The Nimbus 7 observatory carries three identical tape recorders, one classified as a redundant unit. Each recorder is capable of recording either DIP or ZIP data, but not both simultaneously. In a normal recording operation, one recorder records 25 kbs data from the DIP for periods of 100 to 257 minutes and then reproduces it in reverse direction at a rate of 800 kbs. Normally, one recorder will be used for recording DIP data and another is used for recording ZIP data. Each recorder has a total record capacity of 305 minutes of DIP data recorded at 25 kbs or 9.56 minutes of ZIP data at 800 kbs.
Data are played back at a rate of 800 kbs for either the DIP or ZIP with a lapse rate of 9.56 minutes for a full tape. Less time is required if less than a full tape has been recorded. A three-minute rewind mode moves 500 feet of active tape from beginning to end without record, playback or erasure of previously recorded data. In normal operation, one recorder is played back to a receiving station while the other is recording, thus avoiding data loss.