THE RECOVERY AND RESTORATION OF PCM DATA

Abstract

PCM data generated during pre-flight testing and during flight of the Space Shuttle is subject to contamination from many sources. Excessive noise and other interference can hamper attempts to process the data. A previous paper (The Recovery of PCM Telemetry Data in the Presence of Interference Signals, ITC ’82) discussed the sources of interference and the design of equipment to reduce it to acceptable levels. In the intervening period work has proceeded aimed at the total recovery of PCM data regardless of it’s condition. These efforts have been successful and data submerged in noise and previously unrecoverable has been easily processed. In addition, it has been determined that the time/phase relationships of different portions of a PCM wavetrain may be altered during transmission, dubbing, etc. This phenomena when it takes place makes it impossible to process the data without excessive dropouts. Equipment has been designed to correct this problem.