The in-orbit inspection of Space Shuttle Discovery last week went smoothly and provided NASA’s mission management team (MMT) with data suggesting it will be safe for the orbiter to re-enter the atmosphere. In-orbit inspection of the vehicle, using the 15.25m (50ft) Orbiter Boom Sensor System (OBSS) with its robotic arm extension, began with the nose cap on the morning of 27 July, flight day two. This followed the hand-held camera survey of the external tank (ET) as it fell away from Discovery at about 9min after launch.

The OBSS carried out the surveys while attached to the Shuttle’s remote manipulator system (RMS) – a robotic arm – by an electrical grapple fixture. Both are made by Canadian manufacturer MD Robotics.

The OBSS arm extension consists of two linked 6.1m-long composite tubes made as RMS replacement parts. The OBSS has a monochrome intensified television camera, a laser camera and a laser dynamic range imager (LDRI), which provides three-dimensional topography data. Its resolution is a few millimetres at a distance of 10m.

On 27 July the vehicle’s upper surfaces and crew cabin were surveyed, with camera footage played back afterwards for analysis. On the morning of 28 July, Discovery carried out the rendezvous pitch manoeuvre, a back-flip, at 183m from the International Space Station (ISS). The ISS crew photographed the Shuttle with high-magnification digital cameras during the back flip.

The Shuttle then docked with the ISS. Once docked, the RMS cannot move the OBSS out of the payload bay as the station obstructs it. So the ISS Space Station Remote Manipulator System removed the OBSS and handed it to Discovery’s RMS. This enabled the thermal protection system to be surveyed using the LDRI on 29 July.

It was used to scan areas of damages that were identified as being of interest by the MMT, from images captured during the ascent and subsequent OBSS survey. Six areas, including a chipped nose gear door tile, are potential candidates for a close-up inspection as Flight International went to press. The damage assessment is carried out by NASA’s systems engineering and integration office. Under current plans, the MMT may decide to order an EVA to attempt to repair any damage on 31 July, flight day six.

Source: Flight International