271 DAY IN THE LIFE: IN-FLIGHT MAINTENANCE CHAPTER 16 “Can You See It Now?” The Finding Ready to Latch section of the Structures and Mechanisms chapter provides details on the Centerline Berthing Camera System (CBCS). The heart of the CBCS is a video camera that looks through a hatch window at an incoming space station module or cargo vehicle. The camera view is important in ensuring precise alignment of the new module before it can be attached to the ISS. On Space Transportation System (STS)-102/ISS-5A.1 (2000), the CBCS video signal was to be sent to the aft flight deck of the orbiter to assist the shuttle crew in installing the Multi-Purpose Logistics Module (MPLM) for the first time. This would also be the first time the CBCS signal was sent from Node 1 through the newly installed US Laboratory, through Pressurized Mating Adapter (PMA)2, to a visiting orbiter (Space Shuttle Discovery, in this case). The video monitor on the aft flight deck remained black after everything was connected and power was applied to the camera for a checkout on the day prior to MPLM installation. Thankfully, the CBCS checkout had been scheduled to occur the day prior to the MPLM installation, which gave the ground teams time to troubleshoot overnight. By the following morning, the crew had a fresh set of Diagnostic Maintenance procedures that could be used to pinpoint the source of the problem. The crew first used one of the ISS laptops as a portable video monitor. With some spare cabling, the crew connected the laptop to the CBCS camera. This setup enabled crew members to see the video and confirm the camera was functioning properly. For the CBCS to be fully operational, the camera needed to receive a return (sync) video signal from the orbiter. Yet, when the crew connected the laptop to the return line from the orbiter, no video was displayed, thereby indicating a video cable problem between Node 1 and the orbiter. After ruling out any problem with the CBCS, the ground team looked at ISS video system drawings. It turned out that although PMA3 (used successfully with CBCS on STS-98/ISS-5A, months earlier) and PMA2 are nearly identical, the video wiring is not. The video and sync lines were inadvertently crossed on the PMA2 drawings. This cross wiring was dutifully implemented according to the drawings when PMA2 was built. This problem was not caught in ground testing because the testing did not use a setup that requires successful receipt of the video signal on the sync line, which is something the CBCS requires. Once the problem was identified, developing a solution was simple. The video lines between Node 1 and the orbiter needed to be “uncrossed.” The crew created two jumper wires using the on-board pin kit, which is a collection of spare wire and electrical contacts (pins and sockets). These jumpers allowed the crew to cross the video and sync lines in the US Laboratory so that the wiring for the PMA2 would uncross it. This option was possible because the ISS wire bundles and harnesses have numerous connectors located throughout the spacecraft that are readily accessible to the crew. When necessary, the crew can disconnect a wire bundle and use a connector to perform diagnostic troubleshooting on hardware or, in the case of the CBCS, correct an error in design and manufacturing. The result: Successful CBCS video was received on the flight deck in time to complete the first installation of an MPLM on the ISS. A more permanent jumper was manufactured and flown on STS-100/ISS-6A a few months later, and installed in place of the temporary pin kit jumpers. That jumper harness remained installed until Node 2 (Harmony) was installed on STS-120/ISS-10A (2007). Node 2 was built with crossed video wiring such that it would correct the wiring problem in PMA2 without the need for the extra jumper in the US Laboratory. “Where’s The Leak?” Air leaks on a spacecraft are usually bad news because the air needs to stay inside for the crew to breathe. However, when an EVA (i.e., spacewalk) takes place, the airlock must be able to be depressurized to vacuum. When the normally pressurized airlock and its systems are at vacuum, there must also be certainty that no cabin air from elsewhere on the ISS leaks into the depressurized airlock. In the early years of the ISS, both types of “things you don’t want” occurred i.e., a small leak of cabin air to space, and a small leak of cabin air into the airlock when it was at a lower pressure than the rest of the space station. In both cases, a diagnostic tool was required to help the crew find the source of the leak and stop it.