Orbiter Boom Sensor System
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The Orbiter Boom Sensor System (OBSS) is a 50 foot boom terminating in an instrumentation package that can be grappled by the Remote Manipulator System of NASA's Space Shuttle spacecraft. The OBSS is used to scan the leading edges of the wings, the nose cap, and the crew compartment after each lift-off and before each landing. If flight engineers suspect potential damage to other areas, as evidenced in imagery captured during lift-off or the rendezvous pitch maneuver, then additional regions may be scanned.
The OBSS was introduced to the shuttle fleet with mission STS-114, the "Return to Flight" mission executed by Discovery, to inspect the shuttle for damage to the heatshield, officially called Thermal Protection System (TPS), that could jeopardize the shuttle during re-entry. The creation of the OBSS was prompted by the Space Shuttle Columbia disaster, which resulted in the destruction of a shuttle due to damage inflicted to the heatshield during lift-off. If critical damage is detected with the OBSS, the crew may attempt to correct it via a spacewalk, or if the damage is not repairable, dock with the International Space Station, where the crew would wait until a rescue mission (designation scheme STS-3xx) can take place. OBSS systems for all 3 remaining orbiters were manufactured relatively quickly, mostly because some spare parts of the Canadarm system were used.
[edit] Instruments
The OBSS has 2 instrumentation packages. Sensor package 1 consists of Laser Dynamic Range Imager (LDRI) and an Intensified Television Camera (ITVC). Sensor package 2 is Laser Camera System (LCS) and a digital camera (IDC). The sensors can resolve at a resolution of few millimeters, and can scan at a rate of about 2.5 inches (6.3 centimeters) per second.
It also has handrails for astronauts so that they can perform repair work under the shuttle.
[edit] STS-120 ISS repair
During STS-120 the OBSS was used as an extension boom for the space station's Canadarm2, something it was never designed to do. During this mission the P6 solar array had become damaged during the redeploy. Canadarm2 grabbed the arm on its center grapple fixture and then astronaut Scott E. Parazynski was mounted at the end of the boom to make the repair. Because Canadarm2 is unable to power the OBSS it was without power many hours more than it was designed to handle, but because it was heated up considerably before the start of the repair it stayed undamaged.
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