From: Johnson Space Center
Posted: Wednesday, March 25, 2009
Late Inspection LDRI Mode
During STS-126, the LDRI unit had occurrences of as much as 80 seconds of video loss during Late Inspection. The most noticeable occurrence happened during Port wing scan 1 when panel 8 and 1/2 of panel 9 were missed but were compensated for on another scan. Ground troubleshooting has just recently been able to recreate the anomaly and narrowed down the problem to video circuitry. A root cause has yet to be determined but is believed to be a thermal issue with warmup/cool down of the LDRI when transitioning in and out of Mode 6, which is when the biggest dropouts have historically occurred. During your FD2 inspections, there were a total of 5 frames of dropouts, all of which did not impact LDRI data.
To decrease the chance of this anomaly occurring, we will be changing the late inspection procedures to keep the LDRI in Mode 6 during the transitions between the wing and nose cap surveys. The LDRI will be at least 13 feet from the crew cabin during the SRMS operations, and is eye-safe outside of 6 feet, so there are no concerns with the laser being activated.
If LDRI video is lost for more than a few seconds during late inspection, we will ask you to pause the auto sequence and wait for the video to recover before proceeding. Worst-case, you may be asked to back-up to a previous point and restart the inspections to ensure adequate coverage. If you happen to notice that the LDRI video is bad while scanning, please pause the auto sequence and check MCC. The following changes keep the LDRI in Mode
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