UTC (05:11 EDT), which was 30 minutes earlier than planned. Once the hatches were opened the STS-131 crew got a safety briefing from the station crew, then began to transfer items that would be needed for later in the day and early on flight day 4. Two items that were transferred were the two EMUs that will be used for the three spacewalks. The crew also completed a grapple of the Orbiter Boom Sensor System (OBSS) with the Space Station Remote Manipulator System (SSRMS) also known as Canadarm2. Once the OBSS was grappled it was unberthed from the starboard sill of the space shuttle payload bay, and handed off to the SRMS. Throughout the day, after docking to the station, the shuttle crew began downlinking all of the inspection video from flight day 2, and launch imagery and video. April 8 (Flight Day 4 – MPLM ingress) On flight day 4, Stephanie Wilson and Naoko Yamazaki grappled and berthed the Multi-purpose Logistics Module (MPLM) Leonardo. The MPLM was berthed to the station at 04:24 UTC (00:24 EDT). The hatches were opened by station flight engineer Soichi Noguchi and shuttle mission specialist Clayton Anderson at 11:58 UTC (07:58 EDT). The joint STS-131/Expedition 23 crews began transferring cargo from the MPLM, with the first item being a Rate Gyro Assembly (RGA) which will be replaced on the first spacewalk of the mission. During flight day 4, commander Alan Poindexter did several in-flight interviews. Commander Poindexter was joined by mission specialists Rick Mastracchio and Stephanie Wilson. The interviews were with the Tom Joyner Radio Show, WVIT-TV and Fox News Radio. At the end of the day, Mastracchio and Anderson entered the Quest airlock and begin breathing pure oxygen for an hour, while the atmospheric pressure inside the airlock was lowered to 10.2 psi. This procedure is known as the pre-breathe protocol and is done before every spacewalk, to purge nitrogen from the blood stream and prevent decompression sickness. April 9 (Flight Day 5 – EVA 1) Flight day 5 saw the completion of the first spacewalk by Rick Mastracchio and Clayton Anderson. The pair released the new ammonia tank assembly for transfer to station for installation on a later spacewalk. They also removed an experiment from outside on the Kibo Exposed Facility, replaced a Rate Gyro Assembly (RGA) and performed several get-ahead tasks. The spacewalking pair was assisted by the SSRMS which was