on the order of 10 g were required to cause damage. Michael Fossum and Piers Sellers performed a -hour space walk. They evaluated the use of the Orbital Boom Sensor System extension to Shuttle's Canadarm as a work platform in case repairs are needed to the shuttle. The first step was to attach the foot restraints to the arm. First Piers Sellers worked alone; then Mike Fossum joined him – when both are on the arm they attempted increasingly vigorous operations that simulate various potential repair scenarios. Initial reports from Michael Fossum and Piers Sellers suggested that the boom was damping out motion rapidly, making it a good work platform. Piers Sellers said at one point: "I felt almost no motions at all, just a few inches each way, very few motions". When standing on the boom while it was moving they described it as very smooth. Fossum had a problem with his long safety tether, which was damaged after he made a mistake; not realising he had left the tether in a locked position, he expected it to be automatically drawn tight. Upon realising the mistake Fossum said: "Oh no! ... That's embarrassing". The damaged tether had to be switched for a spare. The other major task was to make safe a cable cutter on the ISS's mobile transporter. The morning's flight plan revision emailed up to the crew contained the following request: One of the day's highlights was a press conference from orbit, with questions from JSC, KSC, and the ESA. Robotics operations continued, with the Canadarm2 releasing the mobile transporter from one end, while remaining attached with the other end to the Destiny module in preparation for the following day's work on the mobile transporter system. Other preparations for the second space walk continued, including the setting up of equipment, and cameras. Additionally a new spacesuit being delivered to the ISS was transferred and underwent "checkout" procedures. Sellers and Fossum performed a 6-hour, 47-minute space walk. They deployed a spare pump module and replaced a reel of umbilical cable carrying power, data and video for operating the station's Mobile Transporter rail car. The astronauts also continued cargo transfers between the shuttle, the International Space Station and the Leonardo multi-purpose logistics module. Leonardo arrived with more than 7,400 pounds of equipment and supplies for the station. Leonardo will be returned Friday to the payload bay packed with more