Recovery of PCM telemetry data in the presence of interference signals

PCM data is recorded on magnetic tape on-board the Space Shuttle during flight. After the vehicle has landed, these tapes are played back into a laboratory tape recorder and copies or dubs are made. PCM data from the vehicle is also recorded during manufacture and preflight testing and dubs of these tapes are made. Signals from other electronic equipment at the recording site can be picked up and mixed with the PCM data. This can cause dropouts (loss of data) during playback. The low frequencies are easily removed by filtering but higher frequencies that lie in the same range as the data cannot be removed by filtering. Methods for dealing with this problem have been worked out with some success. The work has just started. Some of the results are described here.