posted 08-02-2005 01:22 AM               

Is there some kind of data or telemetry included in the video signal that would cause the line.

I think I read something on the net about 10 years ago that said it had to do with the timing of the video siganl against the timing of something else onboard. However, I could not find that reference again.

Thanks for any info.

posted 08-23-2005 01:33 AM               

It is because the RCU (Remote Control Unit) and VSU (Video Switching Unit) insert remote control and timecode data to be able to control the cameras from different areas in the orbiter and from mission control. However, the VTR and newer cameras/camcorders are not synced with the VSU and RCU. Therefore, the data for remote-controlling and inserting timecode shows up in the video field (as a horizontal line) instead of during the video blanking period. The line is not always present because the remote control/timecode can be switched off.