are focused on the solar panels as they unfurl. For launch, the two 34-by-12-metre panels are folded, origami-style, and loaded into Atlantis' cargo bay. As they slowly open out to their full length, MacLean is supporting the deployment by positioning Canadarm2 next to the newly installed truss system, using its cameras for a close-up view. Meanwhile, Ferguson will be in Atlantis using the Shuttle arm video system to offer secondary camera angles during the four-hour-long operation. If all goes as planned, ground controllers will turn on the solar arrays overnight. MacLean will then walk Canadarm2 off its Mobile Base System to Destiny, the American Laboratory module, prepping it for future arm operations.

Canadarm2 (Photo: NASA)

Overseeing all the delicate operations using the robotic arms are the Canadian flight controllers who will make sure things go smoothly and by the book. Based at the Johnson Space Centre in Houston and Canadian Space Agency headquarters in Longueuil, Quebec, the Canadian engineers work jointly with their American counterparts. Like a ballet sequence, the complex robotic arm manoeuvres during the assembly phase of the mission are choreographed years in advance by the robotics flight control team.

Day seven will see the third and final EVA of the mission when Tanner and Stefanyshyn-Piper go outside the station and prepare the orbiting facility for the next assembly mission, STS-116, currently scheduled for December 2006. They will install a new transponder antenna and clear away a section of the railway track on the new truss, so it can be used by the Canadian-built Mobile Base System. This railcar construction platform transports Canadarm2 and other equipment across the length of the ISS truss.

Close-up view of a portion of the thermal protection tiles on Space Shuttle Discovery's during STS-114 in 2005 (Photo: NASA)

MacLean is to round out his mission by participating in an innovative Earth-observation project that can only be done from a unique platform in space like the ISS. From this 400-km-high vantage point, MacLean will snap hundreds of digital images of Canadian geological features during the mission. By matching his snapshots with satellite data, scientists hope to shed some light on the impact of deforestation and global warming on environmental conditions in the country.

After the remaining maintenance work and all the preparations for the next assembly mission are complete, the crew will undock on day nine and begin preparing the Shuttle for their return flight home three days later.

On day ten, MacLean will be controlling Canadarm to pluck the boom extension out of Atlantis' cargo bay. The crew will then conduct a final visual check-up for any possible on-orbit thermal tile damage to the vehicle, and beam images back to ground control for inspection.

A Canadian space milestone

Circling over 400 km above our planet, the ISS is the most ambitious engineering project ever undertaken and represents an unprecedented international effort between the partner nations.

Right from the start, Canada has had a leading role in this great endeavour. MacLean and his crewmates are building on the extensive heritage of Canadian know-how and innovation already contributed, and STS-115 is a milestone for Canada's space program in that it showcases the most Canadian involvement in ISS assembly to date. Canada's first spacewalker, Chris Hadfield, helped attach the newly completed Canadarm2 onto the station in 2001, while the first set of
solar panels were delivered by Canadian veteran astronaut Marc Garneau in his third flight to space in 2000.

Chris Hadfield is the first Canadian to have walked in space (Photo: NASA)

This is the first mission dedicated to ISS assembly since the Columbia disaster in 2003, which temporarily grounded the remaining orbiters and suspended construction. Canadian astronaut Dave Williams will soon follow MacLean to the International Space Station. Williams will perform three spacewalks on mission STS-118, currently slated to launch in June 2007.